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.

中文翻译：

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纳豆激酶抑制纳豆枯草芽孢杆菌中聚（γ-谷氨酸）的产生

研究纳豆激酶（NK）对纳豆枯草芽孢杆菌中聚（γ-谷氨酸）（γ-PGA）合成的影响。随着在原始培养基中加入 NK，γ-PGA 产量显着降低。随着NK用量的增加，产量逐渐下降，但生物量不减反增。细胞密度触发γ-PGA 合成的事实​​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。NK加入越晚，γ-PGA产量下降越多，但生物量增加越多。结论细胞饥饿是触发细胞密度信号传递的关键因素，NK可能通过减轻细胞饥饿来抑制γ-PGA合成。此外，NK可能通过降解细胞外γ-PGA分子来降低γ-PGA产量。在原培养基中加入 0~20 g/L 的 L-谷氨酸的研究表明，低浓度的 L-谷氨酸（小于 5 g/L）可促进 NK 和 γ-PGA 的合成，因此 NK 可能抑制通过加强底物竞争合成γ-PGA。NK主要通过减轻细胞饥饿和加强底物竞争抑制纳豆枯草芽孢杆菌γ-PGA合成，并通过降解细胞外γ-PGA分子降低γ-PGA产量。