title: Engineering Escherichia coli for production of 4-hydroxymandelic acid using glucose-xylose mixture.
abstract: BACKGROUND
  4-Hydroxymandelic acid (4-HMA) is a valuable aromatic fine chemical and widely used for production of pharmaceuticals and food additives. 4-HMA is conventionally synthesized by chemical condensation of glyoxylic acid with excessive phenol, and the process is environmentally unfriendly. Microbial cell factory would be an attractive approach for 4-HMA production from renewable and sustainable resources.
  
  
  RESULTS
  In this study, a biosynthetic pathway for 4-HMA production was constructed by heterologously expressing the fully synthetic 4-hydroxymandelic acid synthase (shmaS) in our L-tyrosine-overproducing Escherichia coli BKT5. The expression level of shmaS was optimized to improve 4-HMA production by fine tuning of four promoters of different strength combined with three plasmids of different copy number. Furthermore, two genes aspC and tyrB in the competitive pathway were deleted to block the formation of byproduct to enhance 4-HMA biosynthesis. The final engineered E. coli strain HMA15 utilized glucose and xylose simultaneously and produced 15.8 g/L of 4-HMA by fed-batch fermentation in 60 h.
  
  
  CONCLUSIONS
  Metabolically engineered E. coli strain for 4-HMA production was designed and constructed, and efficiently co-fermented glucose and xylose, the major components in the hydrolysate mixture of agricultural biomass. Our research provided a promising biomanufacturing route to produce 4-HMA from lignocellulosic biomass.
authors.affiliation: Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.|Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China.|SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, China.
authors.forename: Fei-Fei
authors.initials: FF
authors.lastname: Li
authors.affiliation: Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.|Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China.|SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.|Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China.|SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, China.
authors.forename: Bing-Zhi
authors.initials: BZ
authors.lastname: Li
authors.affiliation: Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China. jianjunq@tju.edu.cn.|Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China. jianjunq@tju.edu.cn.|SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, China. jianjunq@tju.edu.cn.
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Qiao
authors.affiliation: Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China. grzhao@tju.edu.cn.|Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China. grzhao@tju.edu.cn.|SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, China. grzhao@tju.edu.cn.
authors.forename: Guang-Rong
authors.initials: GR
authors.lastname: Zhao
mesh_terms: D039903:Actinobacteria / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D019149:Bioreactors; D002851:Chromatography, High Pressure Liquid; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D008333:Mandelic Acids / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D060847:Metabolic Engineering; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014994:Xylose / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008333:Mandelic Acids; C014600:4-hydroxymandelic acid; D014994:Xylose; D005947:Glucose
keywords: 4-Hydroxymandelic acid; Co-utilization of glucose and xylose; Escherichia coli; Metabolic engineering; Synthetic biology