Biosynthesis of cyclodextrin glucosyltransferase by immobilized Bacillus amyloliquefaciens in batch and continuous cultures

The immobilized cells of five bacterial cultures on different carriers were investigated for the production of cyclodextrin glucosyltransferase (CGTase). The entrapped cells of Bacillus amyloliquefaciens in calcium alginate showed the highest enzyme activity (70.8 U ml-1). The enzyme production with respect to alginate concentration, bead diameter, and maximal cell loading in the immobilization matrix was optimized. In repeated batch fermentation, the immobilized cells retained their ability to produce CGTase consistently over 14 cycles and the activity remain between 70 and 88 U ml-1 throughout the cycles. Continuous culture was investigated in packed-bed and fluidized-bed reactors. In packed-bed reactor, maximal productivity (23 KU l-1 h-1)with enzyme concentration of 48 U ml-1 and specific productivity of 141.8 U g wet cells-1 h-1 was attained at a dilution of 0.48 h-1. Continuous production in fluidized-bed reactor showed maximal productivity (30.4 KU l-1 h-1)with enzyme concentration of 53.0 U ml-1 and specific productivity of 230.9 U g wet cells-1 h-1 at a relatively high dilution rate of 0.57 h-1.