Screening the Effect of the Expression Medium and Growth Conditions on the Performance of Engineered Xylanase Produced by Immobilized Recombinant E. Coli

Abstract

Escherichia coli is the most prevalent host organism for the production of recombinant en-zymes. This was feasible due to the possibility of genetic modification and the availability of multiple E. coli strains as recombinant systems. The primary disadvantage of using E. coli as a host, however, is bacterial cell lysis due to tension build-up in the periplasmic space caused by the overexpression of the recombinant enzyme. Therefore, immobilization is preferable to cytoplasmic excretion for directing the expression of recombinant enzymes into the culture medium. This research investigated the effect of graphene oxide (GO) on the xylanase and β-galactosidase activity of immobilized recombinant E. coli. The effect of culture conditions (expression medium, IPTG, post induction temperature, post induction duration, agitation rate, and pH) on xylanase excretion and cell survival of an immobilized cell was studied using the one factor at a time (OFAT) method. After 24 hours of induction, using terrific broth (TB) as a medium increased xylanase excretion to 0.060 U/ml and resulted in decreased β-galactosidase activity (1.218 U/ml). Apart from that, a lower concentration of isopropyl -D-1-thiogalactopyranoside (IPTG) at 0.01 mM, a lower post-induction temperature (25°C), a 5-hour post-induction time, neutral pH, and 150 rpm significantly increased the xylanase excretion of immobilized cells with low β-galactosidase activity. This study established that immobilizing recombinant E. coli on GO may be advantageous for the excretion of recombinant proteins with a high cell viability.