title: Metabolic engineering of Escherichia coli for the production of hydroxy fatty acids from glucose.
abstract: BACKGROUND
  Hydroxy fatty acids (HFAs) are valuable chemicals for a broad variety of applications. However, commercial production of HFAs has not been established so far due to the lack of low cost routes for their synthesis. Although the microbial transformation pathway of HFAs was extensively studied decades ago, these attempts mainly focused on converting fatty acids or vegetable oils to their hydroxyl counterparts. The use of a wider range of feedstocks to produce HFAs would reduce the dependence on oil crops and be expected to cut down the manufacturing cost.
  
  
  RESULTS
  In this study, the industrially important microorganism Escherichia coli was engineered to produce HFAs directly from glucose. Through the coexpression of the acetyl-CoA carboxylase (ACCase) and the leadless acyl-CoA thioesterase ('TesA), and knockout of the endogenous acyl-CoA synthetase (FadD), an engineered E. coli strain was constructed to efficiently synthesize free fatty acids (FFAs). Under shake-flask conditions, 244.8 mg/L of FFAs were obtained by a 12 h induced culture. Then the fatty acid hydroxylase (CYP102A1) from Bacillus megaterium was introduced into this strain and high-level production of HFAs was achieved. The finally engineered strain BL21ΔfadD/pE-A1'tesA&pA-acc accumulated up to 58.7 mg/L of HFAs in the culture broth. About 24 % of the FFAs generated by the thioesterase were converted to HFAs. Fatty acid composition analysis showed that the HFAs mainly consisted of 9-hydroxydecanoic acid (9-OH-C10), 11-hydroxydodecanoic acid (11-OH-C12), 10-hydroxyhexadecanoic acid (10-OH-C16) and 12-hydroxyoctadecanoic acid (12-OH-C18). Fed-batch fermentation of this strain further increased the final titer of HFAs to 548 mg/L.
  
  
  CONCLUSIONS
  A robust HFA-producing strain was successfully constructed using glucose as the feedstock, which demonstrated a novel strategy for bioproduction of HFAs. The results of this work suggest that metabolically engineered E. coli has the potential to be a microbial cell factory for large-scale production of HFAs.
authors.affiliation: CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China. caoyj@qibebt.ac.cn.
authors.forename: Yujin
authors.initials: Y
authors.lastname: Cao
authors.affiliation: CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China. chengtao@qibebt.ac.cn.
authors.forename: Tao
authors.initials: T
authors.lastname: Cheng
authors.affiliation: CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China. zhaoguang@qibebt.ac.cn.
authors.forename: Guang
authors.initials: G
authors.lastname: Zhao
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA. wniu2@unl.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Niu
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA. jguo4@unl.edu.
authors.forename: Jiantao
authors.initials: J
authors.lastname: Guo
authors.affiliation: CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China. xianmo@qibebt.ac.cn.
authors.forename: Mo
authors.initials: M
authors.lastname: Xian
authors.affiliation: CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China. liuhuizhou@qibebt.ac.cn.
authors.forename: Huizhou
authors.initials: H
authors.lastname: Liu
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism*; D060847:Metabolic Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D011994:Recombinant Proteins; D000103:Acetyl-CoA Carboxylase; D005947:Glucose