Enhancing lactic acid production from food waste through cavitation pretreatment and biocatalyst amendment – A comparative study

Abstract

Food waste (FW) fermentation into valuable lactic acid (LA) aligns with circular economy goals, but is constrained by low substrate conversion efficiency and mixed product spectrum. This study evaluated the effects of acoustic cavitation pretreatment, biocatalyst (yeast extract) supplementation, and their combination on the targeted LA production. Acoustic cavitation (20 kHz and 450 W/L for 30 min) enhanced FW solubilization by 9.6-fold and increased LA yield to 0.40 g COD/g VSS. With biocatalyst amendment, the hydrolysis phase was improved, and the highest LA yield reached 0.34 g COD/g VSS. When combined, the yield slightly increased to 0.42 g COD/g VSS, exhibiting only a marginal synergistic effect over the individual treatments. The treatments suppressed volatile fatty acid (VFA) formation and promoted LA accumulation. Microbial community analysis revealed an increased abundance of lactic acid bacteria, particularly Schleiferilactobacillus, Lactiplantibacillus, and Levilactobacillus, with concurrent suppression of VFA-producing bacteria, such as Prevotella and Megasphaera. The findings provide new insights into optimizing chiral LA production from complex waste streams and highlight the potential of integrated bioprocessing strategies.