원문정보
초록
영어
Bio-based chemical production, as a part of White Biotechnology, are growing rapidly worldwide,
due to current increase of petroleum cost and demanding concerns to environments. Despite the
merits of lignocellulosic biomass serving as a feedstock for the biological production of chemicals (lactic acid and/or ethanol), commercialization has not been realized because of low yield and high processing costs. Higher yield at lower cost can be achieved with cost-efficient conversion of cellulose-to-glucose and complete utilization of all carbohydrates (pentoses and hexoses). Process design involving simultaneous enzymatic hydrolysis of cellulose coupled with concurrent fermentation of all carbohydrates to target product has been found to reduce cost by increasing productivity and reducing the cost of enzyme. Lactobacillus brevis and Lactobacillus pentosus JH5XP5 were selected for this process due to a wide range of sugar utilization including lignocellulosic-derived carbohydrates. Moreover, L. pentosus JH5XP5 shown that the ethanol production was more than two-fold higher than lactic acid from glucose, galactose and maltose. Without apparent carbon catabolite repression, both L. brevis and L. pentosus JH5XP5 were found to metabolize simultaneously and completely all fermentable carbohydrates present in a culture medium containing acid pre-processed rice straw hydrolysate. Product formation was not affected by any chemical and physical inhibitors in this mixture. Simultaneous saccharification and mixed sugar fermentations (SSMSF) were performed with 15 FPU (or CBU) / g-substrate of cellulase (Novozyme 188) and cellobiase (Spezyme cp) using acid preprocessed rice straw. Enzyme activities were maintained during the cell growth and lactic acid production of both strains, in the fed-batch operation of SSMSF. During the SSMSF, sugars are utilized concurrently and completely and enzyme activities were maintained maximum without feedback inhibition by glucose and/or cellobiose. As a result, it was shown that SSMSF required half the time and 6.6-fold less enzyme than a corresponding sequential hydrolysis and fermentation (SHF) process to produced same amount of final product.