The Monthly Digest – Food Waste – February & March 2018

Food Waste and by-products

R & D abstracts – February & March 2018

Deep eutectic solvents pretreatment of agro-industrial food waste (research)

Waste biomass from agro-food industries are a reliable and readily exploitable resource. From the circular economy point of view, direct residues from these industries exploited for production of fuel/chemicals is a winning issue, because it reduces the environmental/cost impact and improves the eco-sustainability of productions. The present paper reports recent results of deep eutectic solvent (DES) pretreatment on a selected group of the agro-industrial food wastes (AFWs) produced in Europe. In particular, apple residues, potato peels, coffee silverskin, and brewer’s spent grains were pretreated with two DESs, (choline chloride–glycerol and choline chloride–ethylene glycol) for fermentable sugar production. Pretreated biomass was enzymatic digested by commercial enzymes to produce fermentable sugars. Operating conditions of the DES pretreatment were changed in wide intervals. The solid to solvent ratio ranged between 1:8 and 1:32, and the temperature between 60 and 150 °C. The DES reaction time was set at 3 h. Optimal operating conditions were: 3 h pretreatment with choline chloride–glycerol at 1:16 biomass to solvent ratio and 115 °C. Moreover, to assess the expected European amount of fermentable sugars from the investigated AFWs, a market analysis was carried out. The overall sugar production was about 217 kt yr−1, whose main fraction was from the hydrolysis of BSGs pretreated with choline chloride–glycerol DES at the optimal conditions. The reported results boost deep investigation on lignocellulosic biomass using DES. This investigated new class of solvents is easy to prepare, biodegradable and cheaper than ionic liquid. Moreover, they reported good results in terms of sugars’ release at mild operating conditions (time, temperature and pressure).

Procentese A et al (2018) Biotechnology for Biofuels 11:37

Engineering yeast for utilization of alternative feedstocks (research)

Realizing the economic benefits of alternative substrates for commodity chemical bioproduction typically requires significant metabolic engineering of common model organisms, such as Saccharomyces cerevisiae. A growing toolkit is enabling engineering of non-conventional yeast that have robust native metabolism for xylose, acetate, aromatics, and waste lipids. Scheffersomyces stipitis was engineered to produce itaconic acid from xylose. Yarrowia lipolytica produced lipids from dilute acetate at over 100 g/L. Cutaneotrichosporon oleaginosus was engineered to produce omega-3 fatty acids and recently was shown to accumulate nearly 70% lipids when grown on aromatics as a carbon source. Further improvement to toolkits for genetic engineering of non-conventional yeast will enable future development of alternative substrate conversion to biochemicals.

Yaguchi A et al (2018) Current Opinion in Biotechnology 53:122-129

Conversion of lignocellulosic agave residues into liquid biofuels using an AFEX™-based biorefinery (research)

Agave-based alcoholic beverage companies generate thousands of tons of solid residues per year in Mexico. These agave residues might be used for biofuel production due to their abundance and favorable sustainability characteristics. In this work, agave leaf and bagasse residues from species Agave tequilana and Agave salmiana were subjected to pretreatment using the ammonia fiber expansion (AFEX) process. The pretreatment conditions were optimized using a response surface design methodology. We also identified commercial enzyme mixtures that maximize sugar yields for AFEX-pretreated agave bagasse and leaf matter, at ~ 6% glucan (w/w) loading enzymatic hydrolysis. Finally, the pretreated agave hydrolysates (at a total solids loading of ~ 20%) were used for ethanol fermentation using the glucose- and xylose-consuming strain Saccharomyces cerevisiae 424A (LNH-ST), to determine ethanol yields at industrially relevant conditions. Low-severity AFEX pretreatment conditions are required (100–120 °C) to enable efficient enzymatic deconstruction of the agave cell wall. These studies showed that AFEX-pretreated A. tequilana bagasse, A. tequilana leaf fiber, and A. salmiana bagasse gave ~ 85% sugar conversion during enzyme hydrolysis and over 90% metabolic yields of ethanol during fermentation without any washing step or nutrient supplementation. On the other hand, although lignocellulosic A. salmiana leaf gave high sugar conversions, the hydrolysate could not be fermented at high solids loadings, apparently due to the presence of natural inhibitory compounds. These results show that AFEX-pretreated agave residues can be effectively hydrolyzed at high solids loading using an optimized commercial enzyme cocktail (at 25 mg protein/g glucan) producing > 85% sugar conversions and over 40 g/L bioethanol titers. These results show that AFEX technology has considerable potential to convert lignocellulosic agave residues to bio-based fuels and chemicals in a biorefinery.

Flores-Gomez CA et al (2018) Biotechnology for Biofuels 11 :7

Biovalorization of brewers’ spent grain for the production of laccase and polyphenols (research)

Brewers’ spent grain (BSG) is the main solid by-product of the brewing process and is typically disposed of as cattle feed. In this study, BSG was evaluated as a substrate for the production of polyphenols and the lignin-degrading enzyme laccase using fungal solid-state fermentation by Trametes versicolor. Laccases are finding increasing applications in the food industry and polyphenols have benefits for human health. After 14 days of fermentation with T. versicolor, there was a 3.4-fold increase in the extraction of total polyphenols compared with untreated BSG. Using BSG as the sole source of carbon and nitrogen, maximum laccase activity was achieved after seven days of treatment with an activity of 560 U/L. Based on these results, BSG is suggested to be a good lignocellulose waste material to produce value-added products such as the enzyme laccase and polyphenols.

Tisma M et al (2018) Journal of the Institute of Brewing (in press)

Valorisation of food and beverage waste via saccharification for sugars recovery (research)

Valorisation of mixed food and beverage (F&B) waste was studied for the recovery of sugars via saccharification. Glucoamylase and sucrase were employed to hydrolyse the starch and sucrose present in the mixed F&B waste because of the high cost-effectiveness for such recovery. The Michaelis-Menten kinetics model suggests that preservatives and additives in beverages did not inhibit glucoamylase and sucrase during saccharification. High levels of glucose (228.1 g L−1) and fructose (55.7 g L−1) were efficiently produced within 12 h at a solid-to-liquid ratio of 37.5% (w/v) in 2.5 L bioreactors. An overall conversion yield of 0.17 g sugars per g of mixed F&B waste was obtained in mass balance analysis. Lastly, possible industrial applications of the sugar-rich hydrolysate and by-products are discussed. This study is believed to cast insights into F&B waste recycling via biotechnology to produce high-value added products to promote the establishment of a circular bio-economy.

Kwan TH et al (2018) Bioresource Technology 255:67-75

Electric energy production from food waste: Microbial fuel cells versus anaerobic digestion (research)

A food waste resourceful process was developed by integrating the ultra-fast hydrolysis and microbial fuel cells (MFCs) for energy and resource recovery. Food waste was first ultra-fast hydrolyzed by fungal mash rich in hydrolytic enzymes in-situ produced from food waste. After which, the separated solids were readily converted to biofertilizer, while the liquid was fed to MFCs for direct electricity generation with a conversion efficiency of 0.245 kWh/kg food waste. It was estimated that about 192.5 million kWh of electricity could be produced from the food waste annually generated in Singapore, together with 74,390 tonnes of dry biofertilizer. Compared to anaerobic digestion, the proposed approach was more environmentally friendly and economically viable in terms of both electricity conversion and process cost. It is expected that this study may lead to the paradigm shift in food waste management towards ultra-fast concurrent recovery of resource and electricity with zero-solid discharge.

