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In the U.S., 30–40% of all food produced ends up as waste. By taking advantage of biological processes this waste nutrients can be converted into value-added 2,3-butanediol (2,3-BDO). However, food waste contains live bacteria and fungi which must first be inactivated, a process typically done with autoclaving under high pressure steam. If contaminants are not removed they can out-compete added industrial microbes for nutrients, resulting in lower yields of bio-products. Unfortunately, sterilization methods such as autoclaving greatly increase production time, and increase energy consumption. This creates a demand for novel microorganisms that can out-compete food waste microbiota by natural means without the need for sterilization of food waste. For this study, several Bacillus licheniformis isolates from Yellowstone National Park were investigated for their potential use in the 2,3-BDO industry. B. licheniformis species are a strain of industrial importance as of late, due to the wide metabolic functions and sustainable growth conditions above 45 °C. Whole genomic sequencing data and biochemical classification of B. licheniformis YNP1-TSU, B. licheniformis YNP2-TSU, and B. licheniformis YNP3-TSU were assessed and revealed a wide assortment of anti-microbial peptides and antibodies as well as catabolic genes for assimilation of glucose, fructose, galactose, xylose, arabinose, mannose, starch and sucrose, and linoleic acid. All three B. licheniformis strains had an optimal growth temperature of 50 °C, and were identified as high 2,3-BDO producers. Each strain YNP1-TSU, YNP2-TSU, and YNP3-TSU yielded 0.44 g/g, 0.45 g/g, and 0.43 g/g from mixed sugars found in non-sterilized food waste, respectively.

Converting food waste into butanol via acetone, butanol, and ethanol (ABE) fermentation provides the potential to recover energy and value-added chemicals from food waste. However, the high variability of food waste compositions has hindered the consistency and predictability of butanol production, impeding the development of a robust industrial fermentation process. This study characterized the compositional variation of collected food wastes and determined correlations between food waste compositional attributes and butanol yields for a better prediction of food waste fermentation with Clostridium. The total sugar, starch, fiber, crude protein, fat and ash contents (on dry basis) in the food waste samples were in a range of 0.5–53.5%, 0–25.2%, 0.6–26.9%, 5.5–21.5%, 0.1–37.9%, and 1.4–13.7%, respectively. The high variability of food waste composition resulted in a wide range (3.5–11.5 g/L) of butanol concentrations with an average of 8.2 g/L. Pearson’s correlation analysis revealed that the butanol concentrations were strongly and positively correlated with equivalent glucose and starch contents in food waste, strongly and negatively correlated with fiber content, and weakly correlated with total sugar, protein, fat, and ash contents. The regression models constructed based on equivalent glucose and fiber contents reasonably predicted the butanol concentration, with the R2 of 0.80. Our study investigated the variability of food waste composition and, for the first time, unveiled relationships between food waste compositional attributes and fermentation yields, contributing to a greater understanding of food waste fermentation, which, in turn, assists in developing new strategies for increased consistency and predictability of food waste fermentation.

The decreasing supply of fossil fuels and increasing environmental concern of food waste disposal have raised interests in food waste conversation to biofuels such as butanol. Apple pomace, a food processing waste rich in carbohydrates, is a good feedstock for butanol production. The goal of this study is to present and evaluate a process to thoroughly convert apple pomace water soluble sugars (WSS) and hydrolyzed sugars from structural carbohydrates to acetone-butanol-ethanol (ABE) by fermentation. WSS was extracted from apple pomace by hot water. The solid residue was pretreated with acid or alkali followed by enzymatic hydrolysis to obtain acid hydrolyzed sugars (ACHS) or alkali hydrolyzed sugars (ALHS). Finally, WSS, ACHS, ALHS, WSS + ACHS, and WSS + ALHS were used as substrates to produce ABE by Clostridium beijerinckii P260, respectively. Acid and alkali pretreated apple pomace showed significantly (p < 0.05) higher glucose yield after cellulase hydrolysis compared with that of unpretreated apple pomace. Addition of pectinase increased hydrolyzed glucose yield by 27.9%, 26.9%, and 33.0% for acid pretreated sample, alkali pretreated sample, and unpretreated sample, respectively. Fermentation results revealed that inhibitors generated during pretreatment could negatively affect the ABE fermentation rate and titers; however, this negative effect could be alleviated by mixing the hydrolyzed sugars with water soluble sugars. A total of 202.8, 42.1, 41.4, 260.1, and 262.2 g of ABE was produced from each kg of dry apple pomace using WSS, ACHS, ALHS, WSS + ACHS, and WSS + ALHS as the substrates, respectively, based on the mass balance. USDA AFRI Foundational Program [2018-67021-27895]; Virginia Agriculture Experiment Station; Hatch Program of the National Institute of Food and Agriculture (NIFA), USDA This work was supported by the USDA AFRI Foundational Program (grant number 2018-67021-27895) and the Virginia Agriculture Experiment Station and the Hatch Program of the National Institute of Food and Agriculture (NIFA), USDA. Public domain – authored by a U.S. government employee

