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Coproduction of menaquinone-7 and nattokinase by Bacillus subtilis using soybean curd residue as a renewable substrate combined with a dissolved oxygen control strategy

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Abstract

Numerous physiological functions of menaquinone-7 (MK-7) act to reduce vascular calcification, suggesting that MK-7 may be a potential therapy for Alzheimer’s and Parkinson’s disease, and in this study, we attempted to increase the concentration of MK-7 synthesized by Bacillus subtilis natto, a standard nattokinase (NK) producing strain. Different Bacillus subtilis isolates demonstrated positive correlations between MK-7 and NK concentrations. Response surface methodology (RSM) was employed to optimize a culture medium for the simultaneous production of these molecules; the optimized medium contained the following components (%, w/v): soybean curd residue, 12.2; soya peptone, 5.7; lactose, 2.6; and K2HPO4, 0.6. The fermentation process was subsequently optimized based on online feedback control of fermentation process parameters. The dissolved oxygen (DO) concentration played an important role in the production of MK-7 and NK. With increased DO concentrations, the cell growth rate and NK activity increased. In contrast, at low DO concentrations, the concentration of MK-7 rapidly increased during the late fermentation stage. Thus, in this study, the production of MK-7 and NK by Bacillus subtilis was accomplished using soybean curd residue through medium optimization and DO control. This novel coproduction strategy was developed by controlling the aeration rate during the fermentation process. The concentrations of MK-7 and NK achieved in this study reached 91.25 mg/L and 2675.73 U/mL, respectively.

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Funding

This research was funded by The National High Technology Research and Development Program of China (2014AA021704) and by the Major Projects of Science and Technology in Anhui Province “Development and Demonstration of Vitamin K2 Functional Food” grant (grant no. 17030801036).

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Correspondence to Peng Wang or Zhiming Zheng.

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We declare that we have no conflict of interest. We also thank Dr. Shen, Zhiyong for his suggestions in the writing of this manuscript.

Research involving human participants and/or animals

This study does not involve human or animal experiments.

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This study does not involve human or animal experiments.

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Wang, H., Sun, X., Wang, L. et al. Coproduction of menaquinone-7 and nattokinase by Bacillus subtilis using soybean curd residue as a renewable substrate combined with a dissolved oxygen control strategy. Ann Microbiol 68, 655–665 (2018). https://doi.org/10.1007/s13213-018-1372-9

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  • DOI: https://doi.org/10.1007/s13213-018-1372-9

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