Production of soluble recombinant proteins in Escherichia coli: Effects of process conditions and chaperone co-expression on cell growth and production of xylanase

In this study, effects of temperature, inducer concentration, time of induction and co-expression of molecular chaperones (GroEL–GroES and DnaKJE), on cell growth and solubilization of model protein, xylanases, were investigated. The yield of soluble xylanases increased with decreasing cultivation temperature and inducer level. In addition, co-expression of DnaKJE chaperone resulted in increased soluble xylanases though the time of induction of chaperone and target protein had a bearing on this yield. A combination of chaperone co-expression and partial induction resulted in ∼40% (in DnaKJE) and 33% (in GroEL–GroES) of total xylanase yield in soluble fraction. However, the conditions for maximum yield of soluble r-XynB and maximum % soluble expression of r-XynB were different. Higher expression of soluble xylanases in a scalable semi-synthetic medium showed potential of the process for soluble enzyme production.