Fermentative Production of Engineered Cationic Antimicrobial Peptide from Economically Feasible Bacterial Host E. coli GJ1158

Abstract

Production of antimicrobial peptides has gained lot of significance in the present day research. Most of the recombinant proteins are generally produced from IPTG inducible E. coli BL21(DE3). As an alternative, considering the factors like cost and toxic nature of IPTG, salt inducible Escherichia coli GJ1158 was used in the present study for the production of synthetic cationic antimicrobial peptide by fed batch fermentation. This study was conducted to optimize the physico–chemical parameters viz., dissolved oxygen concentration (DOC) and nutritional factors viz., carbon, nitrogen and phosphate sources on bacterial growth and peptide production. Even after increase in DOC more than 30 % in batch culture has no effect on expression, but significant improvement in fed-batch cultivation was observed beyond 30% DOC. Supplementation of production medium with different pulses of nutrient sources like dextrose mono hydrate, yeast extract and Na2HPO4 enhanced the expression in fed batch fermentation process even without disturbing the cell growth at 40 % DOC. When growth reached 15 g/L of dry cell weight, culture was induced with 150 mM NaCl and further cultured for next 15 hr (16.37 g/L dry cell weight). Approximately, 258 mg/L of pure peptide was obtained by using modified GYEON medium. The peptide thus produced is tested for its antimicrobial activity, devoid of hemolytic activity. The fed-batch fermentation which emphasizes, this was the highest reported concentration of recombinant synthetic peptide from salt inducible expression host till to date, which manages to gratify the present day industrial production of the peptides cost-effectively.