Xin XD et al (2018) Bioresource Technology 255:281-287

The Monthly Digest – Food Waste – April & May 2018

Food Waste and by-products

R & D abstracts – April & May 2018

Food waste as a source of value‐added chemicals and materials: a biorefinery perspective (review)

As the availability of fossil‐based resources declines, there is an impending necessity of finding alternative feedstock able to secure the production of fuels and chemicals. Exploitation of biomass as renewable source of chemicals is an attractive possibility, in particular the one derived from food waste (FW). Every year, large amounts of waste are generated within or at the end of the food supply chain at the consumers use stage and hence its valorisation attracts great attention. FW has proven a valuable feedstock for its exploitation to produce a wide array of intermediates and products with promising applications in industry, owing to their similar performance with respect to established products. These include organic acids and furans (generally used as platform chemicals to further products); polymers like bacterial cellulose, polyhydroxyalkanoates or chitin; biosurfactants; biolubricants; or nanoparticles. This overview covers the latest trends in chemical, enzymatic and biotechnological processes reported in literature on the production of these chemicals and materials, with a focus on the use of FW as raw material.

Esteban J and Ladero M (2018) International Journal of Food Science and Technology 53:1095-1108

Techno-economic and profitability analysis of food waste biorefineries at European level (review)

Food waste represents a potential source to produce value-added materials replacing the use of virgin ones. However, the use of food waste as feedstock in biorefineries is still at an early stage of development and studies assessing its economic viability at large scale are lacking in the literature. This paper presents a techno-economic and profitability analysis of four food waste biorefineries that use wastes from tomato, potato, orange, and olive processing as feedstock. The study includes the assessment of potentially available quantities of those waste flows in Europe. Due to the low technology readiness level of this kind of biorefineries, a screening methodology to estimate the investment and manufacturing costs as well as two profitability ratios (the return on investment and the payback time) was adopted. Results show that not all the waste feedstocks have the same potential. The most profitable options are those related to implementing fewer plants, namely concentrating the production and capitalising on economies of scale while being at risk of increasing externalities, e.g. due to logistics of the feedstocks.

Cristobal J et al (2018) Bioresource Technology 259:244-252

Valorisation of fruit and vegetable waste from open markets for the production of 2,3-butanediol (research)

The bacterial strain Enterobacter ludwigii FMCC 204 was selected as the most efficient 2,3-butanediol (BDO) producer among five strains when cultivated on glucosefructosemannosearabinosexylosegalactose and sucrose in shake flask cultures. Plums, apples and pears were used for the production of fermentation medium via sequential maceration, suspension in water and centrifugation to collect the supernatant. Sugar production from mixed vegetables was evaluated via sulphuric acid treatment leading to 65.8% (w/w) of hemicellulose hydrolysis yield at initial solid concentrations of 50 g/L (on a dry basis) treated with 3% (v/v) H2SO4. Fed-batch cultures of E. ludwidgii on fruit derived feedstock resulted in BDO concentration, yield and productivity of 50 g/L, 0.4 g/g and 0.41 g/L/h. BDO production from vegetable waste hydrolysates via fed-batch cultures led to BDO concentration of 17.6 g/L. This study demonstrated that fruit and vegetable wastes from open markets can be used as fermentation feedstocks for BDO production.

Liakou V et al (2018) Food and Bioproducts Processing 108:27-36

Experimental and feasibility assessment of biogas production by anaerobic digestion of fruit and vegetable waste from Joburg Market (research)

Substrate-induced instability of anaerobic digestion from fruit and vegetable waste (FVW) results in low biogas yield. In this study, substrate management through fruit to vegetable mix ratio in a two-stage semi-continuous digester was investigated as a pathway for optimality of yield. The experiment conducted over 105 days with 62.52 kg of FVWs sourced from Joburg Market, South Africa showed that a stable process was achieved at a fruit to vegetable waste mix ratio of 2.2:2.8. At this ratio, optimal organic loading rate ranged between 2.68 and 2.97 kg VS/m3-d which resulted in a specific biogas yield of 0.87 Nm3/kg VS with 57.58% methane on average. The results of the experimental study were used as a feasibility assessment for a full-scale 45 tonnes/d plant for Joburg Market considering three energy pathways. The plant will produce 1,605,455 Nm3/y of biogas with the potential for offsetting 15.2% of the Joburg Market energy demand. Conversion of all biogas to biomethane was the most economically attractive energy pathway with a net present value of $2,428,021, an internal rate of return of 16.90% and a simple payback period of 6.17 years. This route avoided the greenhouse gas emission of 12,393 tonnes CO2, eq. The study shows that the anaerobic digestion of FVWs as sole substrate is possible with financial and environmental attractiveness.

Masebinu SO et al (2018) Waste management 75:236-250

Process design and techno-economic analysis of an integrated mango processing waste biorefinery (research)

This study evaluated costs and profitability associated with mango processing waste biorefinery plant with the goal of generating wealth from waste. Three pathways were evaluated (i) Only Pectin recovery (PEP) (ii) Pectin and Seed Oil recovery (PSEP), and (iii) whole biorefinery with multiple products (WMB). A plant capacity of 10 tons/h was considered as a base case for analysis. Effect of biomass feed composition on product yields were also reported in this study. The PSEP was found to be the best alternative for mango waste utilization. The NPV, IRR and PEP were $41 million, 34% and 2.4 years, respectively. In case of PEP and WMB, NPVs were $14.2 and $43.2 million; IRRs were 20% and 26%, and PBP were 4.2 and 3.4 years, respectively. Sensitivity analysis showed that plant capacity, plant operating days, and raw material composition were most important factors that influenced plant economics. Selling price of main product i.e. pectin had a major influence on plant economics. The effect of raw material price fluctuation however, did not influence plant economics significantly.

Arora A et al (2018) Industrial Crops and Products 116:24-34

Anaerobic digestion of orange peel in a semi-continuous pilot plant: An environmentally sound way of citrus waste management in agro-ecosystems (research)

The management of residues of citrus processing involves economic and environmental problems. In particular, the uncontrolled disposal of citrus processing waste near production sites can have heavy impacts on air, soil, surface water bodies and groundwater. Anaerobic digestion has been proposed as a viable alternative for citrus waste valorisation, if some problems, linked to the biochemical processes, are overcome. Although many experimental tests have studied the inhibitory effects of the high essential oil content of orange peel on biomethanisation processes, fewer experiences have been carried out in continuous or semi-continuous pilot digesters, more similar to the full-scale biogas plants, using real orange peel. This study has evaluated the methane production through anaerobic digestion of industrial orange peel using a pilot plant (84 L) with semi-continuous feeding at increasing Organic Loading Rates (OLR) and essential oil (EO) supply rates (EOsr) until the complete process inhibition. Under mesophilic conditions, the highest daily specific methane yield was achieved at OLR of 1.0 gTVS L−1 d−1 and EOsr of 47.6 mg L−1 d−1. Partial inhibition of the anaerobic digestion was detected at OLR and EOsr of 1.98 gTVS L−1 d−1 and 88.1 mg L−1 d−1, respectively and the process irreversibly stopped when OLR and EOsr reached 2.5 gTVS L−1 d−1 and 111.2 mg L−1 d−1, respectively. Under thermophilic conditions, the cumulative methane production (0.12 L gTVS−1) was about 25% of that under mesophilic conditions (0.46 L gTVS−1). The thermophilic digestion was completely inhibited at lower OLR (1.98 gTVS L−1 d−1) and EOsr (88.1 mg L−1 d−1) compared to mesophilic conditions. This study confirmed the suitability of anaerobic digestion of orange peel for biomethane production (provided that the right management of the process is set), in view of an environmentally sound way of agricultural residues management in agro-ecosystems.

