Production of L-lactic acid from corncob.

The optimum temperature, initial pH, amount of added enzyme and substrate (corncob) for the hydrolysis of corncob by Acremonium cellulase were 35 degrees C, 4.5, 10 u/g-corncob and 100 g/l, respectively. Under the optimum conditions, more than 55 g/l of reducing sugars were hydrolyzed from 100 g/l of corncob to 34 g/l of glucose and 12 g/l of xylose based on dried corncob. More than 25 g/l of L-lactic acid was produced from this enzymatic hydrolyzate and less than 5 g/l of xylose remained in the 3-l airlift bioreactor. The production of L-lactic acid by simultaneous saccharification and fermentation (SSF) was also carried out in the 3-l airlift bioreactor using Acremonium thermophilus (cellulose-producer) and Rhizopus sp. MK-96-1196 (lactic acid-producer). More than 24 g/l of L-lactic acid was produced from 100 g/l of untreated raw corncob.