Optimization of culture conditions to express AA9 Polysaccharide monooxygenases AN3860 in Escherichia coli

Abstract

Lignocellulose biomass is a copious source for second generation biomaterial production. The participant of Polysaccharide monooxygenases enzyme (PMO) in the reactions which convert lignocellulose biomass into monosaccharides enhances the activity and improve the efficiency of hydrolysis of hydrolase enzymes on lignocellulose substrate. Enzyme AN3860, obtained from Aspergillus nidulans strain belonging to AA9 PMO, is expected to catalyze flexibly at C1 and C4 carbon positions of β-glycosidic linkage. As an enzyme with high potential of improving cellulose crystals hydrolysis capacity, AN3860 was successfully cloned into the expression system of E. coli BL21 (DE3) strain. In this study, the culture process of recombinant strain with AN3680 gene is optimized to increase the target proteins yield, thus ensure the outcome of purification process, and save production cost. The results demonstrate that the E. coli recombinant strains grow sufficiently in TB (Terrific Broth) culture media and the highest yield of AN3680 protein achieved when the concentration of Isopropyl β-D-1-thiogalactopyranoside (IPTG) is 0.05 mM and the temperature of the reaction is 30 ⁰C at 150 rpm. After 6 hours of induction, the biomass reaches 500 mg/L and the yield of AN3860 account for (7-10) % total protein generated. The recombinant AN3860 protein is later harvested on larger scale and purified by Ni-NTA column chromatography method for analysis of bioactivities on lignocellulose substrates in the future.

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