title: Enhancement of medium-chain-length polyhydroxyalkanoates biosynthesis from glucose by metabolic engineering in Pseudomonas mendocina.
abstract: OBJECTIVE
  To enhance the biosynthesis of medium-chain-length polyhydroxyalkanoates (PHAMCL) from glucose in Pseudomonas mendocina NK-01, metabolic engineering strategies were used to block or enhance related pathways.
  
  
  RESULTS
  Pseudomonas mendocina NK-01 produces PHAMCL from glucose. Besides the alginate oligosaccharide biosynthetic pathway proved by our previous study, UDP-D-glucose and dTDP-L-rhamnose biosynthetic pathways were identified. These might compete for glucose with the PHAMCL biosynthesis. First, the alg operon, galU and rmlC gene were deleted one by one, resulting in NK-U-1(∆alg), NK-U-2 (∆alg∆galU), NK-U-3(alg∆galU∆rmlC). After fermentation for 36 h, the cell dry weight (CDW) and PHAMCL production of these strains were determined. Compared with NK-U: 1) NK-U-1 produced elevated CDW (from 3.19 ± 0.16 to 3.5 ± 0.11 g/l) and equal PHAMCL (from 0.78 ± 0.06 to 0.79 ± 0.07 g/l); 2) NK-U-2 produced more CDW (from 3.19 ± 0.16 to 3.55 ± 0.23 g/l) and PHAMCL (from 0.78 ± 0.06 to 1.05 ± 0.07 g/l); 3) CDW and PHAMCL dramatically decreased in NK-U-3 (1.53 ± 0.21 and 0.41 ± 0.09 g/l, respectively). Additionally, the phaG gene was overexpressed in strain NK-U-2. Although CDW of NK-U-2/phaG decreased to 1.29 ± 0.2 g/l, PHA titer (%CDW) significantly increased from 24.5 % up to 51.2 %.
  
  
  CONCLUSIONS
  The PHAMCL biosynthetic pathway was enhanced by blocking branched metabolic pathways in combination with overexpressing phaG gene.
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology for Ministry of Education, Nankai University, Tianjin, 300071, China. wyy2589@163.com.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology for Ministry of Education, Nankai University, Tianjin, 300071, China. 1099682316@qq.com.
authors.forename: Fengjie
authors.initials: F
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology for Ministry of Education, Nankai University, Tianjin, 300071, China. 812382037@qq.com.
authors.forename: Xu
authors.initials: X
authors.lastname: Fan
authors.affiliation: The Key Laboratory of Bioactive Materials, Ministry of Education, Nankai University, Tianjin, 300071, China. wangshufang@nankai.edu.cn.
authors.forename: Shufang
authors.initials: S
authors.lastname: Wang
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology for Ministry of Education, Nankai University, Tianjin, 300071, China. songcj@nankai.edu.cn.
authors.forename: Cunjiang
authors.initials: C
authors.lastname: Song
mesh_terms: D015870:Gene Expression; D055786:Gene Knockout Techniques; D005947:Glucose / Q000378:metabolism*; D060847:Metabolic Engineering / Q000379:methods*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis*; D044203:Pseudomonas mendocina / Q000235:genetics* / Q000378:metabolism*
chemical_list: D054813:Polyhydroxyalkanoates; D005947:Glucose
keywords: 3-Hydroxyacyl-ACP thioesterase (PhaG); Alginate oligosaccharides; Medium-chain-length polyhydroxyalkanoates; Polyhydroxyalkanoates; Pseudomonas mendocina; UDP-D-glucose; dTDP-L-rhamnose