Improved stability and reusability of cotton-immobilized recombinant Escherichia coli producing US132 Cyclodextrin Glucanotransferase

Recombinant Escherichia coli / pAD26 cells were optimally immobilized on cotton to obtain plasmid stability. An experimental design that monitored two major responses, namely stability and reusability, was applied for screening the factors affecting the immobilization of the strain (cylodextrin, sucrose, shape support, mass of cotton matrices, mass of initial biomass, age of biomass, ethylenediamine, glutaraldehyde, and incubation time) and the optimization of the most significant variables. The optimal values recorded for the two criteria were obtained with high glutaraldehyde concentration (0.15 %) and early inoculum age (2 h) in the presence of 0.2 mM cylodextrin. With those optimum conditions, cyclodextrin glucanotransferase production yields were enhanced, reaching up to 39.77 U/mL. The stability and reusability of the immobilized strain were two fold and three fold higher, respectively, than those of the control after three cycles.