Expression of His-tagged NADPH-dependent acetoacetyl-CoA reductase in recombinant Escherichia coli BL-21(DE3).

Poly-3-hydroxybutyrate (P(3HB)), a member of the polyhydroxyalkanoate (PHA) family, is a biodegradable polyester with diverse industrial applications. NADPH-dependent acetoacetyl-CoA reductase (pha B) is the enzyme which plays an essential role in P(3HB) synthesis by catalyzing the conversion of the intermediates. The expression of pha B enzyme using the recombinant Escherichia coli BL-21(DE3) and the purification of the synthesized enzyme were studied. The pET-B3 plasmid harbouring the pha B gene derived from Ralstonia eutropha H16, was driven by the lac promoter in E. coli BL-21(DE3). The enzyme was expressed with different induction time, temperatures and cell age. Results showed that the cell age of 4 h, induction time of 12 h at 37°C were identified as the optimal conditions for the enzyme reductase expression. A specific activity of 0.151 U mg−1 protein and total protein concentration of 0.518 mg mg−1 of dry cell weight (DCW) were attained. Affinity chromatography was performed to purify the His-tagged pha B enzyme, in which enhanced the specific activity (14.44 U mg−1) and purification fold (38-fold), despite relative low yield (44.6%) of the enzyme was obtained. The purified pha B showed an optimal enzyme activity at 30°C and pH 8.0. The findings provide an alternative for the synthesis of the reductase enzyme which can be used in the industrial-scale production of the biodegradable polymers. • The His-tagged pha B was successfully expressed in recombinant Escherichia coli BL-21(DE3). • Affinity chromatography was applied for the purification of His-tagged pha B enzyme. • Specific activity and purification fold of purified pha B enzyme was notably enhanced. [ABSTRACT FROM AUTHOR]