Zema DA et al (2018) Science of the Total Environment 630:401-408

The Monthly Digest – Aromas and flavours – April & May 2018

Aromas and flavours

R & D abstracts – April & May 2018

Biogeneration of aroma compounds (review)

Aroma compounds may be recovered from natural sources, produced by chemical synthesis or by biotechnological means. The latter approach has faced constant growth and it is expected to continue expanding in the future. This study reviews the recent advances in the biogeneration of aroma compounds, focusing on the microbial production (either by de novo synthesis or by biotransformation of widely available substrates) of the most commercially relevant compounds.

Sales A et al (2018) Current Opinion in Food Science (in press)

Production of vanillin from lignin: The relationship between β-O-4 linkages and vanillin yield (research)

Lignin is the renewable source of aromatics in nature, and the conversion of lignin into vanillin is very attractive. However, the vanillin yield is closely related to the resource of lignin and its isolation process, and relatively low yield of vanillin is always obtained from lignin. In order to improve the vanillin yield from lignin, in this work, the relationship between lignin linkages and vanillin yield was explored. Five lignins (kraft lignin, alkali lignin, lignosulfonate, and two enzymatic lignins) and various lignin model compounds (monomers, dimers, and polymers) were characterized by NMR spectroscopy and oxidized to prepare vanillin. Results indicated that the interunit linkages of the lignin had a significant influence on the vanillin yield. The more β-O-4 linkages in lignin, the higher yield of corresponding aldehydes was obtained. It is believed that the vanillin yield can be significantly improved by using lignins with high content of β-O-4 linkages.

Wang Y et al (2018) Industrial Crops and Products 116:116-121

The Monthly Digest – Aromas and flavours – February & March 2018

Aromas and flavours

R & D abstracts – February & March 2018

Biosynthesis and production of sabinene: current state and perspectives (review)

Sabinene is an important naturally occurring bicyclic monoterpene which can be used as flavorings, perfume additives, fine chemicals, and advanced biofuels. Up to now, this valuable terpene is commercially unavailable since there is no applicable manufacturing process. Microbial synthesis can be a promising route for sabinene production. In this review, we summarize knowledge about the metabolic pathway and key enzymes for sabinene biosynthesis. Recent advances that have been made in production of sabinene by microbial fermentation are highlighted. In these studies, researchers have identified the general synthetic pathway of sabinene from simple intermediate metabolites. Sabinene synthases of different origins were also cloned and characterized. Additionally, heterologous systems of the model microbes Escherichia coli and Saccharomyces cerevisiae were constructed to produce sabinene. This review also suggests new directions and attempts to gain some insights for achieving an industrial level production of sabinene. The combination of traditional molecular biology with new genome and proteome analysis tools will provide a better view of sabinene biosynthesis and a greater potential of microbial production.

Cao Y et al (2018) Applied Microbiology and Biotechnology 102:1535-1544

Bioflavoring by non-conventional yeasts in sequential beer fermentations (research)

Non-conventional yeast species have great capacity for producing diverse flavor profiles in production of alcoholic beverages, but their potential for beer brewing, in particular in consecutive fermentations with Saccharomyces cerevisiae, has only poorly been explored. We have screened 17 non-conventional yeast species for production of an appealing profile of flavor esters and phenolics in the first phase of alcoholic fermentation, followed by inoculation with S. cerevisiae to complete the fermentation. For measurement of phenolic compounds and their precursors we developed an improved and highly sensitive methodology. The results show that non-conventional yeast species possess promising potential for enhancement of desirable flavors in beer production. Notable examples are increasing isoamyl acetate (fruity, banana flavor) by application of P. kluyverii, augmenting ethyl phenolic compounds (spicy notes) with Brettanomyces species and enhancing 4-vinyl guaiacol (clove-like aroma) with T. delbrueckii. All Pichia strains also produced high levels of ethyl acetate (solvent-like flavor). This might be selectively counteracted by selection of an appropriate S. cerevisiae strain for the second fermentation phase, which lowers total ester profile. Hence, optimization of the process conditions and/or proper strain selection in sequentially inoculated fermentations are required to unlock the full potential for aroma improvement by the non-conventional yeast species.

Holt S et aal (2018) Food Microbiology 72:55-66

Microbe participation in aroma production during soy sauce fermentation (research)

Soy sauce is a traditional Japanese fermented seasoning that contains various constituents such as amino acids, organic acids, and volatiles that are produced during the long fermentation process. Although studies regarding the correlation between microbes and aroma constituents have been performed, there are no reports about the influences of the microbial products, such as lactic acid, acetic acid, and ethanol, during fermentation. Because it is known that these compounds contribute to microbial growth and to changes in the constituent profile by altering the moromi environment, understanding the influence of these compounds is important. Metabolomics, the comprehensive study of low molecular weight metabolites, is a promising strategy for the deep understanding of constituent contributions to food characteristics. Therefore, the influences of microbes and their products such as lactic acid, acetic acid, and ethanol on aroma profiles were investigated using gas chromatography/mass spectrometry (GC/MS)-based metabolic profiling. The presence of aroma constituents influenced by microbes and chemically influenced by lactic acid, acetic acid, and ethanol were proposed. Most of the aroma constituents were not produced by adding ethanol alone, confirming the participation of yeast in aroma production. It was suggested that lactic acid bacterium relates to a key aromatic compound, 2,5-dimethyl-4-hydroxy-3(2H)-furanone. However, most of the measured aroma constituents changed similarly in both samples with lactic acid bacterium and acids. Thus, it was clear that the effect of lactic acid and acetic acid on the aroma profile was significant.

Harada R et al (2018) Journal of Bioscience and Bioebgineering (2018)

The Monthly Digest – Food Waste October 2017

Food wastes and by-products
R & D abstracts – October 2017

 

Putting together the puzzle of consumer food waste: Towards an integral perspective (review)

Although consumer food waste has increasingly received attention in both the public and the scientific domain, its complex nature is far from unraveled. This study aimed to contribute to an integral understanding of possible causal pathways of consumer food waste, by means of a configurative systematic literature review of potential factors of consumer food waste. Insights from 59 scientific articles have been systematically analysed and synthesised. Consumer food waste research is characterised by fragmentation, lack of differentiation, and a relative scarcity of explanatory research into causal mechanisms. Potential factors of consumer food waste have been identified and categorised into behavioural, personal, product and societal factors and subclusters of these categories. On the basis of a synthesised overview of 116 factors, a framework has been developed that conceptualises the generation of consumer food waste in relation to stages of the household food chain. This review sheds light on the context-dependent ways in which proposed factors may be related to food waste and the possibility of parallel causal routes. Food waste factors might exert their influence in unexpected, indirect or multiple ways, possibly explaining contradictory findings. They might interact with other factors or form a condition for other factors to play a role, or might be correlated with food waste without playing a causal role. The framework may facilitate an integral and context-sensitive systems perspective, thereby promoting studies that account for the complexity of consumer food waste and intervention programmes that are better targeted.

