Li Wang1, Ning Liu1, Chenrui Yu1, Junliu Chen1, Kangjin Hong1, Yipeng Zang1, Mengmeng Wang1, Guangjun Nie2. 1. College of Biochemical Engineering, Anhui Polytechnic University, Wuhu, Anhui, 241000, People's Republic of China. 2. College of Biochemical Engineering, Anhui Polytechnic University, Wuhu, Anhui, 241000, People's Republic of China. n.g.jason@163.com.
Abstract
OBJECTIVE: To study the effect of nattokinse (NK) on the synthesis of poly(γ-glutamic acid) (γ-PGA) in Bacillus subtilis natto. RESULTS: 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. CONCLUSIONS: 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.
OBJECTIVE: To study the effect of nattokinse (NK) on the synthesis of poly(γ-glutamic acid) (γ-PGA) in Bacillus subtilis natto. RESULTS: 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. CONCLUSIONS: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.