Conversion of food waste into 2,3-butanediol (2,3-BDO) via microbial fermentation provides a promising way to reduce waste disposal to landfills and produce sustainable chemicals. However, sterilization of food waste, an energy- and capital-costly process, is generally required before fermentation to avoid any contamination, which reduces the energy net output and economic feasibility of food waste fermentation. In this study, we investigated the non-sterile fermentation of food waste to produce 2,3-BDO using a newly isolated thermophilic and alkaliphilic B. licheniformis YNP5-TSU. Three unitary food waste samples (i.e., pepper, pineapple, cabbage wastes) and one miscellaneous food waste mixture were respectively inoculated with B. licheniformis YNP5-TSU under non-sterile conditions. At 50 °C and an initial pH of 9.0, B. licheniformis YNP5-TSU was able to consume all sugars in food waste and produce 5.2, 5.9, 5.9 and 4.3 g/L of 2,3-BDO within 24 h from pepper, pineapple, cabbage and miscellaneous wastes, respectively, corresponding to a yield of 0.40, 0.38, 0.41 and 0.41 g 2,3-BDO/g sugar. These 2,3-BDO concentrations and yields from the non-sterile fermentations were comparable to those from the traditional sterile fermentations, which produced 4.0–6.8 g/L of 2,3-BDO with yields of 0.31–0.48 g 2,3-BDO/g sugar. Moreover, B. licheniformis was able to ferment various food wastes (pepper, pineapple and miscellaneous wastes) without any external nutrient addition and produce similar 2,3-BDO quantities. The non-sterile fermentation of food waste using novel thermophilic and alkaliphilic B. licheniformis YNP5-TSU provides a robust and energy-efficient approach to convert food waste to high-value chemicals.

Background Plant-derived wastes from agriculture, processing, distribution, and retail are generated in large quantities. The majority of the wastes are underutilized and may cause severe environmental problems if not properly handled. The plant-derived wastes are usually rich in lignocellulose and other valuable compounds including protein, fat, sugar, and phytochemicals. Valorization of these compounds in food waste not only reduces environmental concerns but also improves sustainability and economic competitiveness of agro-food industries. Scope and approach This review paper first discussed different phases of the biorefinery concepts and their associated applications, and then introduced recent advances in the integrated processing of plant-derived waste for producing various value-added products. Finally, techno-economic, environmental, and social assessments along with relevant policies were introduced and discussed. Key findings and conclusions During the past ten years, research attentions focused on integrated utilization of plant-derived waste to produce various products have flourished. Compared to production of a single component for food waste valorization, integrated processing of food waste via a combination of different novel technologies to produce multiple products based on a biorefinery concept has significant advantages, including full utilization of feedstocks, minimization of waste generation during processing, synergy effects of different technologies, and diversification of the revenues by covering multiple markets. With the rationale design of biorefinery processes, underutilized plant-based wastes can be valuable resources for the sustainable production of food, chemicals, and biofuels. However, detailed economic, environmental, and social analyses for the biorefinery process are still needed in the future.

Background Waste is currently a major problem in the world, both in the developing and the developed countries. Efficient utilization of food waste for fuel and chemical production can positively influence both the energy and environmental sustainability. This study investigated using food waste to produce acetone, butanol, and ethanol (ABE) by Clostridium beijerinckii P260. Results In control fermentation, 40.5 g/L of glucose (initial glucose 56.7 g/L) was used to produce 14.2 g/L of ABE with a fermentation productivity and a yield of 0.22 g/L/h and 0.35 g/g, respectively. In a similar fermentation 81 g/L of food waste (containing equivalent glucose of 60.1 g/L) was used as substrate, and the culture produced 18.9 g/L ABE with a high ABE productivity of 0.46 g/L/h and a yield of 0.38 g/g. Fermentation of food waste at higher concentrations (129, 181 and 228 g/L) did not remarkably increase ABE production but resulted in high residual glucose due to the culture butanol inhibition. An integrated vacuum stripping system was designed and applied to recover butanol from the fermentation broth simultaneously to relieve the culture butanol inhibition, thereby allowing the fermentation of food waste at high concentrations. ABE fermentation integrated with vacuum stripping successfully recovered the ABE from the fermentation broth and controlled the ABE concentrations below 10 g/L during fermentation when 129 g/L food waste was used. The ABE productivity with vacuum fermentation was 0.49 g/L/h, which was 109 % higher than the control fermentation (glucose based). More importantly, ABE vacuum recovery and fermentation allowed near-complete utilization of the sugars (~98 %) in the broth. Conclusions In these studies it was demonstrated that food waste is a superior feedstock for producing butanol using Clostridium beijerinckii. Compared to costly glucose, ABE fermentation of food waste has several advantages including lower feedstock cost, higher productivity, and less residual sugars.

Ethanol production from food wastes does not only solve environmental issues but also provides renewable biofuels. This study investigated the feasibility of producing ethanol from food wastes at high solids content (35%, w/w). A vacuum recovery system was developed and applied to remove ethanol from fermentation broth to reduce yeast ethanol inhibition. A high concentration of ethanol (144 g/L) was produced by the conventional fermentation of food waste without a vacuum recovery system. When the vacuum recovery is applied to the fermentation process, the ethanol concentration in the fermentation broth was controlled below 100 g/L, thus reducing yeast ethanol inhibition. At the end of the conventional fermentation, the residual glucose in the fermentation broth was 5.7 g/L, indicating incomplete utilization of glucose, while the vacuum fermentation allowed for complete utilization of glucose. The ethanol yield for the vacuum fermentation was found to be 358 g/kg of food waste (dry basis), higher than that for the conventional fermentation at 327 g/kg of food waste (dry basis).