Production of Bacillus thuringiensis spores in total cell retention culture and two‐stage continuous culture using an internal ceramic filter system

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Abstract
The production of Bacillus thuringiensis spores was investigated in a bioreactor incorporating a ceramic membrane filter to improve spore concentration and volumetric productivity. Two cultivation methods were used in this study: a total cell retention culture (TCRC), and a two‐stage continuous culture with partial cell bleeding. In the TCRC, fed by 50 g/L of glucose, a spore concentration of 1.6 × 1010 CFU/mL was obtained with a spore percentage of greater than 95% and a maximum cell 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 dependent on the bleed ratio. The spore concentration of 1.8 × 109 CFU/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. © 1993 John Wiley & Sons, Inc.