title: Combined metabolic engineering of precursor and co-factor supply to increase α-santalene production by Saccharomyces cerevisiae.
abstract: BACKGROUND
  Sesquiterpenes are a class of natural products with a diverse range of attractive industrial proprieties. Due to economic difficulties of sesquiterpene production via extraction from plants or chemical synthesis there is interest in developing alternative and cost efficient bioprocesses. The hydrocarbon α-santalene is a precursor of sesquiterpenes with relevant commercial applications. Here, we construct an efficient Saccharomyces cerevisiae cell factory for α-santalene production.
  
  
  RESULTS
  A multistep metabolic engineering strategy targeted to increase precursor and cofactor supply was employed to manipulate the yeast metabolic network in order to redirect carbon toward the desired product. To do so, genetic modifications were introduced acting to optimize the farnesyl diphosphate branch point, modulate the mevalonate pathway, modify the ammonium assimilation pathway and enhance the activity of a transcriptional activator. The approach employed resulted in an overall α-santalene yield of a 0.0052 Cmmol (Cmmol glucose)(-1) corresponding to a 4-fold improvement over the reference strain. This strategy, combined with a specifically developed continuous fermentation process, led to a final α-santalene productivity of 0.036 Cmmol (g biomass)(-1) h(-1).
  
  
  CONCLUSIONS
  The results reported in this work illustrate how the combination of a metabolic engineering strategy with fermentation technology optimization can be used to obtain significant amounts of the high-value sesquiterpene α-santalene. This represents a starting point toward the construction of a yeast "sesquiterpene factory" and for the development of an economically viable bio-based process that has the potential to replace the current production methods.
authors.affiliation: Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
authors.forename: Gionata
authors.initials: G
authors.lastname: Scalcinati
authors.forename: Siavash
authors.initials: S
authors.lastname: Partow
authors.forename: Verena
authors.initials: V
authors.lastname: Siewers
authors.forename: Michel
authors.initials: M
authors.lastname: Schalk
authors.forename: Laurent
authors.initials: L
authors.lastname: Daviet
authors.forename: Jens
authors.initials: J
authors.lastname: Nielsen
mesh_terms: D005285:Fermentation; D060847:Metabolic Engineering; D008798:Mevalonic Acid / Q000378:metabolism; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011106:Polyisoprenyl Phosphates / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D012717:Sesquiterpenes / Q000737:chemistry / Q000378:metabolism
chemical_list: D011106:Polyisoprenyl Phosphates; D029701:Saccharomyces cerevisiae Proteins; D012717:Sesquiterpenes; C004808:farnesyl pyrophosphate; D008798:Mevalonic Acid