Biosynthesis of Fatty Alcohols in Engineered Microbial Cell Factories: Advances and Limitations.

Anagha Krishnan,Bonnie A Mcneil,David T Stuart

doi:10.3389/fbioe.2020.610936

Anagha Krishnan, Bonnie A Mcneil + Show 1 more

Open Access

https://doi.org/10.3389/fbioe.2020.610936

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Abstract

Concerns about climate change and environmental destruction have led to interest in technologies that can replace fossil fuels and petrochemicals with compounds derived from sustainable sources that have lower environmental impact. Fatty alcohols produced by chemical synthesis from ethylene or by chemical conversion of plant oils have a large range of industrial applications. These chemicals can be synthesized through biological routes but their free forms are produced in trace amounts naturally. This review focuses on how genetic engineering of endogenous fatty acid metabolism and heterologous expression of fatty alcohol producing enzymes have come together resulting in the current state of the field for production of fatty alcohols by microbial cell factories. We provide an overview of endogenous fatty acid synthesis, enzymatic methods of conversion to fatty alcohols and review the research to date on microbial fatty alcohol production. The primary focus is on work performed in the model microorganisms, Escherichia coli and Saccharomyces cerevisiae but advances made with cyanobacteria and oleaginous yeasts are also considered. The limitations to production of fatty alcohols by microbial cell factories are detailed along with consideration to potential research directions that may aid in achieving viable commercial scale production of fatty alcohols from renewable feedstock.

Highlights

The use of microbial cells for the production of oleochemicals, of single cell oil (SCO), has been of interest since the second half of the twentieth century as an alternative to traditional petrochemical production
As flux through the fatty acid synthesis pathway is relatively low, increasing the availability of acyl-CoA substrates has been a major focus of metabolic engineering for fatty alcohol production in S. cerevisiae (Figure 4)
For the production of medium chain length fatty alcohols TaFAR1 was expressed with a peroxisomal signal sequence in conjunction with overexpression of ACC1 and PEX7, resulting in a strain producing over 1.3 g L−1 of medium and long chain fatty alcohols in fed-batch culture (Sheng et al, 2016)

Summary

Introduction

The use of microbial cells for the production of oleochemicals, of single cell oil (SCO), has been of interest since the second half of the twentieth century as an alternative to traditional petrochemical production. Feng et al (2015) co-expressed ACL1 and ACL2, from either A. thaliana or Y. lipolytica in a fatty alcohol producing S. cerevisiae strain resulting in a 55 and 136% increase in 1-hexadecanol production, respectively achieving up to 330 mg L−1 titer in shake flask culture (Feng et al, 2015).

Results

Conclusion