Roodhuyzen DMA et al (2017) Trends in Food Science & Technology 68:37-50

 

Bioplastics of native starches reinforced with passion fruit peel (research)

Industrial passion fruit juice production generates a large amount of passion fruit waste, which contains about 60% of fibers when dried and could be used as reinforcement of thermoplastic starch. This study aimed to develop an extruded starchy bioplastic reinforced with passion fruit peel (Pfp) (0, 4, 10, 16, and 20%), glycerol (60, 64, 70, 76, and 80 wt%), and starch mix (55% corn and 45% cassava) that were processed at varied screw speeds (66, 80, 100, 120, and 134 rpm). The response surface methodology was applied to analyze the effects of Pfp, glycerol, and screw speed. Mechanical properties, contact angle, and water permeability and solubility were the response variables. Addition of Pfp, up to 4%, improved the bioplastic mechanical properties. High addition of Pfp (16 and 20%) combined with the lowest screw speed (66 rpm) reduced bioplastic water solubility. Water vapor permeability slightly increased with the combination of increasing glycerol content and screw speed. Contact angle was not statically affected by the independent variables. The extrusion showed as an interesting tool that provided greater homogeneity of Pfp incorporated in starch bioplastic, though the mix would benefit from finer Pfp particle size distribution.

Moro TMA et al (2017) Food and Bioprocess Technology 10:1798-1808

Pilot scale fermentation coupled with anaerobic digestion of food waste – Effect of dynamic digestate recirculation (research)

The anaerobic digestion in double stage is a known and adopted system, but the process productivity and optimization still remain an aspect to investigate. The accumulation of organic acids (produced during fermentative metabolism) in the first stage generally decrease the pH below the optimal values (5.5). A pre-evaluation strategy by control charts for further pH control is proposed. The process combines in series the 1st Fermentation process and the 2nd Anaerobic Digestion process, using the recirculation of the anaerobic digestion effluent, rich in buffer agents, to control the pH in the 1st stage. The recycle ratio becomes a further operating parameter that should be properly managed. A proper management as dynamic recirculation flow allows to maintain the pH of the first phase to values higher than 5. Specific hydrogen production, specific methane production and volatile fatty acid production; 170 L/kgTVS at 40% H2, 750 L at 67% CH4 and 14 gCOD/L VFA were obtained respectively.

Gottardo M et al (2017) Renewable Energy 114 B:455-463

Effects of organic composition on the anaerobic biodegradability of food waste (research)

This work investigated the influence of carbohydrates, proteins and lipids on the anaerobic digestion of food waste (FW) and the relationship between the parameters characterising digestion. Increasing the concentrations of proteins and lipids, and decreasing carbohydrate content in FW, led to high buffering capacity, reduction of proteins (52.7–65.0%) and lipids (57.4–88.2%), and methane production (385–627 mLCH4/g volatile solid), while achieving a short retention time. There were no significant correlations between the reduction of organics, hydrolysis rate constant (0.25–0.66 d−1) and composition of organics. Principal Component Analysis revealed that lipid, C, and N contents as well as the C/N ratio were the principal components for digestion. In addition, methane yield, the final concentrations of total ammonia nitrogen and free ammonia nitrogen, final pH values, and the reduction of proteins and lipids could be predicted by a second-order polynomial model, in terms of the protein and lipid weight fraction.

Li Y et al (2017) Bioresource Technology 243:836-845

Effects of organic composition on mesophilic anaerobic digestion of food waste (research)

Anaerobic digestion of food waste (FW) has been widely investigated, however, little is known about the influence of organic composition on the FW digestion process. This study aims to identify the optimum composition ratios of carbohydrate (CA), protein (CP) and lipid (EE) for maintaining high methane yield and process stability. The results show that the CA–CP–EE ratio was significantly correlated with performance and degradability parameters. Controlling the CA–CP–EE ratio higher than 1.89 (CA higher than 8.3%, CP lower than 5.0%, and EE lower than 5.6%) could be an effective way to maintain stable digestion and achieve higher methane production (385–627 mL/g VS) and shorter digestion retention (196–409 h). The CA-CP-EE ratio could be used as an important indicator for digestion performance. To effectively evaluate organic reduction, the concentration and removal efficiency of organic compositions in both solid phases and total FW should be considered.

Li Y et al (2017) Bioresource Technology 244:213-224

The Monthly Digest – Aromas and Flavours October 2017

Aromas and flavours
R & D abstracts – October 2017

Japan Flavour and Fragrance Materials Association’s (JFFMA) safety assessment of food-flavouring substances uniquely used in Japan that belong to the class of aliphatic primary alcohols, aldehydes, carboxylic acids, acetals and esters containing additional oxygenated functional groups (review)

We performed a safety evaluation using the procedure devised by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) of the following four flavouring substances that belong to the class of ‘aliphatic primary alcohols, aldehydes, carboxylic acids, acetals, and esters containing additional oxygenated functional groups’ and are uniquely used in Japan: butyl butyrylacetate, ethyl 2-hydroxy-4-methylpentanoate, 3-hydroxyhexanoic acid and methyl hydroxyacetate. Although no genotoxicity study data were found in the published literature, none of the four substances had chemical structural alerts predicting genotoxicity. All four substances were categorised as class I by using Cramer’s classification. The estimated daily intake of each of the four substances was determined to be 0.007–2.9 μg/person/day by using the maximised survey-derived intake method and based on the annual production data in Japan in 2001, 2005 and 2010, and was determined to be 0.250–600.0 μg/person/day by using the single-portion exposure technique and based on average-use levels in standard portion sizes of flavoured foods. Both of these estimated daily intake ranges were below the threshold of toxicological concern for class I substances, which is 1800 μg/person/day. Although no information from in vitro and in vivo toxicity studies for the four substances was available, these substances were judged to raise no safety concerns at the current levels of intake.

Saito K et al (2017) Food Additives & Contaminants, Part A 34:1474-1484

 

A review on enzymatic synthesis of aromatic esters used as flavor ingredients for food, cosmetics and pharmaceuticals industries

Many sectors of industry, mainly food, cosmetics and pharmaceutics, have increased their interest in esters due to their flavor property. Flavor esters that possess an aromatic ring in their molecular structure are also known as aromatic esters. These esters are widely found in nature (fruits and plants) and the synthetic (i.e. via chemical) and natural routes (i.e. via direct extraction from nature or via biotechnology) are suitable for their biocatalysis. In this context, from the industrial point of view, enzyme-catalyzed reactions are the most economical approach to reach final green products with no toxicity and no harm to human health. The present article gives an overview of the aromatic esters synthesis, considering the main effects in the reaction media conditions and enzymes used. This review also describes applied trends in enzymatic-catalyzed reactions, pointing alternatives to production, like ultrasound-assisted reactions and process optimization of aromatic esters. Furthermore, this work presents perspectives concerning the biological potential of these esters and recent advances in their encapsulation. Lipases play an important role in the aromatic esters production, with several advantages over synthetic route. Lipase-catalyzed reactions usually follow Ping-Pong Bi-Bi or ternary complex (order Bi-Bi) mechanism. The study of the process parameters and their interaction are very important to understand the system optimization and achieve the maximum reaction yield to scale up. Aromatic esters can present some biological activities, in addition to their fragrances, which increases the interest in the encapsulation of these compounds.

