Production of lipase by high cell density fed-batch culture of Candida cylindracea

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(-1). However, high initial concentrations of oleic acid up to 50 g l(-1) were not inhibitory. The highest extracellular lipase activity obtained in flask culture was 3.0 U ml(-1) after 48 h with 5 g l(-1) 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(-1) and the extracellular lipase activity was 6.3 U ml(-1) 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(-1) when the set point of specific growth rate (Net) 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 fedbatch cultures due to build-up of the oleic acid oversupplied. The highest extracellular lipase activity was 23.7 U ml(-1) when mu(set) was 0.02 h(-1), while the highest lipase roductivity was 0.31 U ml(-1) h(-1) at mu(set) of 0.08 h(-1).