Actinobacillus succinogenes抗氟乙酸突变株的选育及其代谢流量分析

Breeding of Monofluoroacetate-resistant Strains of Actinobacillus succinogenes and the Mechanism Based on Metabolic Flux Analysis

摘要:

琥珀酸是一种用于合成树脂、可降解塑料及许多化学中间体的重要绿色化工原料。为了提高琥珀酸的发酵产率, 基于Actinobacillus succinogenes的代谢流量分布情况对其育种机制进行了研究。以Actinobacillus succinogenes CGMCC1593为原始菌株进行NTG诱变, 挑选在含有50~100 mmol/L氟乙酸平板生长较快的菌落, 经过初筛和复筛, 发现SF-9菌株产生更多琥珀酸且积累乙酸较少。以50 g/L的葡萄糖为碳源, 在5 L发酵罐上进行分批发酵, 该菌株发酵32 h时琥珀酸产量(34.8 g/L)提高了23.4%, 琥珀酸/乙酸比率为9:1, 副产物乙酸量比原始菌株降低了约50%。代谢流量分析(MFA)结果表明, PEP是影响琥珀酸合成的关键节点, PYR是影响乙酸等杂酸生成比例的关键节点, 并且这两个节点均非刚性节点。通过氟乙酸抗性诱变, 成功地筛选出了流向乙酸、甲酸和乳酸等杂酸的流量相对减少, 而流向琥珀酸的流量明显增强的突变菌株SF-9。

Abstract:

Succinic acid has received a great deal of attention as an important green chemical stock for the manufacture of synthetic resins, biodegradable polymers and chemical intermediates. In this paper, the breeding mechanism of Actinobacillus succinogenes based on metabolic flux analysis was demonstrated to improve the yield of succinic acid by fermentation. After the NTG treatment, mutants from A. succinogenes CGMCC 1593 which were able to grow in medium containing concentrations of about 50~100 mmol/L of sodium monofluoroacetate were obtained. Among them, a mutant SF-9 was selected for producing more succinic acid and less acetic acid. When fermentations were conducted in a 5 L bioreactors, the final succinic acid concentration of SF-9 (34.8 g/L) increased 23.4%, and the mass ratio of succinic acid/acetic acid increased from 3.3 to 9 compared with those of the parent strain. Based on the metabolic flux analysis of A. succinogenes, PEP was found to be a key node which has an important effect on the production of succinic acid, and the flux ratio of by-productions (acetic, formic, lactic acid) was influenced by PYR node. Compared with the parent strain, the flux to succinic acid of mutant (A. succinogenes SF-9) was significantly increased, while the flux to by-productions had an obvious decline. Therefore, PEP and PYR are not rigid nodes in the metabolic regulation of A. succinogenes.