Intracellular lipase production by Rhizopus chinensis using biomass support particles in a circulating bed fermentor

Abstract

To utilize Rhizopus chinensis cells directly as a catalyst for industrial interesterification of oils and fats, the mass production of acetone-dried cells immobilized in Biomass Support Particles (BSPs) which show high intracellular lipase activity was examined using a circulating bed fermentor (CBF). First, the effects of aeration rate and number of BSPs were investigated in batch culture. The results revealed that the aeration rate had a significant influence on the formation of intracellular lipase. Therefore, a comparatively low aeration rate (4 vvm) capable of attaining good circulation of BSPs in the CBF was adequate for the lipase production. The effects of meat extract (main component of medium) feeding on intracellular lipase production was also examined by constant-feed rate fed-batch cultures. The results indicated that the specific feed rate of meat extract q s controlled in the range of 0.04–0.08 (g-meat extract)(g-cell) −1(h) −1 might enhance intracellular lipase activity, whereas the cellular growth in BSPs was independent of the meat extract feed rate. Therefore, the fed-batch culture in which the specific feed rate of meat extract q s was controlled at 0.05 by varying the meat extract feed rate stepwise using a microcomputer was carried out, and the intracellular lipase activity of immobilized cells could be enhanced 1.3–1.5 times that obtained in batch cultivation. The specific feed rate of meat extract q s is an effective index for the production of intracellular lipase of Rh. chinensis.