title: Metabolic engineering of Escherichia coli for the production of cinnamaldehyde.
abstract: BACKGROUND
  Plant parasitic nematodes are harmful to agricultural crops and plants, and may cause severe yield losses. Cinnamaldehyde, a volatile, yellow liquid commonly used as a flavoring or food additive, is increasingly becoming a popular natural nematicide because of its high nematicidal activity and, there is a high demand for the development of a biological platform to produce cinnamaldehyde.
  
  
  RESULTS
  We engineered Escherichia coli as an eco-friendly biological platform for the production of cinnamaldehyde. In E. coli, cinnamaldehyde can be synthesized from intracellular L-phenylalanine, which requires the activities of three enzymes: phenylalanine-ammonia lyase (PAL), 4-coumarate:CoA ligase (4CL), and cinnamoyl-CoA reductase (CCR). For the efficient production of cinnamaldehyde in E. coli, we first examined the activities of enzymes from different sources and a gene expression system for the selected enzymes was constructed. Next, the metabolic pathway for L-phenylalanine biosynthesis was engineered to increase the intracellular pool of L-phenylalanine, which is a main precursor of cinnamaldehyde. Finally, we tried to produce cinnamaldehyde with the engineered E. coli. According to this result, cinnamaldehyde production as high as 75 mg/L could be achieved, which was about 35-fold higher compared with that in the parental E. coli W3110 harboring a plasmid for cinnamaldehyde biosynthesis. We also confirmed that cinnamaldehyde produced by our engineered E. coli had a nematicidal activity similar to the activity of commercial cinnamaldehyde by nematicidal assays against Bursaphelenchus xylophilus.
  
  
  CONCLUSIONS
  As a potential natural pesticide, cinnamaldehyde was successfully produced in E. coli by construction of the biosynthesis pathway and, its production titer was also significantly increased by engineering the metabolic pathway of L-phenylalanine.
authors.affiliation: Department of Chemical and Biomolecular Engineering (BK21 Plus Program), KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea. hyunbae@kaist.ac.kr.
authors.forename: Hyun Bae
authors.initials: HB
authors.lastname: Bang
authors.affiliation: Department of Chemical and Biomolecular Engineering (BK21 Plus Program), KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea. yoonhuk30@kaist.ac.kr.
authors.forename: Yoon Hyeok
authors.initials: YH
authors.lastname: Lee
authors.affiliation: Department of Biological Science, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea. sunkim@kaist.ac.kr.
authors.forename: Sun Chang
authors.initials: SC
authors.lastname: Kim
authors.affiliation: Department of Food Science and Technology, Chungnam National University, 99 Daehak-ro, Daejeon, 17045, Republic of Korea. kchsung@cnu.ac.kr.
authors.forename: Chang Keun
authors.initials: CK
authors.lastname: Sung
authors.affiliation: Department of Chemical and Biomolecular Engineering (BK21 Plus Program), KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea. kjjeong@kaist.ac.kr.|Institute for the BioCentury, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea. kjjeong@kaist.ac.kr.
authors.forename: Ki Jun
authors.initials: KJ
authors.lastname: Jeong
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D060847:Metabolic Engineering / Q000379:methods*; D010957:Plasmids / Q000235:genetics
chemical_list: D000171:Acrolein; C012843:cinnamaldehyde