Fig. 2

Selection of E. coli expression host system and expression of mature serratiopeptidase. a Bar graph showing the number of pMSrp plasmid transformants in different E. coli expression host systems. DH5-α, BL21-DE3, C43, pLysS and RDP represents the E. coli cloning and expression strains E. coli DH5-α, E. coli BL21 (DE3), E. coli C43(DE3), E. coli BL21 (DE3)-pLysS, and E. coli Rosetta (DE3)-pLysS respectively. b Representative SDS-PAGE gel lanes are showing expression of mature serratiopeptidase gene product in different E. coli expression systems. While E. coli C43(DE3) cells express protein at the correct size, in other systems, there is either no visible expression (Induced-pLysS) or degraded expression (Induced-RDP-1) unless induced at optical density > 1.0 at 600 nm (induced-RDP-2). The percentage contribution of the mature serratiopeptidase in total expressed protein either at correct molecular weight or in the degraded form is mentioned below the gel lanes. c Representative 12% SDS-PAGE gel showing total cell lysate of uninduced and induced cell fractions of E. coli C43(DE3) cells showing overexpression of protein equivalent to 50 KDa. Fractionated samples of cell lysate loaded on SDS-PAGE shows the mature serratiopeptidase expresses in the form of insoluble inclusion bodies and completely goes into the insoluble fraction; i.e., pellet