Distribution of extracellular amino acids and their potential functions in microbial cross-feeding in anaerobic digestion systems

Du, Jin; Yin, Qidong; Zhou, Xingzhao; Guo, Qiannan; Wu, Guangxue

doi:10.1016/j.biortech.2022.127535

Cited by 11 publications

(7 citation statements)

References 42 publications

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“…The degradation of proteins in the food waste led to the production of a higher concentration of glutamate, and seemingly it was difficult to be degraded by microbes in the group, thus leading to its accumulation. Notably, Glu and Ala were not only key cytoarchitectural components and central metabolites but could be biosynthesised at a relatively low energy cost [24,31]. In addition, threonine declined from the initial 0.38 g/L to 0.013 g/L, and cysteine was quickly degraded and utilised, while valine, iso-leucine, leucine, and other amino acids with low initial content were quickly consumed and completely degraded.…”

Section: Effect Of Ph On Hydrolysis and Acid Productionmentioning

confidence: 99%

“…In the reactor, an amino acid acts as an electron donor, while another amino acid acts as an electron acceptor, offering cells approximately 0.5 moles of ATP per mole of amino acid transformed during the reaction [30]; (2) individual amino acids can also be fermented in processes that require the presence of hydrogen utilising bacteria. Commonly, the degradation products of these amino acids under anaerobic conditions are organic compounds (short-chain and branchedchain organic acids), ammonia, carbon dioxide, and small amounts of hydrogen and sulfur compounds [24,42]. However, certain amino acids can also be degraded during anaerobic fermentation to generate lactic acid.…”

Section: Effects Of Adding Different Amino Acids On Food Waste Fermen...mentioning

confidence: 99%

“…Fermentation 2024, 10, x FOR PEER REVIEW 9 of 16 conditions are organic compounds (short-chain and branched-chain organic acids), ammonia, carbon dioxide, and small amounts of hydrogen and sulfur compounds [24,42]. However, certain amino acids can also be degraded during anaerobic fermentation to generate lactic acid.…”

Section: Effects Of Adding Different Amino Acids On Food Waste Fermen...mentioning

confidence: 99%

“…During the AD process, organic matter such as food waste is commonly degraded, and amino acids (AAs) are the main intermediates of protein degradation. Reportedly, amino acids are also nutrients required by microorganisms, and many of the AAs cannot be synthesised during AD, and a number of the AAs must be harvested from the environment [24]. Therefore, it is important to supply certain amino acids that have important biological functions in anaerobic fermentation.…”

Section: Introductionmentioning

confidence: 99%

“…Certain D-AAs such as D-leucine and D-methionine can act as signalling molecules to regulate cell wall biogenesis, biofilm integrity, and spore germination, trigger microbial biofilm disintegration at low concentrations to regulate the distribution of bacterial populations, and influence the surrounding ecosystem [25,27,28]. To date, the focus on free amino acids in anaerobic digestion is mainly on the biodegradability of amino acids, which are commonly produced from substrates such as gelatin, sewage sludge, and food waste during fermentation [24,[29][30][31]. Furthermore, some amino acids have been reported to play a positive role in enhancing the anaerobic digestion process.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism and Effect of Amino Acids on Lactic Acid Production in Acidic Fermentation of Food Waste

Zhou,

Zhang,

Wang

et al. 2024

Fermentation

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Amino acids, particularly the ones that cannot be synthesised during fermentation, are reportedly to be key nutrients for anaerobic fermentation processes, and some of the acids are also intermediate products of anaerobic fermentation of protein-rich waste. To date, particularly, there is a lack of research on the effects of some amino acids, such as cysteine, glycine, aspartic acid, and valine, on lactic production from the fermentation of food waste and also the mechanisms involved in the process. Thus, this study investigated the effects of the four different amino acids on lactic acid production during the acidic anaerobic fermentation of food waste. Firstly, batch experiments on synthetic food waste at different pHs (4.0, 5.0, and 6.0) were executed. The results harvested in this study showed that higher LA concentrations and yields could be obtained at pH 5.0 and pH 6.0, compared with those at pH 4.0. The yield of lactic acid was slightly lower at pH 5.0 than at pH 6.0. Furthermore, caustic consumption at pH 5.0 was much lower. Therefore, we conducted batch experiments with additions of different amino acids (cysteine, glycine, aspartic acid, and valine) under pH 5.0. The additions of the four different amino acids showed different or even opposite influences on LA production. Glycine and aspartic acids presented no noticeable effects on lactic acid production, but cysteine evidently enhanced the lactic acid yield of food waste by 13%. Cysteine addition increased α-glucosidase activity and hydrolysis rate and simultaneously enhanced the abundance of Lactobacillus at the acidification stage as well as lactate dehydrogenase, which also all favoured lactic acid production. However, the addition of valine evidently reduced lactic acid yield by 18%, and the results implied that valine seemingly inhibited the conversion of carbohydrate. In addition, the low abundance of Lactobacillus was observed in the tests with valine, which appeared to be detrimental to lactic acid production. Overall, this study provides a novel insight into the regulation of lactic acid production from anaerobic fermentation of food waste by adding amino acids under acidic fermentation conditions.

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Section: Effect Of Ph On Hydrolysis and Acid Productionmentioning

confidence: 99%