Enhanced production of novel halostable recombinant endoglucanase derived from the metagenomic library using fed-batch fermentation

A novel halostable endoglucanase Cel5R obtained from soil metagenomic library was cloned and expressed in Escherichia coil BL21 (DE3). In this study, we investigated the effect of dissolved oxygen concentration (DOC) on plasmid stability and effect of complex nitrogen source on the production of protein. With the increase in DOC from 30% to 50%, the production of protein also increased from 500 mg/l to 3 g/l. Besides, the addition of yeast extract and tryptone increased the production of endoglucanase up to 5 g/l. Overall, the production of endoglucanase showed an increase of 40-folds from shake flask to fed-batch fermentation. Biochemical characterization of the purified enzyme revealed that the enzyme retained its 100% catalytic activity after incubation with different concentrations of salts (NaCl, KCl, and LiCl) for 30 days, confirming it to be a halostable enzyme. It is the highest reported production of a recombinant endoglucanase, further increasing its potential for industrial applications.