Authors: Xingjiang Li Zhi Zheng Zhaojun Wei Shaotong Jiang Lijun Pan Shibing Weng
Publish Date: 2008/12/16
Volume: 25, Issue: 4, Pages: 667-677
Abstract
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 Xray of synchronous radiation and sitedirected mutagenesis were imported for decreasing those byproducts and the metabolic technics was also modulated Results Identification showed that the succinicacidproducing strain SJST 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 Xray mutagenesis showed that the flux of byproduct acetic acid was decreased to 0666 from 1233 mmol/g DW h and that two mutated sites were found in pta gene of phosphotransacetylase from mutant strain MJSTP but less succinic acid was produced due to the worse lacking in the supply of H reducing power The sitedirected mutagenesis showed that the flux of byproduct alcohol was successfully decreased to 0029 from 1303 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 MJSTA was increased to 3163 from 2480 mmol/g DW h comparing with the parent strain SJST Conclusions The mutant strain obtained in this paper deserves to be scaledupThis work was supported by Key Technology RD Program of china 2007BAD34B01 the Natural Science Foundation of Anhui Province of China 070411024 and the Foundation of Hefei University of Technology of China 073002F We appreciate helpful comments provided by the anonymous reviewers We thank Dr Harshini Gheens Center on Aging University of Louisville School of Medicine for making a thorough language correction and Dr Sun JiuSong Department of Medicine Brigham and Women’s Hospital and Harvard Medical School for helping to revise this manuscript
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