Different effects of bacterial host strains and inducers on expressing of two recombinant antibacterial protein

Selecting suitable bacterial host strain and using of proper inducer also is one of the most imporatnt challenges in soluble recombinant proteins production. One of the main strains used for recombinant protein expression is E.coli BL۲۱(DE۳) since it lacks OmpT and Lon genes. Also E.coli BL۲۱(DE۳)pLysS has T۷ lysozyme gene and is used for expressing of recombinant protein with toxicity effect on host. Therefore, in this study an engineered recombinant fusion protein with peptidoglycan hydrolysis effect (P-R) and a not engineered protein (P) as control were expressed in E. coli BL۲۱(DE۳) and BL۲۱(DE۳)pLysS using pET expression system in presence of IPTG or lactose as inducer. First, BL۲۱(DE۳) harboring P-R and P were separately cultured in Luria Bertani broth medium and both hosts at OD~۰.۵ were induced with IPTG ۱ mM and incubated overnight at ۳۷ oC and ۲۲۰ rpm. In addition, to investigate the effect of lactose as inducer, both bacteria were cultured first in a non-inducing lactose-free media as a preculture and then in an auto-inducing media containing glucose, lactose and glycerol as previous conditions. The expression of normalized samples was analyzed using SDS-PAGE and compared with ImageJ program. The expression amount of P-R engineered protein in auto-inducing media was ۱.۱۴۶ mg/ml, which was more than twice of when IPTG was used as inducer. However, P protein, showed better expression in LB medium. In addition, expression of P gene in BL۲۱(DE۳)pLysS was ۳۴ times more than BL۲۱(DE۳). Due to higher expression of engineered protein in BL۲۱ (DE۳) with lactose as inducer, IPTG was replaced with lactose as expression inducer. This issue is more important in industrial scale. Besides cost, using of lactose as inducer allows to easier producing process because of it is not required to monitor of optical density. However, different proteins show dissimilar behavior in equal conditions.

کلیدواژه ها:

Fusion protein ، Auto-inducing media ، IPTG ، Lactose ، E. coli