title: Utilization of xylose by engineered strains ofAshbya gossypiifor the production of microbial oils.
abstract: BACKGROUND
  Ashbya gossypiiis a filamentous fungus that is currently exploited for the industrial production of riboflavin. The utilization ofA. gossypiias a microbial biocatalyst is further supported by its ability to grow in low-cost feedstocks, inexpensive downstream processing and the availability of an ease to use molecular toolbox for genetic and genomic modifications. Consequently,A. gossypiihas been also introduced as an ideal biotechnological chassis for the production of inosine, folic acid, and microbial oils. However,A. gossypiicannot use xylose, the most common pentose in hydrolysates of plant biomass.
  
  
  RESULTS
  In this work, we aimed at designingA. gossypiistrains able to utilize xylose as the carbon source for the production of biolipids. An endogenous xylose utilization pathway was identified and overexpressed, resulting in anA. gossypiixylose-metabolizing strain showing prominent conversion rates of xylose to xylitol (up to 97% after 48 h). In addition, metabolic flux channeling from xylulose-5-phosphate to acetyl-CoA, using aheterologous phosphoketolase pathway, increased the lipid content in the xylose-metabolizing strain a 54% over the parental strain growing in glucose-based media. This increase raised to 69% when lipid accumulation was further boosted by blocking the beta-oxidation pathway.
  
  
  CONCLUSIONS
  Ashbya gossypiihas been engineered for the utilization of xylose. We present here a proof-of-concept study for the production of microbial oils from xylose inA. gossypii, thus introducing a novel biocatalyst with very promising properties in developing consolidated bioprocessing to produce fine chemicals and biofuels from xylose-rich hydrolysates of plant biomass.
authors.affiliation: Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Díaz-Fernández
authors.affiliation: Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Lozano-Martínez
authors.affiliation: Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain.
authors.forename: Rubén M
authors.initials: RM
authors.lastname: Buey
authors.affiliation: Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Revuelta
authors.affiliation: Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Jiménez
keywords: Ashbya gossypii; Lipids; Metabolic engineering; Xylitol; Xylose