Gomes Almeida A et al (2017) Trends in Food Science and Technology 69 A:95-105

Biotransformation of (+)-carvone and (−)-carvone using human skin fungi: A green method of obtaining fragrances and flavours (research)

The synthesis of optically pure compounds is increasingly in demand among the pharmaceutical, fine chemical and agro-food industries, while the importance of chirality in the activity and biological properties of many compounds has previously been established. The aim of the present study was therefore to evaluate the biotransformation capacities of (+)-carvone and (−)-carvone using the fungi Scolecobasidium sp, three lines of Cladosporium sp, Phoma sp, Aureobasidium sp and Epicoccum sp, all obtained from human skin. The seven fungi evaluated were capable of hydrogenating the activated alkene, followed by the reduction of ketone to chiral alcohol, with conversions between 9.5 and 100%, and with diastereomer excess (d.e.) of over 89% of dihydrocarveol when (+)-carvone was used as a substrate. These results demonstrate that the filamentous fungi of human skin are potential biocatalytic tools for obtaining chiral alcohols.

Dos Santos RAM et al (2017) Biocatalysis and Biotransformation (in press)

Use of non-Saccharomyces yeasts and oenological tannin in red winemaking: Influence on colour, aroma and sensorial properties of young wines (research)

Today, many non-Saccharomyces strains have been verified can be positive for the development of wine anthocyanin and aroma in different fermentation scenarios. Moreover, oenological tannins are widely used in wine industry to improve the colour profile and aroma complexity. The aim of this work is to analyze the fermentation characters of non-Saccharomyces strains and investigate the effects of pre-fermentative addition of oenological tannins on the wine components as well as sensory properties. For this purpose, five selected non-Saccharomyces strains and grape seed tannin were used to carry out the different fermentation trials. As a result, the grape seed tannins were less likely to influence growth kinetics of non-Saccharomyces strains. Schizosaccharomyces pombe has been proved can be effective to reduce the malic acid content while increase the level of vinylphenolic pyranoanthocyanin, which is positive for wine colour stability. Pre-fermentative use of oenological tannin was verified could be beneficial for the wines fermented with non-Saccharomyces regarding the improvement of wine colour, anthocyanin composition and the complexity of volatile compounds. Nevertheless, sensory analysis showed that oenological tannin could be less effective to modify the aroma impression of non-Saccharomyces wines.

Chen K et al (2017) Food Microbiology 69:51-63

 

The Monthly Digest – Food Waste September 2017

Food wastes and by-products
R & D abstracts – September 2017
Enhanced polyhydroxyalkanoate (PHA) production from the organic fraction of municipal solid waste by using mixed microbial culture (research)

In Europe, almost 87.6 million tonnes of food waste are produced. Despite the high biological value of food waste, traditional management solutions do not consider it as a precious resource. Many studies have reported the use of food waste for the production of high added value molecules. Polyhydroxyalkanoates (PHAs) represent a class of interesting bio-polyesters accumulated by different bacterial cells, and has been proposed for production from the organic fraction of municipal solid waste (OFMSW). Nevertheless, until now, no attention has been paid to the entire biological process leading to the transformation of food waste to organic acids (OA) and then to PHA, getting high PHA yield per food waste unit. In particular, the acid-generating process needs to be optimized, maximizing OA production from OFMSW. To do so, a pilot-scale Anaerobic Percolation Biocell Reactor (100 L in volume) was used to produce an OA-rich percolate from OFMSW which was used subsequently to produce PHA. The optimized acidogenic process resulted in an OA production of 151 g kg−1 from fresh OFMSW. The subsequent optimization of PHA production from OA gave a PHA production, on average, of 223 ± 28 g kg−1total OA fed. Total mass balance indicated, for the best case studied, a PHA production per OFMSW weight unit of 33.22 ± 4.2 g kg−1 from fresh OFMSW, corresponding to 114.4 ± 14.5 g kg−1 of total solids from OFMSW. PHA composition revealed a hydroxybutyrate /hydroxyvalerate (%) ratio of 53/47 and Mw of 8∙105 kDa with a low polydispersity index, i.e. 1.4. This work showed how by optimizing acidic fermentation it could be possible to get a large amount of OA from OFMSW to be then transformed into PHA. This step is important as it greatly affects the total final PHA yield. Data obtained in this work can be useful as the starting point for considering the economic feasibility of PHA production from OFMSW by using mixed culture.

Colombo B et al (2017) Biotechnology for Biofuels 10:201

 

Treatment of supermarket vegetable wastes to be used as alternative substrates in bioprocesses (research)

Fruits and vegetables have the highest wastage rates at retail and consumer levels. These wastes have promising potential for being used as substrates in bioprocesses. However, an effective hydrolysis of carbohydrates that form these residues has to be developed before the biotransformation. In this work, vegetable wastes from supermarket (tomatoes, green peppers and potatoes) have been separately treated by acid, thermal and enzymatic hydrolysis processes in order to maximise the concentration of fermentable sugars in the final broth. For all substrates, thermal and enzymatic processes have shown to be the most effective. A new combined hydrolysis procedure including these both treatments was also assayed and the enzymatic step was successfully modelled. With this combined hydrolysis, the percentage of reducing sugars extracted was increased, in comparison with the amount extracted from non-hydrolysed samples, approximately by 30% in the case of tomato and green peeper wastes. For potato wastes this percentage increased from values lower than 1% to 77%. In addition, very low values of fermentation inhibitors were found in the final broth.

Diaz AI et al (2017) Waste Management 67:59-66

The Monthly Digest – Aromas and Flavours September 2017

Aromas and flavours
R & D abstracts – September 2017
Microbial diversity of traditional kefir grains and their role on kefir aroma (research)

Kefir grains consist of rich bacterial and fungal microflora responsible for the production of this traditional fermented milk beverage with unique flavour properties. Here, a pyrosequencing approach was applied for the identification of microbial flora of four kefir grains collected from different regions of Turkey and the volatile compounds in kefir samples produced with these grains were determined. Lactobacillus kefiranofaciens presented in all grains at important levels and EnterobacterAcinetobacterEnterococcus and Pseudomonas spp. were observed in traditional kefir grains. The fungal microflora of kefir grains was dominated by yeast species and Dipodascaceae family was dominant and Saccharomyces cerevisiaepresented in all grains. Other yeast species belonging to KazachstaniaCandidaIssatchenkia and Rhodotorula species were also detected in kefir grains. Volatile compounds of kefir samples were also diverse related to the microbial diversity of kefir grains. This study revealed the rich microflora of Turkish kefir grains and their interactions with the aromatic properties of kefir.

Dertli E and çon HA (2017) LWT Food Science and Technology 85A:151-157

 

Influence of different yeast/lactic acid bacteria combinations on the aromatic profile of red Bordeaux wine (research)

The typical fruity aroma of red Bordeaux wines depends on the grape variety but also on microbiological processes, such as alcoholic and malolactic fermentations. These transformations involve respectively the yeast Saccharomyces cerevisiae and the lactic acid bacterium Oenococcus oeni. Both species play a central role in red winemaking but their quantitative and qualitative contribution to the revelation of the organoleptic qualities of wine has not yet been fully described. The aim of this study was to elucidate the influence of sequential inoculation of different yeast and bacteria strains on the aromatic profile of red Bordeaux wine. All microorganisms completed fermentations and no significant difference was observed between tanks regarding the main oenological parameters until 3 months’ aging. Regardless of the yeast strain, B28 bacteria required the shortest period to completely degrade the malic acid, compared to the other strain. Quantification of 73 major components highlighted a specific volatile profile corresponding to each microorganism combination. However, the yeast strain appeared to have a predominant effect on aromatic compound levels, as well as on fruity aroma perception. Yeasts had a greater impact on wine quality and have more influence on the aromatic style of red wine than bacteria.

