title: Engineering Escherichia coli to convert acetic acid to β-caryophyllene.
abstract: BACKGROUND
  Under aerobic conditions, acetic acid is the major byproduct produced by E. coli during the fermentation. And acetic acid is detrimental to cell growth as it destroys transmembrane pH gradients. Hence, how to reduce the production of acetic acid and how to utilize it as a feedstock are of intriguing interest. In this study, we provided an evidence to produce β-caryophyllene by the engineered E. coli using acetic acid as the only carbon source.
  
  
  RESULTS
  Firstly, to construct the robust acetate-utilizing strain, acetyl-CoA synthases from three different sources were introduced and screened in the E. coli. Secondly, to establish the engineered strains converting acetic acid to β-caryophyllene, acetyl-CoA synthase (ACS), β-caryophyllene synthase (QHS1) and geranyl diphosphate synthase (GPPS2) were co-expressed in the E. coli cells. Thirdly, to further enhance β-caryophyllene production from acetic acid, the heterologous MVA pathway was introduced into the cells. What's more, acetoacetyl-CoA synthase (AACS) was also expressed in the cells to increase the precursor acetoacetyl-CoA and accordingly resulted in the increase of β-caryophyllene. The final genetically modified strain, YJM67, could accumulate the production of biomass and β-caryophyllene up to 12.6 and 1.05 g/L during 72 h, respectively, with a specific productivity of 1.15 mg h(-1) g(-1) dry cells, and the conversion efficiency of acetic acid to β-caryophyllene (gram to gram) reached 2.1%. The yield of β-caryophyllene on acetic acid of this strain also reached approximately 5.6% of the theoretical yield.
  
  
  CONCLUSIONS
  In the present study, a novel biosynthetic pathway for β-caryophyllene has been investigated by means of conversion of acetic acid to β-caryophyllene using an engineered Escherichia coli. This was the first successful attempt in β-caryophyllene production by E. coli using acetic acid as the only carbon source. Therefore, we have provided a new metabolic engineering tool for β-caryophyllene synthesis.
authors.affiliation: Key Lab of Plant Biotechnology in Universities of Shandong Province; College of Life Sciences, Qingdao Agricultural University, Qingdao, 266109, China. yjming888@126.com.|Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, No.700 Changcheng Road, Chengyang District, Qingdao, 266109, China. yjming888@126.com.
authors.forename: Jianming
authors.initials: J
authors.lastname: Yang
authors.affiliation: Foreign Languages School, Qingdao Agricultural University, Qingdao, 266109, China.
authors.forename: Qingjuan
authors.initials: Q
authors.lastname: Nie
mesh_terms: D019342:Acetic Acid / Q000378:metabolism*; D000105:Acetyl Coenzyme A / Q000235:genetics / Q000378:metabolism; D019306:Artemisia / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D053898:Biosynthetic Pathways / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D005818:Genetic Engineering; D051228:Geranyltranstransferase / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D000081223:Polycyclic Sesquiterpenes; D012717:Sesquiterpenes / Q000378:metabolism*; D013302:Streptomyces / Q000201:enzymology / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D000081223:Polycyclic Sesquiterpenes; D012717:Sesquiterpenes; D000105:Acetyl Coenzyme A; C024714:caryophyllene; D051228:Geranyltranstransferase; D019342:Acetic Acid
keywords: Acetic acid; E. coli; MVA pathway; β-caryophyllene