PRODUCTION OF LACTIC-ACID FROM LIGNOCELLULOSE IN A SINGLE-STAGE OF HYDROLYSIS AND FERMENTATION

Samples of a model lignocellulosic substrate (wood subjected to treatm ents of delignification and swelling) were hydrolyzed and fermented in a single stage to obtain lactic acid. The hydrolysis stage was carrie d out using commercial cellulases with or without addition of fresh ce llobiase, and Lactobacillus delbrueckii NRRL B-445 was used for conver ting both glucose and cellobiose into lactic acid. Assays were perform ed starting the hydrolysis and fermentation stages at the same time (S imultaneous Saccharification and Fermentation, SSF) or inoculating hyd rolysis media partially saccharified (Combined Hydrolysis and Fermenta tion, CHF). Both glucose and cellobiose were rapidly depleted by micro organisms, showing a kinetic pattern governed by the hydrolysis stage. The effect of selected operational variables (enzyme loading, substra te concentration and duration of the process) was explored. Under the best conditions assayed, lactic acid concentrations in the vicinity of 30 g/L were reached in experiments lasting 40-60 hours.