Abstract

N-butanol is an important chemical and can be naturally synthesized by Clostridium species; however, the poor n-butanol tolerance of Clostridium impedes the further improvement in titer. In this study, Lactobacillus brevis, which possesses a higher butanol tolerance, was selected as host for heterologous butanol production. The Clostridium acetobutylicum genes thl, hbd, and crt which encode thiolase, β-hydroxybutyryl-CoA dehydrogenase, and crotonase, and the Treponema denticola gene ter, which encodes trans-enoyl-CoA reductase were cloned into a single plasmid to express the butanol synthesis pathway in L. brevis. A titer of 40 mg/L n-butanol was initially achieved with plasmid pLY15-opt, in which all pathway genes are codon-optimized. A titer of 450 mg/L of n-butanol was then synthesized when ter was further overexpressed in this pathway. The role of metabolic flux was reinforced with pLY15, in which only the ter gene was codon-optimized, which greatly increased the n-butanol titer to 817 mg/L. Our strategy significantly improved n-butanol synthesis in L. brevis and the final titer is the highest achieved amongst butanol-tolerant lactic acid bacteria.

Graphic abstract

中文翻译：

---

通过thl，hbd，crt和ter的功能表达优化短乳杆菌中正丁醇的合成

摘要

Ñ丁醇是一种重要的化学和可以由天然合成梭菌物种; 但是，梭菌对正丁醇的耐受性差，阻碍了滴度的进一步提高。在这项研究中，具有较高丁醇耐受性的短乳杆菌被选作异源丁醇生产的宿主。所述丙酮丁醇梭菌基因THL，HBD，和CRT编码硫解酶，β羟丁酰辅酶A脱氢酶，巴豆酸酶和和梅毒螺旋齿垢基因之三，其编码反式将-烯酰辅酶A还原酶克隆到单个质粒中以表达短乳杆菌中的丁醇合成途径。最初使用质粒pLY15-opt获得了40 mg / L正丁醇的效价，其中所有途径基因均经过密码子优化。然后在该途径中进一步过表达ter时，合成了效价为450 mg / L的正丁醇。pLY15增强了代谢通量的作用，其中仅对ter基因进行了密码子优化，这使正丁醇效价大大提高至817 mg / L。我们的策略显着改善了短乳杆菌中正丁醇的合成，最终滴定度是耐丁醇乳酸菌中最高的。

图形摘要