title: Hexokinase--A limiting factor in lipid production from fructose in Yarrowia lipolytica.
abstract: Microbial biolipid production has become an important part of making biofuel production economically feasible. Genetic engineering has been used to improve the ability of Yarrowia lipolytica, an oleaginous yeast, to produce lipids using glucose-based media. However, few studies have examined lipid accumulation by Y. lipolytica's ability to utilize other hexose sugars, and as of yet, the rate-limiting steps in this process are unidentified. In this study, we investigated the de novo accumulation of lipids by Y. lipolytica when grown in glucose, fructose, and sucrose. Three Y. lipolytica wild-type (WT) strains of varied origin differed significantly in their lipid production, growth, and fructose utilization. Hexokinase (ylHXK1p) activity partially explained these differences. Overexpression of the ylHXK1 gene led to increased hexokinase activity (6.5-12 times higher) in the mutants versus the WT strains; a pronounced reduction in cell filamentation in mutants grown in fructose-based media; and improved biomass production, particularly in the mutant whose parent had shown the lowest growth capacity in fructose (French strain W29). All mutants showed improved lipid yield and production when grown on fructose, although the effect was strain dependent (23-55% improvement). Finally, we overexpressed ylHXK1 in a highly modified strain of Y. lipolytica W29 engineered to optimize oil production. This modification was combined with Saccharomyces cerevisiae invertase gene expression to evaluate the resulting mutant's ability to produce lipids using cheap industrial substrates, namely sucrose (a major component of molasses). Sucrose turned out to be a better substrate than either of its building blocks, glucose or fructose. Over its 96 h of growth in the bioreactors, this highly modified strain produced 9.15 g L(-1) of lipids, yielding 0.262 g g(-1) of biomass.
authors.affiliation: INRA, AgroParisTech, UMR1319 Micalis, F-78350 Jouy-en-Josas, France; Department of Biotechnology and Food Microbiology, Wroclaw University of Environmental and Life Sciences, Chełmońskiego 37/41, 51-630 Wroclaw, Poland.
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Lazar
authors.affiliation: INRA, AgroParisTech, UMR1319 Micalis, F-78350 Jouy-en-Josas, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Dulermo
authors.affiliation: INRA, AgroParisTech, UMR1319 Micalis, F-78350 Jouy-en-Josas, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Neuvéglise
authors.affiliation: INRA, AgroParisTech, UMR1319 Micalis, F-78350 Jouy-en-Josas, France.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Crutz-Le Coq
authors.affiliation: INRA, AgroParisTech, UMR1319 Micalis, F-78350 Jouy-en-Josas, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Nicaud
mesh_terms: D050260:Carbohydrate Metabolism / Q000502:physiology*; D049109:Cell Proliferation / Q000502:physiology; D005632:Fructose / Q000378:metabolism*; D024861:Genetic Enhancement / Q000379:methods*; D006593:Hexokinase / Q000235:genetics*; D008055:Lipids / Q000096:biosynthesis* / Q000235:genetics; D025062:Yarrowia / Q000502:physiology*
chemical_list: D008055:Lipids; D005632:Fructose; D006593:Hexokinase
keywords: Fructose; Hexokinase; Lipid accumulation; Single-cell oil; Sucrose; Yeasts