Efficacy and Mechanism of Lactic Acid Production from Food Waste Fermentation Regulated by Magnesium Ions
The utilization of food waste as a fermentation substrate can effectively reduce the substrate cost of lactic acid production industrialization, and synergistic fermentation with leachate could promote lactic acid production. However, the effect of magnesium ions in leachate on lactic acid production, metabolic processes, and key functional bacterial communities remains unclear. This study investigated the effect of adding magnesium ions on lactic acid fermentation using food waste as substrate. Results showed that the optimal magnesium ion dosage was 750 mg/L, achieving a lactic acid yield of (37.4±0.5) g COD/L and L-lactic acid optical activity of (96.3±0.9)%. Mechanistic studies revealed that magnesium ions accelerated substrate dissolution, significantly enhanced the activities of key hydrolytic enzymes (α-glucosidase, amylase, protease) and L-lactic acid producing enzymes, thereby increasing hydrolysis and lactate production rates. Simultaneously, the relative activity of lactate-consuming enzymes decreased, slowing lactate consumption. At 750 mg/L Mg2+, the relative abundances of Enterococcus and Streptococcus were 65.0% (2.2 times the Blank) and 18.7% (37.8% of the Blank), respectively, with a total of 83.7%, enhancing lactic acid yield and L-lactic acid optical activity. Metabolic pathway prediction and functional gene analysis further indicated that magnesium ions increased the relative abundance of carbohydrate metabolism pathways and genes encoding lactate dehydrogenase. This study provides technical support for food waste resource utilization.