Modular design of metabolic network for robust production of n-butanol from galactose–glucose mixtures

Biotechnology for Biofuels

Hyun Gyu Lim²  Jae Hyung Lim¹  Gyoo Yeol Jung¹ 

[1] School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Pohang 37673, Gyeongbuk, Korea

[2] Department of Chemical Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Pohang 37673, Gyeongbuk, Korea

关键词: Butanol;    Redox balance;    Galactose;    Synthetic biology;    Metabolic engineering;   

Others  :  1228143
DOI  :  10.1186/s13068-015-0327-7

 received in 2015-05-11, accepted in 2015-08-25,  发布年份 2015

【 摘 要 】

Background

Refactoring microorganisms for efficient production of advanced biofuel such as n-butanol from a mixture of sugars in the cheap feedstock is a prerequisite to achieve economic feasibility in biorefinery. However, production of biofuel from inedible and cheap feedstock is highly challenging due to the slower utilization of biomass-driven sugars, arising from complex assimilation pathway, difficulties in amplification of biosynthetic pathways for heterologous metabolite, and redox imbalance caused by consuming intracellular reducing power to produce quite reduced biofuel. Even with these problems, the microorganisms should show robust production of biofuel to obtain industrial feasibility. Thus, refactoring microorganisms for efficient conversion is highly desirable in biofuel production.

Results

In this study, we engineered robust Escherichia coli to accomplish high production of n-butanol from galactose–glucose mixtures via the design of modular pathway, an efficient and systematic way, to reconstruct the entire metabolic pathway with many target genes. Three modular pathways designed using the predictable genetic elements were assembled for efficient galactose utilization, n-butanol production, and redox re-balancing to robustly produce n-butanol from a sugar mixture of galactose and glucose. Specifically, the engineered strain showed dramatically increased n-butanol production (3.3-fold increased to 6.2 g/L after 48-h fermentation) compared to the parental strain (1.9 g/L) in galactose-supplemented medium. Moreover, fermentation with mixtures of galactose and glucose at various ratios from 2:1 to 1:2 confirmed that our engineered strain was able to robustly produce n-butanol regardless of sugar composition with simultaneous utilization of galactose and glucose.

Conclusions

Collectively, modular pathway engineering of metabolic network can be an effective approach in strain development for optimal biofuel production with cost-effective fermentable sugars. To the best of our knowledge, this study demonstrated the first and highest n-butanol production from galactose in E. coli. Moreover, robust production of n-butanol with sugar mixtures with variable composition would facilitate the economic feasibility of the microbial process using a mixture of sugars from cheap biomass in the near future.

【 授权许可】

   
2015 Lim et al.

【 图 表 】

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