The degradation of allyl isothiocyanate and its impact on methane production from anaerobic co-digestion of kitchen waste and waste activated sludge

Insights into the Occurrence, Fate, Impacts, and Control of Food Additives in Food Waste Anaerobic Digestion: A Review

“…Increased AITC decreased microbial diversity but had no discernible effect on the microbial structure . Firmicutes and Actinobacteriot were the dominant bacteria at the phylum level, with or without the addition of AITC, while Euryarchaeota was the dominant Archaea phylum.…”

“…Another possibility is that the HS anions formed by OCS are joined to the carbon atom of AITC to form allyl dithiocarbamate, which is then degraded in neutral media to carbon disulfide and allylamine. Through anaerobic digestion, these metabolites eventually produce methane . It is worth noting that Wang et al reported that MSG was also eventually degraded to methane in anaerobic digestion systems.…”

“…(B) Inhibition mechanisms of food additives on anaerobic digestion, which mainly include leaching of intracellular contents and lysis of cells, impeding ATP production and inactivation of key enzymes. The mark ① means salt, the mark ② capsaicin, the mark ③ allicin, and the mark ④ AITC. ,,,, …”

“…AITC can inactivate acetate kinase (AK) by breaking cysteine bonds or interacting with free amino and thiol groups, and AITC inhibits AK enzyme activity more severely than other enzymes, which may explain why it inhibits acetotrophic methanogenesis more effectively. 29 AITC possesses an electrophilic potential and has the ability to modify the electron acceptor, polar, and nonpolar components of the cell membrane, hence increasing the electron acceptor capacity of the cell. 75 AITC might also impair the integrity of the cytoplasmic membrane and decrease the negative surface charge by altering the hydrophobic characteristics of outer membrane lipopolysaccharides, ultimately resulting in cell inactivation and/or death.…”

“…As a sustainable technology, anaerobic digestion can effectively reduce the volume of food waste, stabilize organics, and eliminate pathogens . In addition, anaerobic digestion is considered to have the potential to reduce the risk of transmission of antibiotic resistance genes (ARGs) in food waste. , However, anaerobic digestion of food waste easily encounters technical issues such as the accumulation of volatile fatty acids (VFAs) and ammonia inhibition owing to the unbalanced C/N ratio and trace metal deficiency of food waste. − Among the four stages of anaerobic digestion (i.e., hydrolysis, acidogenesis, acetogenesis, and methanogenesis), hydrolysis is the main rate-limiting step while methanogensis is the decisive step that is directly related to final methane production and sensitive to adverse factors such as temperature, pH, and toxicants. − Researchers have devised a number of physical, chemical, and biological techniques to accelerate hydrolysis and optimize the methanogensis to increase the production of methane from food waste. − However, most of them mainly focused on improving the biotransformations of proteins, polysaccharide, and lipids in food waste. − None of the previous reviews addressed the interaction between anaerobic digestion and food additives that often accumulate in large quantities in food waste, mainly including salt, capsaicin, allicin, allyl isothiocyanate (AITC), monosodium glutamate (MSG), and nonnutritive sweeteners (NNS). − This situation hides the details of what is happening in the anaerobic digestion of food waste in the real world, which is not conducive to the deep control and regulation of the anaerobic digestion system.…”