A Novel Strategy to Enhance High Optically Active L-lactate Production from Food Waste Upgrading by Landfill Leachate

Large amounts of food waste (FW) are generated annually, which need to be treated safely and environmentally. The anaerobic fermentation of FW for lactic acid (LA) production is promising due to the widespread application of LA in pharmaceutical, food, textile, and chemical industries. However, the product to LA is not easily controlled during FW fermentation due to competition and inhibition. In this study, we adopted high-strength landfill leachate to regulate FW fermentation for high optically active L-lactate production. In particular, the LA yield was significantly increased at a ratio of 18:1 between FW and inoculated waste activated sludge, and the addition of leachate (calculated by NH4+-N = 270 mg/L) resulted in a maximum L-LA of 44.6 g COD/L, which is 1.84 times higher than the control (24.1 g COD/L), Meanwhile, an improved optical activity (OA) of L-LA was also observed (92.8% vs.74.6% of the control). The effect of leachate addition on fermentation pathways, including solubilization, hydrolysis, acidification, and lactate dehydrogenase was also investigated. Genera Streptococcus and enterococcus, two L-LA-producing bacteria, were the most abundant bacteria in the reactor, contributing 32.2% and 35.9%, respectively. This study provides a novel way to enhance the active L-lactate production from FW by landfill leachate.