Semi-continuous and continuous riboflavin production by calcium-alginate-immobilized Candida tropicalis in concentrated rectified grape must

Candida tropicalis cells were immobilized in calcium alginate. Gel beads were used to inoculate a medium containing concentrated rectified grape must as the sole carbohydrate source for both semi-continuous and continuous riboflavin production, in a 1 litre glass stirred-tank fermenter. In semi-continuous mode, vitamin B-2 concentrations in culture broth ranged from approximately 350 to 650 mg.l(-1) in successive runs. In continuous mode, concentrations of about 400-600 mg.l(-1) were observed in the effluent for more than 1 month without significant loss of flavinogenic activity. The highest value of both vitamin B-2 production and sugar bioconversion occurred at the lowest dilution rate (0.008 h(-1)).