Background: The effect of milking menaquinone-7 (MK-7) with biocompatible organic solvents on MK-7 production in B. subtilis fermentation was studied. Periodic milking of MK-7 from the fermentation medium by n-hexane significantly enhanced the total MK-7 production ~ 1.7 fold at the end of 72 hours of fermentation (p < 0.05) as compared to the control medium.
Methods: Milking of MK-7 with a mixture of n-hexane phase modified with n-butanol was also explored. Although milking of MK-7 by a mixture of n-hexane and n-butanol (1:2, v/v), was found to be appropriate in terms of high extraction capacity, no significant increase in total MK-7 concentration was observed. Biocompatibility between the extraction solvents and B. subtilis was also examined.
Results and Conclusion: The results indicated that the mixture of n-hexane and n-butanol exhibited some detrimental effects. However, n-hexane alone exhibited delayed toxicity starting at 84 hours of periodic milking and could, therefore, be considered as the most promising organic solvent for milking MK-7 in B. subtilis fermentation while enhancing the productivity of the system.