克雷伯氏菌乙醛脱氢酶基因过表达及产乙醇发酵工艺优化

Overexpression of acetaldehyde dehydrogenase gene in Klebsiella sp. and optimization for fermentation process of ethanol production

为获得高效产乙醇的基因重组菌,该研究从克雷伯氏菌(Klebsiella sp.)WL1316中克隆乙醛脱氢酶aldh基因,进行同源过表达,考察其利用木质纤维素水解液中葡萄糖和木糖的能力,并以乙醇含量为响应值,通过单因素试验及响应面试验对其发酵稻草水解液产乙醇的工艺条件进行优化。结果表明,成功构建了同源过表达aldh基因的重组菌株aldh-pET-28a-Klebsiella sp.WL1316,其保持了野生菌株Klebsiella sp.WL1316利用木质纤维素水解液中葡萄糖和木糖的特性,且发酵稻草水解液产乙醇的最优发酵工艺为发酵时间60 h,异丙基硫代半乳糖苷(IPTG)诱导浓度1.5 mmol/L,发酵培养基初始pH值7.3,初始还原糖含量59 g/L。在此最优工艺条件下,重组菌株的乙醇含量为(5.39±0.51)g/L,是野生菌株[(3.67±0.32)g/L]的1.47倍,表明aldh基因的过表达促进了乙醇产量的提高。

In order to obtain a gene recombinant strain with efficient ethanol production,the aldh gene of acetaldehyde dehydrogenase was cloned from Klebsiella sp.WL1316 and homologous overexpression was carried out,and its ability to utilize glucose and xylose in lignocellulosic hydrolysate was investigated.Using the ethanol content as response value,the process conditions for ethanol production from rice straw hydrolysate fermented by the strain were optimized by single factor tests and response surface tests.The results showed that the recombinant strain aldh-pET-28a-Klebsiella sp.WL1316 that could homologously overexpress aldh gene was successfully constructed,which maintained the characteristics of utilizing glucose and xylose in lignocellulosic hydrolysate by wild strain Klebsiella sp.WL1316.The optimal fermentation process for ethanol production from rice straw hydrolysate was as follows:fermentation time 60 h,isopropyl-β-D-thiogalactoside(IPTG)induced concentration 1.5 mmol/L,initial pH of fermentation medium 7.3,and initial reducing sugar content 59 g/L.Under the optimal process conditions,the ethanol content of the recombinant strain was(5.39±0.51)g/L,which was 1.47 times that of the wild strain[(3.67±0.32)g/L],indicating that the overexpression of aldh gene promoted the increase of ethanol production.