Abstract：
Menaquinone-7 (MK-7) is an important class of vitamin K2 that is essential in human health and can prevent osteoporosis and cardiovascular disease. However, due to the complex synthesis pathway, the synthesis efficiency is low. The main objective of this study was to explore the effect of enhanced supply of precursors in Bacillus natto. Three precursors of pyruvate, shikimic acid, and sodium glutamate were chosen to investigate the effect of enhanced supply of precursors on MK-7 synthesis. Then, the optimal concentrations, different combinations, and different adding times were systematically studied, respectively. Results showed that the combination of shikimic acid and sodium glutamate could boost MK-7 production by 2 times, reaching 50 mg/L of MK-7 titer and 0.52 mg/(L·h) of MK-7 productivity. Furthermore, adding shikimic acid and sodium glutamate initially and feeding pyruvate at 48 h and 72 h increased MK-7 production to 58 mg/L. At the same time, the expression of the three related genes was also significantly upregulated. Subsequently, a new fermentation strategy combining the precursors enhancement and product secretion was proposed to enhance MK-7 yield and MK-7 productivity to 63 mg/L and 0.45 mg/(L·h). This study proposed a new fermentation regulation strategy for the enhancement of vitamin K2 biosynthesis.
摘要：
Menaquinone-7（MK-7）是一类重要的维生素K2，对人体健康至关重要，可以预防骨质疏松症和心血管疾病。然而,由于复杂的合成途径，合成效率较低。本研究的主要目的是探索纳豆芽孢杆菌前体强化供应的效果。丙酮酸盐的三种前体，莽草酸,选择了谷氨酸钠来研究前体供应增加对MK-7合成的影响。然后，最佳浓度，不同的组合,系统研究了不同的添加时间，分别。结果表明，莽草酸和谷氨酸的组合可以使MK-7的产量提高2倍，达到50mg/L的MK-7滴度和0.52mg/（L·h）的MK-7生产率。此外，最初添加莽草酸和味精，并在48h和72h饲喂丙酮酸盐，将MK-7的产量提高到58mg/L。同时,三个相关基因的表达也显著上调。随后，提出了一种结合前体增强和产物分泌的新发酵策略，以将MK-7产量和MK-7生产率分别提高到63mg/L和0.45mg/（L·h）。本研究提出了一种新的发酵调控策略，用于增强维生素K2的生物合成。
