Monday, April 30, 2007

Production of lactic acid by continuous culture of Lactobacillus sp. RKY2 from glucose and wood hydrolyzate

Jae-Hoon Jeong, Young-Jung Wee, and Hwa-Won Ryu. School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, South Korea

Lactic acid is considered one of the most useful chemicals and widely used in food, textile, pharmaceutical, and chemical industries. The demand for lactic acid derived from biotechnological route has significantly increased due to its application as a monomer to the production of poly(lactic acid) polymer, a biodegradable and sustainable material. However, it is necessary to reduce the production costs for economical production of lactic acid. For this objective, continuous production of lactic acid using wood hydrolyzate and corn steep liquor as main nutrient sources was investigated. In addition, cell-recycle system was combined with continuous production of lactic acid to increase volumetric productivity. The medium composition for Lactobacillus sp. RKY2 was glucose 50-100 g/L or wood hydrolyzate containing glucose 50-75 g/L, CSL 30 g/L, yeast extract 1.5 g/L, (NH4)2HPO4 2 g/L, and MnSO4 0.1 g/L. When the wood hydrolyzate containing 50 g/L and 75 g/L of glucose was used as carbon source, the maximum volumetric productivities of lactic acid were enhanced to 6.3 g/L·h and 6.7 g/L·h, respectively, through cell-recycle continuous process. In this study, wood hydrolyzate and corn steep liquor were found to be quite available for continuous production of lactic acid, and the process could be further improved by introducing cell-recycle systems.