Implementation of fed-batch strategies for vitamin K (menaquinone-7) production by Bacillus subtilis natto in biofilm reactors
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Recent studies show the essential health benefits associated with vitamin K, especially menaquinone-7 (MK-7). These benefits include reducing risks of cardiovascular diseases, osteoporosis, and even cancer. However, MK-7 production on an industrial level is only possible through bacterial fermentation and also current static fermentation strategies are not potent enough with difficulties to scale up. Biofilm reactors, however, may be a practical alternative. Biofilm reactors provide a controlled environment for the microorganisms to form mature and robust biofilms that enable them to produce value-added products with enhanced efficiencies. In this study, fed-batch addition of glucose and glycerol were investigated to the base media in biofilm reactors, as carbon source addition seemed crucial in batch fermentations. Results indicated that fed-batch strategies can be significantly effective in glucose-based medium, increasing the end-product concentrations to 28.7 ± 0.3 mg/L of MK-7 which was 2.3 fold higher than the level produced in suspended-cell bioreactors and renders the biofilm reactors as a potential replacement for static fermentation strategies. Moreover, morphological changes of B. subtilis were tracked during the 12-day long fermentation runs and finally, SEM investigations confirmed significant biofilm and extracellular matrices formed on the plastic composite support (PCS) in the biofilm reactors. In conclusion, biofilm reactors especially with fed-batch fermentation regimes seem to be an effective tool for MK-7 production at industrial scales.
KeywordsMK-7 Menaquinone-7 Vitamin K Biofilm reactor Bacillus subtilis Fed-batch
The authors thank the Microscopy Facility at The Pennsylvania State University for their support in project.
This work was supported by the USDA National Institute of Food and Agriculture Federal Appropriations under Project PEN04561 and accession number 1002249.
Compliance with ethical standards
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no conflict of interest.
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