抗氧化胁迫促进地衣芽孢杆菌合成杆菌肽

地衣芽孢杆菌（Bacillus licheniformis）发酵合成杆菌肽过程中存在的氧化胁迫影响了杆菌肽的合成效率。添加0.2%抗坏血酸和0.4%半胱氨酸使杆菌肽效价在摇瓶水平分别比对照提高了20.7%和29.4%。另外，胞内过氧化氢酶活比对照分别降低了68.3%和43.8%。半胱氨酸合成加强工程菌株在10 L罐发酵过程中，峰值生物量（84×109 CFU/mL，26 h）比出发菌株提高了9.0%，杆菌肽效价（1 090 U/mL，32 h）也提高了13.5%。Cys含量（213.3 mg/L，24 h）和过氧化氢酶活力（14～32 h）分别比对照提高了约60%和降低了15%～40%。说明Cys作为前体氨基酸参与杆菌肽合成与参与氧化自由基清除之间存在竞争关系，工程菌株通过增强Cys合成更好地满足了细胞对两者的生理需求，维持了细胞活性、促进了杆菌肽合成效率。

Oxidative stress promoted bacitracin biosynthesis by Bacillus licheniformis

The oxidative stress, existing in the fermentation process of Bacillus licheniformis for bacitracin production, affected the bacitracin synthesis efficiency. The addition of VC 0.2% and cysteine (Cys) 0.4% in shake flask fermentation promoted bacitracin production by 20.7% and 29.4%, respectively. Moreover, the intracellular catalase activity was 68.3% and 43.8% lower than the control, respectively. During the fermentation process of B. licheniformis CY in a 10 L bioreactor, the maximum biomass and bacitracin production was 84×109 CFU/ml at 26 h and 1 090 U/ml at 32 h, which was 9.0% and 13.5% higher than that of strain LC, respectively. Meanwhile, the Cys content was 213.3 mg/L at 24 h, which was 60% higher than that of strain LC; the catalase activity was 15%-40% lower than that of strain LC at 14-32 h. The results suggested that a competitive relationship existed between Cys as a precursor amino acid to participate in bacitracin synthesis and to participate in the oxidative stress response in cells. The genetic engineering strain CY fulfilled the physiological demands mentioned above better by enhancing the synthesis efficiency of Cys, which maintained cell vitality and facilitated bacitracin biosynthesis efficiency.