immobilization of penicillin g acylase using permeabilized escherichia coli whole cells within chitosan beads

entrapment of permeabilized whole cells within a matrix is a common method for immobilization. chitosan possesses distinct chemical and biological properties, which make it a suitable matrix for entrapment and immobilization of penicillin g acylase (pga). in the first step, escherichia coli (atcc 11105) cells were permeabilized using n-cetyl-n,n,n-trimethyl ammonium bromide (ctab) (0.1% w/v, 45 min, 45 rpm) which then immobilized using glutaraldehyde (5% w/v) as cross-linker and chitosan (3% w/v) as the matrix. these conditions were established after preliminary trials with ctab and glutaraldehyde concentrations in the range of 0.05-0.25% w/v and 1-9% v/v, respectively. the hydrolytic activity was assayed using ehrlich reagent. permeabilization of cells caused 9% increase in penicillin g acylase (pga) conversion after 15 min compared to the intact cells. although, immobilization on chitosan decreased the conversion compared to un-immobilized treated cells (13%), the new biocatalyst showed acceptable operational stability, maintaining more than 90% of the initial activity after 20 cycles. optimum conditions for immobilization of e. coli cells were: ctab 0.1% w/v and glutaraldehyde 5% v/v. a new combination method was successfully developed and optimized for immobilization of treated whole cells on chitosan matrix.