Using the simultaneous saccharification and fermentation (SSF) technique, pulp mill solid waste cellulose was converted into glucose using cellulase enzyme and glucose into lactic acid using NRRL B445. SSF experiments were conducted at various pH levels, temperatures, and nutrient concentrations, and the lac tic acid yield ranged from 86 to 97%. The depletion of xylose in SSF was further investigated by inoculating NRRL B445 into a xylose-only medium. On prolonged incubation, depletion of xylose with lactic acid production was observed. An experimental procedure with a nonglucose medium was developed to eliminate the lag phase. From xylose fermentation, Lactobacillus delbrueckii yielded 88-92% lactic acid and 2-12% acetic acid.