Enhanced production of xylanase by recombinant Escherichia coli DH5α through optimization of medium composition using response surface methodology

The effect of medium composition on the production of intracellular xylanase by recombinant Escherichia coli DH5α was studied in shake flask culture. The medium was optimized using response surface methodology (RSM) based on two-level fractional factorial design (2FFD) and central composite design (CCD). Initially, significant factors of the medium composition affecting xylanase production were screened using 2FFD, where the variables consisted of glucose, diammonium hydrogen phosphate [(NH₄)₂HPO ₄], dipotassium hydrogen phosphate (K₂HPO₄), potassium dihydrogen phosphate (KH₂PO₄) and magnesium sulphate (MgSO₄). The significant variables from the 2FFD [((NH ₄)₂HPO₄, K₂HPO₄ and MgSO₄] were selected further for CCD to improve the final xylanase yield. The optimum medium composition to achieve maximum xylanase activity was 15 g L^-1 glucose, 10 g L^-1 (NH₄) ₂HPO₄, 18 g L^-1 K2HPO4, 3.5 g L^-1 KH2PO4 and 1.5 g L^-1 MgSO4, with a final xylanase activity of 2,649 U mL-1. Verification experiments confirmed the validity of the proposed model, which led to an increase in xylanase production by about 74% as compared to nonoptimized medium (1,526 U mL^-1).