PRODUCTION OF BACILLUS-THURINGIENSIS SPORES IN TOTAL CELL RETENTION CULTURE AND 2-STAGE CONTINUOUS-CULTURE USING AN INTERNAL CERAMIC FILTERSYSTEM

The production of Bacillus thuringiensis spores was investigated in a bioreactor incorporating a ceramic membrane filter to improve spore co ncentration and volumetric productivity. Two cultivation methods were used in this study: a total cell retention culture (TCRC), and a two-s tage continuous culture with partial cell bleeding. In the TCRC, fed b y 50 g/L of glucose, a spore concentration of 1.6 x 10(10) CFU/mL was obtained with a spore percentage of greater than 95% and a maximum cel l mass of 82.2 g/L. The volumetric productivity was four times higher than that obtained from batch cultivation. In the two-stage continuous culture with partial cell bleeding spore concentration was strongly d ependent on the bleed ratio. The spore concentration of 1.8 x 10(9) CF U/mL and the spore percentage of 70% were obtained at the second stage when a bleed ratio of 0.33 and a dilution rate of 0.23 h-1 were used. (C) 1993 John Wiley & Sons, Inc.