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

Eight Lactobacillus species were screened for production of lactic aci d from acid-hydrolyzed municipal solid waste (AHMSW). Screening criter ia included carbohydrate utilization, lactic acid production, and the yield of lactic acid produced in modified Elliker broth and in MSW hyd rolyzate. Lactobacillus pentosus B-227 metabolized the most carbohydra te (62%) and produced the highest concentration of lactic acid in AHMS W (21.2 mg/mL) containing 41.3 mg/mL carbohydrate. Fermentation parame ters 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% ca lcium carbonate buffer, L. pentosus B-227 produced 65 mg/mL lactic aci d from 100.6 mg/mL of carbohydrates in MSW hydrolyzate, an 87% yield b ased on carbohydrate utilization.