Screening, breeding and metabolic modulating of a strain producing succinic acid with corn straw hydrolyte
Screening, breeding and metabolic modulating of a strain producing succinic acid with corn straw hydrolyte
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DOI：
10.1007/s11274-008-9936-7
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发表时间：
2009-04-01
影响因子：
4.1
通讯作者：
Weng, Shibing
中科院分区：
文献类型：
--
作者：
Li, Xingjiang;Zheng, Zhi;Weng, Shibing
目的研究玉米秸秆水解产物琥珀酸的工业生物转化高产突变菌株。方法采用API生化反应和16S r RNA序列分析进行鉴定，然后对菌株的代谢途径及其相关酶进行代谢通量分析（MFA）。引进同步辐射x射线和定点诱变技术减少了这些副产物，并对代谢工艺进行了调整。结果经鉴定，产琥珀酸菌株S.JST属琥珀酸放线杆菌属。代谢途径分析表明，该菌株具有同时利用葡萄糖和木糖的特点，考虑到大多数作物秸秆水解产物含有葡萄糖和木糖，这是一个很大的优势。代谢通量分析表明乙酸和酒精与琥珀酸通量竞争，[H]还原能量平衡分析表明细胞内产生的[H]电子供体不足以进行琥珀酸的代谢。x射线诱变结果表明，突变菌株M.JSTP的副产物乙酸通量从1.233 mmol/g DW h下降到0.666，在磷酸转乙酰化酶基因pta中发现了两个突变位点，但由于[h]还原力的供应严重不足，琥珀酸的产量减少。突变体M.JSTA的琥珀酸通量较亲本S.JST从2.480 mmol/g DW h提高到3.163 mmol/g DW h，在HMP与EMP的通量比周围，通过添加柠檬酸调节代谢工艺以改善[h]还原能力的平衡，将副产物醇通量从1.303 mmol/g DW h降低到0.029 mmol/g DW h。结论本文所获得的突变株值得大规模推广。
Purpose In this paper, the high yield mutant strain was expected to be obtained for the industrial bioconversion of corn straw hydrolyte to succinic acid. Methods API biochemical reactions and 16S r RNA sequence analysis were carried out for identification, and then the strain's metabolic pathway and its relevant enzymes were discussed for the metabolic flux analysis (MFA). The X-ray of synchronous radiation and site-directed mutagenesis were imported for decreasing those byproducts, and the metabolic technics was also modulated. Results Identification showed that the succinic-acid-producing strain S.JST belonged to Actinobacillus succinogenes species. Metabolic pathway analysis indicated that this strain had the character of utilizing glucose and xylose simultaneously, which was a great advantage considering the fact that most crop straw hydrolyte included glucose and xylose. Metabolic flux analysis showed that acetic acid and alcohol competed with the flux of succinic acid, and the analysis of [H] reducing power balance investigated that the [H] electronic donor produced in the cell was not enough for the metabolism of succinic acid. Then X-ray mutagenesis showed that the flux of byproduct acetic acid was decreased to 0.666 from 1.233 mmol/g DW h and that two mutated sites were found in pta (gene of phosphotransacetylase) from mutant strain M.JSTP, but less succinic acid was produced due to the worse lacking in the supply of [H] reducing power. The site-directed mutagenesis showed that the flux of byproduct alcohol was successfully decreased to 0.029 from 1.303 mmol/g DW h. Then, surrounding the flux ratio of HMP to EMP, the metabolic technics was modulated with the addition of citrate in order to improve the balance of [H] reducing power, thus the succinic acid flux of the mutant M.JSTA was increased to 3.163 from 2.480 mmol/g DW h comparing with the parent strain S.JST. Conclusions The mutant strain obtained in this paper deserves to be scaled-up.