MEMBRANE-MEDIATED EXTRACTIVE FERMENTATION FOR LACTIC-ACID PRODUCTION FROM CELLULOSIC BIOMASS

Lactic acid production from cellulosic biomass by cellulase and Lactob acillus delbrueckii was studied in a fermenter-extractor employing a m icroporous hollow fiber membrane (MHF). This bioreactor system was ope rated under a fed-batch mode with continuous removal of lactic acid by an in situ extraction. A tertiary amine (Alamine 336) was used as an extractant for lactic acid. The extraction capacity of Alamine 336 is greatly enhanced by addition of alcohol. Long-chain alcohols serve wel l for this purpose since they are less toxic to micro-organism. Additi on of kerosene, a diluent, was necessary to reduce the solvent viscosi ty. A solvent mixture of 20% Alamine 336, 40% oleyl alcohol, and 40% k erosene was found to be most effective in the extraction of lactic aci d. Progressive change of pH from an initial value of 5.0 down to 4.3 h as significantly improved the overall performance of the simultaneous saccharification and extractive fermentation over that of constant pH operation. The change of pH was applied to promote cell growth in the early phase, and extraction in the latter phase.