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Poster Presentation 3-45
Repeated Batch Production of Lactic Acid by Enterococcus faecalis RKY1
Hurok Oh, Young-Jung Wee, Jong-Sun Yun and Hwa-Won Ryu
Faculty of Chemical Engineering and Institute of Bioindustrial Technology Chonnam National University Gwangju 500-757 Korea
Telephone: +82-62-530-1842; Fax: +82-62-530-1849; E-mail: hwryu@chonnam.ac.kr
Lactic acid has a wide range of applications in various fields of industry as food additives, preservatives, pH regulators, etc. Furthermore, much attention has recently been paid to lactic acid as a monomer for biodegradable plastic. Of the two methods of producing lactic acid, fermentation is desirable compared to chemical synthesis due to its environmental friendliness and selectable production of enantiomer. There are, however, two major problems that make biological production of lactic acid economically impractical: the fastidious nutrient requirement of lactic acid bacteria and the end product inhibition caused by accumulated lactic acid. Particularly, the cost of the nitrogen source is over 30% of the total production cost. Therefore, this study on inexpensive and effective nutritional source development and cell-reuse fermentation focused primarily on increasing biomass concentration and volumetric productivity of lactic acid to develop an economical process.
In this study, we investigated repeated batch operation using hollow fiber for the purpose of the reuse of biomass and the reduction of yeast extract dosage simultaneously. When 100 g-glucose/L and 4 g-yeast extract/L were added in the media, the lactic acid productivities of individual batch operations were in the range of 6.15-6.33 g /L/hr. During the subsequent ten repeated batch operation, 93% of overall yield (g-LA produced/g-Glucose supplied) was obtained. Therefore a very stable and consistent fermentation profile was maintained with reduced yeast extract dosage for multiple repeated batch operations.
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