[Study on the repeated batch fermentation of lipase by immobilized Rhizopus].

Repeated batch fermentation with Rhizopus arrhizus immobilized by polyurethane was optimized in details including the time to replace, the volume of the replaced medium and the optimal composition of the medium to replace. Immobilized cells showed stability for repeated use. Immobilized cells could be used for 9 batches, lasting 140h in flask and 6 batches in 5L fermenter when the substitute culture medium consisted of (%): soybean flour 3.0, earthnut oil 0.5 and the liquid was replaced by 40% . The time for fermentation was reduced largely and the lipase productivity was 3 - 6 times as high as that in batch fermentation.