Gammacurta M et al (2017) Journal of the Science of Food and Agriculture

 

Fed-batch production of vanillin by Bacillus aryabhattai BA03 (research)

Bacillus aryabhattai BA03, a strain isolated in our laboratory, has interesting properties related to the production of natural aromas and flavors. Specifically, we have found that it was able to produce vanillin from ferulic acid (FA). Furthermore, this strain produces high amounts of 4-vinylguaiacol in only 14 h, this being the only intermediate metabolite observed in the process. FA is an inexpensive feedstock for the production of natural value-added compounds when extracted from lignocellulosic wastes. In this study, we optimized the operational conditions (temperature, pH and agitation), medium composition and bioconversion technology (batch or fed-batch) to produce vanillin. In a fed-batch process conducted with just one additional supplementation after 24 h, the maximal concentration of vanillin (147.1 ± 0.9 mg/L) was observed after 216 h (QV = 0.681 mg/L h; YV/fFA = 0.082 mg/mg) after degrading 90.3% FA. In view of our data, we postulate that Bacillus aryabhattai BA03 carries out a decarboxylation of ferulic acid as a metabolic pathway.

Paz A et al (2017) New Biotechnology (in press)

 

Performance of selected P. fermentans and its excellular enzyme in co-inoculation with S. cerevisiae for wine aroma enhancement (research)

This study evaluated aroma enhancement in dry white wines made via a specific Pichia fermentans strain and its excellular enzyme in co-inoculation with Saccharomyces cerevisiae. The inoculation ratios of two yeasts ranged from 0.1 to 10 and fermentations with pure S. cerevisiae were utilized as control. Esterase activities that expressed as C2-C8 chain substrate specificity were surveyed during mixed fermentation. Finally, wine aroma was analyzed via GC-MS and a trained sensory panel. The results revealed that C2-C8 esterase activities were superior during mixed fermentation to the control. Mixed fermentations significantly increased the contents of acetates, ethyl esters, fatty acids, and numerous other fermentative volatiles; particularly those of medium-chain fatty acids and their corresponding esters, with an increased inoculation ratio of the isolate. Extracellular enzyme treatment highly improved the release of varietal aroma compounds, such as terpenols, C13-norisoprenoids, and C6 compounds. Sensory analysis indicated that the risk of negative earth odor emerged in the wine characterized by strong sweet and acid fruit trait. Therefore, mixed fermentations at yeasts inoculation ratios between 1:4 and 4:1 may provide better fermentation strategies for appropriate wine aroma enhancement.

Ma D et al (2017) LWT – Food Science and Technology 86:361-370

 

Strains of the Lactobacillus casei group show diverse abilities for the production of flavor compounds in 2 model systems (research)

Cheese flavor development is directly connected to the metabolic activity of microorganisms used during its manufacture, and the selection of metabolically diverse strains represents a potential tool for the production of cheese with novel and distinct flavor characteristics. Strains of Lactobacillus have been proven to promote the development of important cheese flavor compounds. As cheese production and ripening are long-lasting and expensive, model systems have been developed with the purpose of rapidly screening lactic acid bacteria for their flavor potential. The biodiversity of 10 strains of the Lactobacillus casei group was evaluated in 2 model systems and their volatile profiles were determined by gas chromatography-mass spectrometry. In model system 1, which represented a mixture of free AA, inoculated cells did not grow. In total, 66 compounds considered as flavor contributors were successfully identified, most of which were aldehydes, acids, and alcohols produced via AA metabolism by selected strains. Three strains (DPC2071, DPC3990, and DPC4206) had the most diverse metabolic capacities in model system 1. In model system 2, which was based on processed cheese curd, inoculated cells increased in numbers over incubation time. A total of 47 compounds were identified, and they originated not only from proteolysis, but also from glycolytic and lipolytic processes. Tested strains produced ketones, acids, and esters. Although strains produced different abundances of volatiles, diversity was less evident in model system 2, and only one strain (DPC4206) was distinguished from the others. Strains identified as the most dissimilar in both of the model systems could be more useful for cheese flavor diversification.

Stefanovic E et al (2017) Journal of Dairy Science 100:6818-6929

 

Physiology, ecology and industrial applications of aroma formation in yeast (review)

Yeast cells are often employed in industrial fermentation processes for their ability to efficiently convert relatively high concentrations of sugars into ethanol and carbon dioxide. Additionally, fermenting yeast cells produce a wide range of other compounds, including various higher alcohols, carbonyl compounds, phenolic compounds, fatty acid derivatives and sulfur compounds. Interestingly, many of these secondary metabolites are volatile and have pungent aromas that are often vital for product quality. In this review, we summarize the different biochemical pathways underlying aroma production in yeast as well as the relevance of these compounds for industrial applications and the factors that influence their production during fermentation. Additionally, we discuss the different physiological and ecological roles of aroma-active metabolites, including recent findings that point at their role as signaling molecules and attractants for insect vectors.

Dzialo MC et al (2017) FEMS Microbiology Reviews 41:S95-S128

The Monthly Digest – Aromas and Flavours July & August 2017

Aromas and flavours
R & D abstracts – July & August 2017
Fermentation characteristics and aromatic profile of plum wines produced with indigenous microbiota and pure cultures of selected yeast (research)

Plum (Prunus domestica L.) is one of the most often grown fruit species, which is widespread all over the world. The processing potential of this fruit is not exploited enough. Fruit wines became very popular nowadays because of their nutritional and health-promoting values. Plums are fruit that can give wine with intensive red color and characteristic flavor, which can be compared with the best grape wines. Obtained results would contribute to global acceptance of wine as functional food. An important advantage of fruit wines (concretely plum wine) compared to traditional grape wine is lower alcohol content. Also, plum fruits losses in refrigeration industry could be avoided due to longer shelf life of this fermented beverage.
The aim of this study was to assess and compare fermentation characteristics and aromatic profile of plum wines produced with indigenous microbiota and pure cultures of different selected yeast. Experiments were carried out with plum (Prunus domestica L.) varieties of different fruit ripening times (Čačanska rana, Čačanska lepotica, and Požegača). Wine fermentations were conducted by the activity of indigenous microbiota, commercially available Saccharomyces cerevisiae and Saccharomyces bayanus yeast strains and joint activity of Schizosaccharomyces pombe and S. cerevisiae (sequential inoculation). Statistically significant differences in fermentative characteristics and the content of certain volatile compounds were observed as a result of metabolic activity of various indigenous and/or selected yeasts during fermentation of plum pomace. Minimal duration of fermentation (4 to 5 d) and fastest ethanol production rate (from 12.3 to 15.5 g/L/d) were the characteristics of the studied S. cerevisiae strains. Isobutanol, 3-methyl-1-butanol, 1-heptanol, and 1-octanol were the most prevalent higher alcohols in the tested plum wine samples. The predominant ester in plum wines was ethyl acetate, ethyl lactate, amyl acetate, isoamyl acetate, and ethyl palmitate, esters responsible for the floral and fruity olfactory tones, were also present in large amounts. Also, the use of S. cerevisiae strains resulted in the production of plum wines with better sensory characteristics than ones produced with other investigated yeasts. Obtained results are significant since there is limited data on the compounds responsible for the unique flavor of plum wine, as well as on the impact of different yeast starter cultures application on the overall quality of fruit wines.

