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Enhanced production of dimethyl phthalate-degrading strain Bacillus sp. QD14 by optimizing fermentation medium
Mo, Jixian; Wang, Zhigang; Xu, Weihui; Li, Shanshan & Yu, Zhidan
Abstract
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 × 108 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.
Keywords
Bacillus; Box–Behnken design; Dimethyl phthalate; Medium optimization; Plackett–Burman design
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