Purity of maltose-binding protein – Recombinant streptavidin expressed in Escherichia coli BL21 (pD861-MBP: 327892)

Nearly 95% of streptavidin which is expressed in Escherichia coli found as an inclusion body. Protein expressed in an inclusion body form requires further steps for the folding process related to its purification. Whereas the purity level of the recombinant streptavidin is very crucial mainly for the specification test in diagnostic system. In this study, we designed synthetic gene of streptavidin to be fused with maltose-binding protein (MBP) gene to enhance its solubility when expressed in E. coli BL21 (pD861-MBP: 327892) and purified using amylose resin with gradient column buffer. Based on the SDS-PAGE characterization, the majority of recombinant streptavidin was found in soluble than that of insoluble form. Recombinant streptavidin was found at its suitable size at 56.6 kDa in the soluble protein fraction with a concentration of 537.42 mg/L. The purest fraction of streptavidin recombinant was obtained at the 58(th) fraction in a concentration of 0.86 mg/L with purity level of 98.77%. Compared to the initial crude protein extract, the level of purity is lower, 6.03%. In summary, the MBP purification method improves the purity level and enhances the solubility of the recombinant streptavidin.