β-Alanine,the only kind of β amino acid which exists naturally,has important applications in medicine,food and chemical industry.In this study,the possibility of metabolic engineering of Escherichia coli for the production of β-alanine was investigated.The Escherichia coli CICIM B0016-050 (ackA-pta pflB adhEfrdA ldhA) strain with deletions on synthetic pathways of acetic acid,formic acid,ethanol,succinic acid and lactic acid,was used as the starting strain.Effects of gene knockouts of lysC (encoding aspartokinase),panC (encoding pantothenate synthetase) and ptsG (encoding the major glucose transporter IICB (Glc)) and overexpression of the Corynebacterium glutamicum panD gene (encoding L-aspartate-α-decarboxylase) on synthesis of β-alanine in B0016-050 were investigated.The synthesis of β-alanine was improved by 12.5％,39.3％ and 13.3％,respectively,after combined gene knockouts,and was increased by more than 100.6 times after overexpressing the panD gene.After optimization of fermentation conditions,the yield of β-alanine in the shake flask fermentation of strain B0016-080BB/pPL-panD reached 5.0 ±0.2 g/L,and the volume productivity was 0.12 ±0.01 g/(L · h).The results laid the foundation for fermentation of β-alanine.%β-丙氨酸是天然存在的唯一一种β型氨基酸,在医药、食品、化工等领域有重要应用.该研究考察了以重组Escherichia coli发酵合成β-丙氨酸的可能性.在敲除副产物乙酸、甲酸、乙醇、琥珀酸、乳酸合成途径编码基因的Escherichia coli CICIM B0016-050(ackA-pta pflB adhE frdA ldhA)菌株中,考察叠加敲除β-丙氨酸的竞争途径天冬氨酸激酶、泛酸合成酶和葡萄糖转运蛋白(EⅡCBGlc)的编码基因(lysC、panC、ptsG)以及过表达来源于Corynebacterium glutamicum的panD基因对合成β-丙氨酸的影响.结果表明,叠加敲除上述基因后,β-丙氨酸的合成量依次提高了12.5％、39.3％和13.3％;过量表达panD基因,β-丙氨酸合成量提高了86.2倍;经发酵条件优化,菌株B0016-080BB/pPL-panD摇瓶发酵可合成(5.0±0.2) g/L β-丙氨酸,体积生产强度达到(0.12±0.01) g/(L·h).该结果为发酵法合成β-丙氨酸奠定了基础.
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