Abstract: Development in molecular biologyhave greatly streamlined process of protein expression. One such development isautoinduction of recombinant proteins during fermentation step of bacteriallyderived protein expression. It gives ease of operation as there is no need tomonitor cell growth. This system often increases cell mass along with targetprotein yield. Many efforts have gone into specialized media preparation topromote autoinduction of recombinant proteins. The current work focuses onchanging the concentration of Luria Bertani broth components to achieveautoinduction. This phenomenon was demonstrated using staphylokinase (SAK) asrepresentative protein. The SAK gene from S.aureus was 411 bp and yielded aprotein of 15 kDa when expressed using pET21a vector in E. coli. BL21 (DE3)cells. The recombinant SAK (rSAK) was soluble in nature. Fermentation studieswere carried out to optimize various parameters (media optimization, eliminationof inducer, autoinduction time optimization, etc.) for maximizing the yield ofrSAK. When optimal concentration of tryptone and yeast extract was used duringfermentation process, the protein expression was achieved without using IPTG.The rSAK yield through autoinduction was comparable to the protein expressionwhen inducer was used during fermentation. The protein was purified by ionexchange chromatography using single step purification. The thrombolyticactivity of the purified rSAK was successfully demonstrated.

Keywords: Staphylokinase,Autoinduction, Hyperexpression, Single step protein purification without tag.