1. Production of free monounsaturated fatty acids by metabolically engineered Escherichia coli
- Author
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Wei Liu, Xin Xu, Haibo Zhang, Jiming Wang, Mo Xian, and Yujin Cao
- Subjects
Coenzyme A ,Management, Monitoring, Policy and Law ,Applied Microbiology and Biotechnology ,Metabolic engineering ,acyl-CoA synthetase ,chemistry.chemical_compound ,chemistry.chemical_classification ,biology ,Renewable Energy, Sustainability and the Environment ,Research ,Fatty acid desaturase ,Acetyl-CoA carboxylase ,food and beverages ,Fatty acid ,Thioesterase ,Malonyl Coenzyme A ,acetyl-CoA carboxylase ,General Energy ,Biochemistry ,chemistry ,biology.protein ,lipids (amino acids, peptides, and proteins) ,Fermentation ,Free monounsaturated fatty acids ,Biotechnology ,Polyunsaturated fatty acid - Abstract
Background Monounsaturated fatty acids (MUFAs) are the best components for biodiesel when considering the low temperature fluidity and oxidative stability. However, biodiesel derived from vegetable oils or microbial lipids always consists of significant amounts of polyunsaturated and saturated fatty acids (SFAs) alkyl esters, which hampers its practical applications. Therefore, the fatty acid composition should be modified to increase MUFA contents as well as enhancing oil and lipid production. Results The model microorganism Escherichia coli was engineered to produce free MUFAs. The fatty acyl-ACP thioesterase (AtFatA) and fatty acid desaturase (SSI2) from Arabidopsis thaliana were heterologously expressed in E. coli BL21 star(DE3) to specifically release free unsaturated fatty acids (UFAs) and convert SFAs to UFAs. In addition, the endogenous fadD gene (encoding acyl-CoA synthetase) was disrupted to block fatty acid catabolism while the native acetyl-CoA carboxylase (ACCase) was overexpressed to increase the malonyl coenzyme A (malonyl-CoA) pool and boost fatty acid biosynthesis. The finally engineered strain BL21ΔfadD/pE-AtFatAssi2&pA-acc produced 82.6 mg/L free fatty acids (FFAs) under shake-flask conditions and FFAs yield on glucose reached about 3.3% of the theoretical yield. Two types of MUFAs, palmitoleate (16:1Δ9) and cis-vaccenate (18:1Δ11) made up more than 75% of the FFA profiles. Fed-batch fermentation of this strain further enhanced FFAs production to a titer of 1.27 g/L without affecting fatty acid compositions. Conclusions This study demonstrated the possibility to regulate fatty acid composition by using metabolic engineering approaches. FFAs produced by the recombinant E. coli strain consisted of high-level MUFAs and biodiesel manufactured from these fatty acids would be more suitable for current diesel engines.
- Published
- 2014