Effect of acidification pretreatment on two-phase anaerobic digestion of acidified food waste.

[Display omitted] • Acidification pretreatment (AP) enhanced the degradation of lactic acid. • AP accelerated the hydrolysis and acidogenesis of acidified food waste (AFW). • AP promoted the acidogenesis of AFW dominated by butyric acid fermentation. • Biochemical methane potential of AFW was improved by 35.77% through AP. • Enzymatic predictions indicated that AP increased the lactate dehydrogenase activity. Acidified food waste significantly disrupts anaerobic digestion, highlighting the need for effective solutions to mitigate its impact. This study presents a method that utilizes acidified sludge to pretreat acidified food waste, thereby significantly improving the efficiency of hydrolysis and acidogenesis. After acidification pretreatment, hydrolysis efficiency improved from 64.54 % to 96.51 %, while acidogenesis efficiency increased from 34.82 % to 49.95 %. Additionally, the concentration of short-chain fatty acids and hydrogen production in the acidification pretreatment group increased by 45.89 % and 48.67 %, respectively. The pretreatment group exhibited a biochemical methane potential of 512.84 ± 13.73 mL/(g volatile suspended solids), which was 35.77 % higher than that of the control group. Mechanism analysis revealed that the higher abundance of genes associated with lactate dehydrogenase in the acidified sludge facilitated the rapid degradation of lactic acid. Moreover, the abundant Clostridium butyricum in the acidified sludge promoted the targeted conversion of lactic acid and other organic matter into butyric acid within the food waste system. This efficient butyric acid fermentation improved the fermentation environment and provided abundant substrates for methane production. This study introduces a promising bio-based strategy to improve the anaerobic digestion efficiency of acidified food waste. [ABSTRACT FROM AUTHOR]