Miljic U et al (2017) Journal of Food Science 82:1443-1450

 

Agrowaste to vanillin conversion by a natural Pediococcus acidilactici strain BD16 (research)

Owing to its flavoring, antimicrobial, antioxidant and anticarcinogenic nature, vanillin is widely used in foods, beverages, perfumes and pharmaceutical products. Ferulic acid (FA) is an important precursor of vanillin which is abundant in cereals like maize, rice and wheat and sugar beet. A major drawback of microbial vanillin production from FA is the degradation and biotransformation of toxic vanillin to other phenolic derivatives. The present study is undertaken to explore microbial vanillin production from FA precursor rice bran by employing vanillin-resistant Pediococcus acidilactici BD16, a natural lactic acid bacteria isolate. Extracellular, intracellular and cellular vanillin dehydrogenase activity was found least, which was minimized vanillin degradation, and the strain resists more than 5 g L−1 vanillin in the medium. A metabolomics approach was followed for the detection of FA, vanillin and other metabolites generated during fermentation of rice bran medium. A metabolic pathway was also predicted for vanillin biosynthesis. Approximately 1.06 g L−1 of crude vanillin was recovered from rice-bran-containing medium and this further offers scope for the industrial utilization of the organism and its genetic manipulation to enhance production of biovanillin.

Chakraborty D et al (2017) Environmental Technology 38:1823-1834

 

Improvement of aroma and shelf-life of non-alcoholic beverages through cyclodextrins-limonene inclusion complexes (research)

Limonene is a monoterpene flavor compound found in several beverages. However, it easily degrades by oxidation reactions at acidic environment contributing to an undesirable off-flavor. Encapsulation technologies can protect compounds from degradation. This work focuses on the effect of using complexes of limonene with
α-, β-, and γ- and HP-β-cyclodextrins in non-alcoholic beverages to improve flavor and shelf-life stability due to the chemical structure of cyclodextrins. Spray-drying technology was applied to prepare different cyclodextrin/limonene forms, from which the most promising was selected and further applied in simulated lemon juice beverages. Different drying process conditions were tested, namely feed temperature (120, 160, and 180 °C) and setting of prior incubation (temperature, room and 50 °C; time, 0.17 and 24 h). An inlet temperature of 160 °C favored the encapsulation of limonene into resulting nano/microparticles. Moreover, incubation for 24 h enhanced limonene retention for all complexes, especially for β-cyclodextrin/limonene complexes, which achieved 66% of encapsulation efficiency and a 6.25 w/w of limonene load. The β-cyclodextrin/limonene particles which enabled higher load (160 °C, 24 h) presented particle size ranging between 1 and 3 μm and were chosen to undergo an accelerated aging process in a lemon juice
beverage model. This study revealed that the limonene content decreased over time for model and supplemented juice, but decreased less when β- cyclodextrin/limonene particles were added. After 10 days, which mimics 9 months of storage, 40% of complexed limonene remained in the model beverage.

Saldanha do Carmo C et al (2017) Food and Bioprocess Technology 10:1297-1309

 

Intracellular metabolite profiling of industrial yeast and the synthesis of flavour compounds in beer (research)

Beer quality is largely guaranteed by a rational ratio of different flavour compounds. In this study, we present intracellular metabolic profiles in the light of lager beer flavour compound synthesis on an industrial scale. A total of 62 intracellular metabolites were identified and quantitatively analysed. Among these, amino acid was identified as the most dominant category of metabolites. We also report gene expression profiling of relevant genes encoding six representing amino acids, including serine, alanine, lysine, valine, leucine and asparagine. Nine genes involved in the amino acid synthesis – ALT1, ALT2, ASN1, ASN2, BAT1, SER2, SHM1, SHM2 and LYA1 displayed significantly higher level of expression at various fermentation stages in an industrial lager fermentation. However, concentrations of the recovered amino acids decreased towards the end of fermentation. Our results suggested that the defined amino acids could be assimilated by the yeast to be utilized for synthesis of aroma-active metabolites at different stages in fermentation.

Yin H et al (2017) Journal of the Institute of Brewing (in press)

 

Great intraspecies diversity of Pichia kudriavzevii in cocoa fermentation highlights the importance of yeast strain selection for flavor modulation of cocoa beans (research)

The use of selected yeasts has recently been proposed as an interesting strategy to improve cocoa bean fermentation and chocolate quality. In this study, a total of 39 cocoa-derived yeast isolates were screened for their capacity to produce volatile aroma compounds in a cocoa pulp simulation medium. The seven highest aroma-producing yeasts were identified by ITS-rRNA gene sequencing as belonging to Pichia kudriavzevii, in spite of exhibiting different metabolic profiles. Repetitive extragenic palindromic (Rep)-PCR genomic fingerprinting approach confirmed this high intraspecies diversity of P. kudriavzevii in cocoa fermentation. Two strains with superior aroma production, namely P. kudriavzevii LPB06 and P. kudriavzevii LPB07, were used in cocoa beans fermentation at laboratory scale. They were able to establish an accelerated fermentation process with efficient yeast growth, sugars consumption and ethanol formation compared to the spontaneous process. The resulting cocoa beans were analyzed by diverse chemical analysis methods, including gas chromatography coupled to mass spectrophotometry (GC-MS), fermentation index and metal and colorimetric analysis. Altogether, the results indicated that inoculated fermentations generated cocoa beans with better color development and richer aroma composition, suggesting that cocoa-associated yeast diversity at strain level can be exploited for flavor modulation of cocoa beans.

Pereira GVM et al (2017) LWT – Food Science and Technology 84:290-297

 

Microbial diversity of traditional kefir grains and their role on kefir aroma (research)

Kefir grains consist of rich bacterial and fungal microflora responsible for the production of this traditional fermented milk beverage with unique flavour properties. Here, a pyrosequencing approach was applied for the identification of microbial flora of four kefir grains collected from different regions of Turkey and the volatile compounds in kefir samples produced with these grains were determined. Lactobacillus kefiranofacienspresented in all grains at important levels and Enterobacter, Acinetobacter, Enterococcus and Pseudomonas spp were observed in traditional kefir grains. The fungal microflora of kefir grains was dominated by yeast species and Dipodascaceaefamily was dominant and Saccharomyces cerevisiae presented in all grains. Other yeast species belonging to Kazachstania, Candida, Issatchenkia and Rhodotorula species were also detected in kefir grains. Volatile compounds of kefir samples were also diverse related to the microbial diversity of kefir grains. This study revealed the rich microflora of Turkish kefir grains and their interactions with the aromatic properties of kefir.

Dertli E and Çon AH (2017) LWT – Food Science and Technology 85A:151-157

The Monthly Digest – Food waste – July & August 2017

Food wastes and by-products
R & D abstracts – July & August 2017
Microbial processing of fruit and vegetable wastes into potential biocommodities: a review

The review focuses on some of the high value-end biocommodities, such as fermented beverages, single-cell proteins, single-cell oils, biocolors, flavors, fragrances, polysaccharides, biopesticides, plant growth regulators, bioethanol, biogas and biohydrogen, developed from the microbial processing of fruit and vegetable wastes. Microbial detoxification of fruit and vegetable processing effluents is briefly described. The advances in genetic engineering of microorganisms for enhanced yield of the above-mentioned biocommodities are elucidated with selected examples. The bottleneck in commercialization, integrated approach for improved production, techno-economic feasibility and real-life uses of some of these biocommodities, as well as research gaps and future directions are discussed.

