15A-9 |
A novel extractive fermentation process for L(+)-lactic acid production from corn starch by immobilized cells of Rhizopus oryzae. |
A. TAY, Dept. of Food Science, Purdue Univ., 1160 Food Science Bldg., West Lafayette, IN 47905 and S. T. Yang, Dept. of Chemical Engineering, The Ohio State Univ., 140 W. 19th Ave., Columbus, OH 43210. Lactic acid is a specialty chemical with many industrial applications and food industry utilizes the 85 % of total production. It is known that R. oryzae can produce lactic acid from inexpensive carbon sources such as starch which costs ~$ 0.06 /lb. In addition, R. oryzae can utilize very simple medium compare to commercial lactic acid bacteria, which will simplify and reduce the cost of separation. Extractive fermentation is one of promising downstream process, which has low cost compare to other separation methods. Both reactor productivity and product yield can be improved in extractive fermentation because the removal of the fermentation product (lactic acid) reduced product inhibition and shifted the metabolic pathway to favor lactic acid formation. Extractive fermentation also eliminated the use of alkali in pH control and thus reduced the wastes from fermentation process. The objectives of this study are to develop and demonstrate a novel continuous extractive fermentation for lactic acid by R. oryzae in fibrous bed bioreactor. The spores of R. oryzae were inoculated to the growth medium and the cells were immobilized to cotton fiber. The extraction system was integrated to the fermentation system during the production phase. The lactic acid extracted by organic solvent in hollow fiber membrane extractor and stripped by base in the back extractor. The samples were taken at 4-6 hr time interval from base tank and bioreactor. The extractive fermentation produced lactic acid directly from corn starch with a high product yield (~100% w/w) and high lactic acid concentration (~300 g/L). The results showed that the new fungal fermentation process is advantageous over bacterial fermentations, including high product yield and productivity, simple medium composition and direct utilization of starch.
Session 15A, Biotechnology
|