Production of lipase by Rhizopus arrhizus was studied in a rotating biological contactor(RBC)with polyurethane foam(PUF),as a porous biomass support,attached on both sides of the RBC disks.The effects of aeration rate,rotating rate of discs,volume of broth and the number of discs on the lipase activity were studied in the 6 L RBC,and the optimum fermentation condition was as follows:4 L·min-1 aeration rate,100 r·min-1 rotating rate,3.5 L medium with three discs in 6 L RBC.Repeated batch fermentation by immobilized mycelium was tested and it was found that immobilized cells showed high stability for repeated use.Five repeated batches could be carried out in 6 L RBC and the lipase productivity increased from 3125 U·h-1 in batch fermentation to 9512 U·h-1 in repeated batch fermentation,which was 3 times as high as that in batch fermentation.
