通过补加山梨醇或甘油提高Corynebacterium glutamicum谷氨酸发酵的稳定性

Bioresources and Bioprocessing 2015, 2:9

http://bioresourcesbioprocessing.springeropen.com/articles/10.1186/s40643-014-0032-6

通过补加山梨醇或甘油提高Corynebacterium glutamicum谷氨酸发酵的稳定性

Yan Cao, Zhen-ni He, Zhong-ping Shi, Mpofu Enock

National University of Singapore (Suzhou) Research Institute, China

【摘要】背景：谷氨酸棒状杆菌（Corynebacterium glutamicum）广泛应用于谷氨酸发酵，但这个菌种的发酵特性不稳定。这种不稳定性会减少这个菌种对于环境变化的耐受性从而导致异常发酵。结果：谷氨酸异常发酵时，谷氨酸在加糖后积累，导致谷氨酸最终浓度很低（50~60 g/L）。通过氧化还原电位（ORP）体现的rNAD+/rNADH值也比正常发酵低。当流加质量比为5:1的山梨醇/甘油或在初始培养基中添加10~15 g/L的山梨醇/甘油时，异常发酵有所好转。这时，谷氨酸继续合成，而谷氨酸最终浓度也能恢复至正常水平（≥72 g/L）。过程中rNAD+/rNADH、 ORP 、丙酮酸脱氢酶 (PDH)、 异柠檬酸脱氢酶(ICDH) 和细胞色素 c 氧化酶 (CcO) 活性维持在较高水平。结论：在发酵过程中，山梨醇和甘油不是碳源，而是作为增加细胞对环境耐受力和保持关键酶活性的保护剂。

Simplified metabolic pathway of glutamate synthesis and generation/consumption of NAD+ and NADH. (a) Metabolic pathway of glutamate synthesis; (b) simplified pathway of generation/consumption of NAD+ and NADH. GLC, glucose; PYR, pyruvate; Ac-CoA, acetyl coenzyme A; ICIT, isocitrate; α-KG, α-ketoglutarate; SUC, succinate; MAL, malate; OAA, oxaloacetate; PDH, pyruvate dehydrogenase; PC, pyruvate carboxylase; ICDH, isocitrate dehydrogrnase; ODHC, α-ketoglutarate dehydrogenase; GDH, glutamate dehydrogenase; CcO, cytochrome c oxidase.