Panda SK et al (2017) Critical Reviews in Biotechnology (in press)

 

Waste biorefineries: Enabling circular economies in developing countries (review)

This paper aims to examine the potential of waste biorefineries in developing countries as a solution to current waste disposal problems and as facilities to produce fuels, power, heat, and value-added products. The waste in developing countries represents a significant source of biomass, recycled materials, chemicals, energy, and revenue if wisely managed and used as a potential feedstock in various biorefinery technologies such as fermentation, anaerobic digestion (AD), pyrolysis, incineration, and gasification. However, the selection or integration of biorefinery technologies in any developing country should be based on its waste characterization. Waste biorefineries if developed in developing countries could provide energy generation, land savings, new businesses and consequent job creation, savings of landfills costs, GHG emissions reduction, and savings of natural resources of land, soil, and groundwater. The challenges in route to successful implementation of biorefinery concept in the developing countries are also presented using life cycle assessment (LCA) studies.

Nizami AS et al (2017) Bioresource Technology 241:1101-1117

 

Valorization of potato peel: a biorefinery approach (review)

Potato is the fourth main crop consumed worldwide and is an important constituent in the human diet. Consequently, potato is widely used in food-processing industries. However, these industries generate massive amounts of potato peel (PP) as a by-product, which is usually considered a waste, and is discarded. Interestingly, recent research suggests that PP is a valuable source of bioactive compounds, which can be converted into value-added products. In this study, we review the physicochemical composition and valorization of PP. In addition to being used as a dietary fiber or medicine, the value-added products obtained by the fermentation of PP have multiple uses, including their use as adsorbents, biocomposites and packaging materials. These products can also be used in energy production, biopolymer film development, corrosion inhibition and the synthesis of cellulose nanocrystals. The biorefinery approach for PP will increase the value of this waste by producing an array of value-added products and reducing extensive waste generation.

Pathak PD et al (2017) Critical Reviews in Biotechnology (in press)

 

Optimization of cultivation conditions in banana wastes for production of extracellular β-glucosidase by Trichoderma harzianum Rifai efficient for in vitro inhibition of Macrophomina phaseolina (research)

The present study was carried out to optimize the physical and nutritional parameters for cultivation of Trichoderma harzianum Rifai for production of extracellular β-glucosidase, an alternative to chemcial fungicides to control Macrophomina phaseolina, which causes charcoal rot disease in crops. Response surface methodology by the Box–Behnken design (BBD) based on four factors (temperature, carbon sources, inoculum size and pH) was used for optimization of the cultivation conditions to produce β-glucosidase using agro-industrial banana wastes. The highest β-glucosidase activity (1483.27 U/mL) was attained under optimized cultivation conditions: ∼36 ºC and pH 7.3, using carbon source and inoculum size of 10% (w/v) and 5% (w/v), respectively. It is noteworthy that the low deviation values (0.09−0.44%) in the verification experiments (R1, R2 and R3) inferred the generated model was accurate to predict optimal cultivation conditions of T. harzianumRifai. Likewise, the obtained diameters of inhibition zones ranging from 58.00−38.66 mm following treatment with β-glucosidase was found comparable to other in vitro tests using pure T. harzianum isolates and chemical fungicides. Hence, the findings indicated that it was feasible to use β-glucosidase as a greener alternative to chemical fungicides for control of M. phaseolina infection and consequently, for protection of crops against charcoal rot disease.

Khalili E et al (2017) Biotechnology & Biotechnological Equipment (in press)

 

Agrowaste to vanillin conversion by a natural Pediococcus acidilactici strain BD16 (research)

Owing to its flavoring, antimicrobial, antioxidant and anticarcinogenic nature, vanillin is widely used in foods, beverages, perfumes and pharmaceutical products. Ferulic acid (FA) is an important precursor of vanillin which is abundant in cereals like maize, rice and wheat and sugar beet. A major drawback of microbial vanillin production from FA is the degradation and biotransformation of toxic vanillin to other phenolic derivatives. The present study is undertaken to explore microbial vanillin production from FA precursor rice bran by employing vanillin-resistant Pediococcus acidilactici BD16, a natural lactic acid bacteria isolate. Extracellular, intracellular and cellular vanillin dehydrogenase activity was found least, which was minimized vanillin degradation, and the strain resists more than 5 g L−1 vanillin in the medium. A metabolomics approach was followed for the detection of FA, vanillin and other metabolites generated during fermentation of rice bran medium. A metabolic pathway was also predicted for vanillin biosynthesis. Approximately 1.06 g L−1 of crude vanillin was recovered from rice-bran-containing medium and this further offers scope for the industrial utilization of the organism and its genetic manipulation to enhance production of biovanillin.

Chakraborty D et al (2017) Environmental Technology 38:1823-1834

 

Potato peels: A potential food waste for amylase production (research)

In the present study, thermophilic and amylase producing bacterium Bacillus subtilis K-18 (KX881940) was isolated from local environment and identified by 16S rRNA gene sequencing technology. The amylase producing potential was checked by starch hydrolysis test using potato peels as carbon source. Central composite design (CCD) of response surface methodology (RSM) was used to optimize multiple process parameters such as substrate concentration, inoculum size, yeast extract, and pH. The optimized conditions obtained from RSM model were substrate concentration (2%), inoculum size (4%), yeast extract concentration (0.6%), and pH (5) yielding amylase activity of 1394.145 IU/ml after 24 hr of fermentation period at 50 °C. The maximum saccharification by indigenously produced amylase was 32.03% after 24 hr of incubation. The results confirmed that amylase produced by this newly isolated Bacillus subtilis K-18 (KX881940) could be potent strain for industrial process particular for biofuel production. The enzyme produced in this study could be effectively used in hydrolysis of starch to produce sugars which could be widely used for the production of various chemicals such ethanol and other products through fermentation. This enzyme also has potential application in textile industry.

Mushtaq Q et al (2017) Journal of Food Process Engineering 40 (in press)

 

Minimally processed beetroot waste as an alternative source to obtain functional ingredients (research)

Large amounts of waste are generated by the minimally processed vegetables industry, such as those from beetroot processing. The aim of this study was to determine the best method to obtain flour from minimally processed beetroot waste dried at different temperatures, besides producing a colorant from such waste and assessing its stability along 45 days. Beetroot waste dried at 70 °C originates flour with significant antioxidant activity and higher betalain content than flour produced from waste dried at 60 and 80 °C, while chlorination had no impact on the process since microbiological results were consistent for its application. The colorant obtained from beetroot waste showed color stability for 20 days and potential antioxidant activity over the analysis period, thus it can be used as a functional additive to improve nutritional characteristics and appearance of food products. These results are promising since minimally processed beetroot waste can be used as an alternative source of natural and functional ingredients with high antioxidant activity and betalain content.

Porto Dalla Costa A et al (2017) Journal of Food Science and Technology 54:2050-2058

 

Comparison of the anaerobic digestion at the mesophilic and thermophilic temperature regime of organic wastes from the agribusiness (research)

An overall kinetic power law model has been successfully applied to study the anaerobic digestion of agricultural wastes. In this comparative kinetic study feed composition, organic load rate, residence time and process temperature have been systematically varied in an automated semi-continuous fermentation system to obtain the dependency of the rate of degradation as biogas production on the organic load rate and temperature. The results show that the overall reaction order depend only on the Chemical Oxygen Demand (COD) at values between 3.6 and 3.7. The Arrhenius approach shows a shift in the rate determining step between the mesophilic and thermophilic temperature regimes. The activation energy at the temperature insensitive mesophilic regime is very small at 8.9 (kJ/mole), while the activation energy at the temperature sensitive thermophilic regime lies around 117 (kJ/mole).

Almeida Streitwieser D (2017) Bioresource Technology 241:985-982