Efficient production of recombinant enzymes using PVA-ecapsulated bacteria

The recombinant Escherichia coli cells which produce a thermostable alpha-amylase and a beta-galactosidase and the recombinant Bacillus brevis cells which produce a thermostable alpha-amylase, were immobilized in polyvinyl alcohol (PVA) capsules and the efficient production of the enzymes was investigated. The cell growth of E. coli in the PVA capsules declined with increasing incubation duration in methanol and may be caused by the decrease in medium pH due to oxygen transfer limitation and the decrease in available space for growth in a capsule. On the other hand, in the case of the immobilized B. brevis, the medium pH increased during cultivation and it suppressed the cell growth in the PVA capsules. In all experiments, the enzymes were released from the PVA capsules without cell leakage and cell growth outside the capsules. In the ease of the immobilized E. coli cells, the enzymes were released by the addition of glycine to the growth medium. The higher the glycine concentration, the greater the number of enzymes produced. On the other hand, the immobilized B. brevis produced the enzyme without glycine. The composition of the growth media was optimized for the enzyme production and the continuous production of the enzymes was investigated.