Production of cyclodextrin by poly-lysine fused Bacillus macerans cyclodextrin glycosyltransferase immobilized on cation exchanger

Bacillus macerans cyclodextrin glycosyltransferase (CGTase) fused with 10 lysine residues at its C-terminus (CGTK10ase) was immobilized onto a cation exchanger by ionic interaction and used to produce α-cyclodextrin (CD) from soluble starch. Poly-lysine fused immobilization increased the V _m of the immobilized CGTase by 40% without a change in K_m. The activation energies of thermal deactivation (E_a) were 41.4, 28.1, and 25.9 kcal mol^-1, respectively, for soluble wild-type (WT) CGTase, soluble CGTK10ase, and immobilized CGTK10ase, suggesting destabilization of CGTase by poly-lysine fusion and immobilization onto a cation exchanger. Maximum α-CD productivity of 539.4 g l^-1 h^-1 was obtained with 2% soluble starch solution which was constantly fed at a flow rate of 4.0 ml min^-1 (D = 240 h^-1) in a continuous operation mode of a packed-bed reactor. The operational half-life of the packed-bed enzyme reactor was estimated 12 days at 25°C and pH 6.0.