BIOCONVERSION OF MUNICIPAL SOLID-WASTE TO LACTIC-ACID BY LACTOBACILLUS SPECIES

Eight Lactobacillus species were screened for production of lactic acid from acid-hydrolyzed municipal solid waste (AHMSW). Screening criteria included carbohydrate utilization, lactic acid production, and the yield of lactic acid produced in modified Elliker broth and in MSW hydrolyzate. Lactobacillus pentosus B-227 metabolized the most carbohydrate (62%) and produced the highest concentration of lactic acid in AHMSW (21.2 mg/mL) containing 41.3 mg/mL carbohydrate. Fermentation parameters for the bioconversion of carbohydrates in MSW to lactic acid also were evaluated. Under optimum conditions, consisting of an initial pH of 7.6, 32 degrees C, static fermentation, 1% v/v inoculum, and 5% calcium carbonate buffer, L. pentosus B-227 produced 65 mg/mL lactic acid from 100.6 mg/mL of carbohydrates in MSW hydrolyzate, an 87% yield based on carbohydrate utilization.