College of Biochemical Engineering, Anhui Polytechnic University, Wuhu, Anhui, 241000, People's Republic of China.
Biotechnol Lett. 2020 Nov;42(11):2285-2291. doi: 10.1007/s10529-020-02941-x. Epub 2020 Jun 28.
To study the effect of nattokinse (NK) on the synthesis of poly(γ-glutamic acid) (γ-PGA) in Bacillus subtilis natto.
γ-PGA yield significantly decreased as NK was added in the original medium. With the increment of NK dosage, the yield decreased increasingly, but biomass increased instead of decreasing. The fact that cell density triggers the synthesis of γ-PGA is a controversial issue. γ-PGA yield and biomass closely correlate with addition time of NK. The later the addition of NK, the more γ-PGA yield decreased but the more biomass increased. It is concluded that cell hunger is a key factor to trigger the transmission of the cell density signal, and NK may inhibit γ-PGA synthesis by alleviating cell hunger. Besides, NK may reduce γ-PGA yield by degrading extracellular γ-PGA molecules. The study of adding L-glutamate of 0-20 g/L to the original medium showed that low concentration of L-glutamate (less than 5 g/L) could promote the synthesis of NK and γ-PGA, and thus NK may inhibit γ-PGA synthesis through strengthening substrate competition.
NK mainly inhibits γ-PGA synthesis in Bacillus subtilis natto through alleviating cell starvation and strengthening substrate competition, and reduces γ-PGA yield through degrading extracellular γ-PGA molecules.
研究纳豆激酶（NK）对纳豆芽孢杆菌合成聚γ-谷氨酸（γ-PGA）的影响。
在原培养基中添加 NK 会导致 γ-PGA 产量显著下降。随着 NK 剂量的增加，产量逐渐下降，而生物量增加而不是减少。细胞密度触发 γ-PGA 合成这一事实是一个有争议的问题。γ-PGA 产量和生物量与 NK 的添加时间密切相关。添加 NK 的时间越晚，γ-PGA 的产量下降越多，但生物量增加越多。可以得出结论，细胞饥饿是触发细胞密度信号传递的关键因素，NK 可能通过缓解细胞饥饿来抑制 γ-PGA 的合成。此外，NK 可能通过降解细胞外 γ-PGA 分子来降低 γ-PGA 的产量。研究向原培养基中添加 0-20 g/L 的 L-谷氨酸表明，低浓度的 L-谷氨酸（小于 5 g/L）可以促进 NK 和 γ-PGA 的合成，因此 NK 可能通过加强底物竞争来抑制 γ-PGA 的合成。
NK 主要通过缓解细胞饥饿和加强底物竞争来抑制纳豆芽孢杆菌中 γ-PGA 的合成，并通过降解细胞外 γ-PGA 分子来降低 γ-PGA 的产量。
