Enhanced production of dimethyl phthalate-degrading strain Bacillus sp. QD14 by optimizing fermentation medium
Background Integrated statistical experimental designs were applied to optimize the medium constituents for the production of a dimethyl phthalate (DMP)-degrading strain Bacillus sp. QD14 in shake-flask cultures. A Plackett-Burman design (PBD) was applied to screen for significant factors, followed by the Steepest Ascent Method (SAM) to find the nearest region of maximum response. A Box-Behnken design (BBD) of the Response Surface Methodology (RSM) was conducted to optimize the final levels of the medium components. Results After the regression equation and response surface contour plots were analyzed, the concentrations of glucose, corn meal and NaCl were found to significantly influence the biomass of DMP-degrading bacteria. A combination of 22.88 g/L of glucose, 11.74 g/L of corn meal, and 10.34 g/L of NaCl was optimum for maximum biomass production of Bacillus sp. QD14. A 57.11% enhancement of the biomass production was gained after optimization in shake-flask cultivation. The biomass production of Bacillus sp. QD14 reached 9.13 ± 0.29 × 10(8) CFU/mL, which was an excellent match for the predicted value, and the mean value of the match degree was as high as 99.30%. Conclusion In this work, the key factors affected by the fermentation of DMP-degrading strain Bacillus sp. QD14 were optimized by PBD, SAM and BBD (RSM); the yield was increased by 57,11% in the conditions in our study. We propose that the conditions optimized in the study can be applied to the fermentation for commercialization production.