|Kim, Beom Soo|
Submitted to: Bioprocess and Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2006
Publication Date: 5/15/2006
Citation: Kim, B., Hou, C.T. 2006. Production of lipase by high cell density fed-batch culture of Candida cylindracea. Bioprocess and Biosystems Engineering. 29:59-64. Interpretive Summary: Vegetable oils such as soybean oil and corn oil are cheap raw materials. Various value-added oxygenated fatty acids have been produced from unsaturated fatty acids such as oleic and linoleic acid by biotransformation. Lipase from the non-pathogenic yeast Candida rugosa is another important value-added industrial product with wide applications that can be produced from surplus vegetable oils. High cell density is often necessary for high yield and productivity of the desired product. In this study, we carried out fed-batch cultures of C. rugosa by controlling the nutrient feeding to obtain high cell density and thus high lipase activity. By fed-batch culture with low set point of growth rate at 0.02 h-1, highest lipase activity was obtained by preventing the build-up of oleic acid in culture broth during the later part of fed-batch culture. Cell concentration could be increased to a high density of 90 g/L without supplying pure oxygen.
Technical Abstract: Candida cylindracea NRRL Y-17506 was grown to produce extracellular lipase from oleic acid as a carbon source. Through flask cultures, it was found that the optimum initial oleic acid concentration for cell growth was 20 g/L. However, high initial concentrations of oleic acid up to 50 g/L were not inhibitory. The highest extracellular lipase activity obtained in flask culture was 3.0 U/ml after 48 h with 5 g/L of initial oleic acid concentration. Fed-batch cultures (intermittent and stepwise feeding) were carried out to improve cell concentration and lipase activity. For the intermittent feeding fed-batch culture, the final cell concentration was 52 g/L and the extracellular lipase activity was 6.3 U/ml at 138.5 h. Stepwise feeding fed-batch cultures were carried out to simulate an exponential feeding and to investigate the effects of specific growth rate (0.02, 0.04 and 0.08 h-1) on cell growth and lipase production. The highest final cell concentration obtained was 90 g/L when the set point of specific growth rate (micro-set) was 0.02 h-1. High specific growth rate (0.04 and 0.08 h-1) decreased extracellular lipase production in the later part of fed-batch cultures due to build-up of the oleic acid oversupplied. The highest extracellular lipase activity was 23.7 U/ml when micro-set was 0.02 h-1, while the highest lipase productivity was 0.31 U/ml/h at micro-set of 0.08 h-1.