Engineering Escherichia coli for high‑yield geraniol production with biotransformation of geranyl acetate to geraniol under fed‑batch culture

Authors

Wei Liu, Chinese Academy of Sciences
Xin Xu, Chinese Academy of Sciences
Rubing Zhang, Chinese Academy of Sciences
Tao Cheng, Chinese Academy of Sciences
Yujin Cao, Chinese Academy of Sciences
Xiaoxiao Li, Chinese Academy of Sciences
Jiantao Guo, University of Nebraska-LincolnFollow
Huizhou Liu, Chinese Academy of SciencesFollow
Mo Xian, Chinese Academy of SciencesFollow

Document Type

Article

Date of this Version

2016

Citation

Liu et al. Biotechnol Biofuels (2016) 9:58 DOI 10.1186/s13068-016-0466-5

Erratum: Liu et al. Biotechnol Biofuels (2016) 9:131 DOI 10.1186/s13068-016-0539-5

Comments

© 2016 Liu et al. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License

An Erratum for this article is attached below.

Abstract

Background: Geraniol is an acyclic monoterpene alcohol, which exhibits good prospect as a gasoline alternative. Geraniol is naturally encountered in plants at low concentrations and an attractive target for microbial engineering. Geraniol has been heterologously produced in Escherichia coli, but the low titer hinders its industrial applications. Moreover, bioconversion of geraniol by E. coli remains largely unknown.

Results: Recombinant overexpression of Ocimum basilicum geraniol synthase, Abies grandis geranyl diphosphate synthase, and a heterotic mevalonate pathway in E. coli BL21 (DE3) enabled the production of up to 68.6 ± 3 mg/L geraniol in shake flasks. Initial fed-batch fermentation only increased geraniol production to 78.8 mg/L. To further improve the production yield, the fermentation conditions were optimized. Firstly, 81.4 % of volatile geraniol was lost during the first 5 h of fermentation in a solvent-free system. Hence, isopropyl myristate was added to the culture medium to form an aqueous-organic two-phase culture system, which effectively prevented volatilization of geraniol. Secondly, most of geraniol was eventually biotransformed into geranyl acetate by E. coli, thus decreasing geraniol production. For the first time, we revealed the role of acetylesterase (Aes, EC 3.1.1.6) from E. coli in hydrolyzing geranyl acetate to geraniol, and production of geraniol was successfully increased to 2.0 g/L under controlled fermentation conditions.

Conclusions: An efficient geraniol production platform was established by overexpressing several key pathway proteins in engineered E. coli strain combined with a controlled fermentation system. About 2.0 g/L geraniol was obtained using our controllable aqueous-organic two-phase fermentation system, which is the highest yield to date. In addition, the interconversion between geraniol and geranyl acetate by E. coli was first elucidated. This study provided a new and promising strategy for geraniol biosynthesis, which laid a basis for large-scale industrial application.