产L-肉碱的大肠杆菌基因工程改造及生物转化

Genetically engineering Escherichia coli strain and its optimized bioconversion for L-carnitine production

摘要: L-肉碱在脂肪代谢中起重要的作用,本文构建了T7启动子控制下的过表达质粒p ET28a-cai BCD和p ACYCD-cai F-cai T,并将其转入大肠杆菌BL21（DE3）（简写DE3）中,得到基因工程菌BL21（DE3）/cai BCD+cai F+cai T（简写DE3/BCD+F+T）。将此菌株接种到生长培养基中,并用终浓度为1 mmol/L的IPTG（异丙基硫代半乳糖苷）诱导培养,然后收集菌体细胞加入到含有巴豆甜菜碱盐酸盐的转化液中进行转化。结果显示,IPTG诱导4 h比诱导10 h后转化得到的L-肉碱量要高,转入了过表达质粒的工程菌DE3/BCD+F+T（7.244 g/L）比野生型DE3（0.5 g/L）提高了15倍。该巴豆甜菜碱盐酸盐转化生成L-肉碱的反应在2 h后基本达到稳定。

Abstract: L-carnitine plays an important role in fatty acids metabolism.Here a recombinant L-carnitine production strain had been constructed carrying two expression plasmids, p ET28a-cai BCD and p ACYCD-cai F-cai T, under the control of T7 promoter.This strain was genetically stable and can programmably produce L-carnitine with IPTG induction.1 mmol/L IPTG was added to induce enzymes expression, after 4 hours induction, cells were collected for the bioconversion of crotonobetaine to L-carnitine.Compared with wild-type strain, the conversion amount of recombinant strain was increased by 15 times. And it took about two hours for the conversion of crotonobetaine to L-carnitine.