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 (CGTas e). The entrapped cells of Bacillus amyloliquefaciens in calcium alginate s howed the highest enzyme activity (70.8 U ml(-1)). The enzyme production wi th respect to alginate concentration, bead diameter, and maximal cell loadi ng in the immobilization matrix was optimized. In repeated batch fermentati on, the immobilized cells retained their ability to produce CGTase consiste ntly over 14 cycles and the activity remain between 70 and 88 U ml(-1) thro ughout the cycles. Continuous culture was investigated in packed-bed and fl uidized-bed reactors. In packed-bed reactor, maximal productivity (23 KU l( -1) h(-1)) with enzyme concentration of 48 U ml(-1) and specific productivi ty 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 productivi ty (30.4 KU l(-1) h(-1)) with enzyme concentration of 53.0 U ml(-1) and spe cific productivity of 230.9 U g wet cells(-1) h(-1) at a relatively high di lution rate of 0.57 h(-1). (C) 2000 Elsevier Science S.A. All rights reserv ed.