title: Detoxification of 5-hydroxymethylfurfural by the Pleurotus ostreatus lignolytic enzymes aryl alcohol oxidase and dehydrogenase.
abstract: BACKGROUND
  Current large-scale pretreatment processes for lignocellulosic biomass are generally accompanied by the formation of toxic degradation products, such as 5-hydroxymethylfurfural (HMF), which inhibit cellulolytic enzymes and fermentation by ethanol-producing yeast. Overcoming these toxic effects is a key technical barrier in the biochemical conversion of plant biomass to biofuels. Pleurotus ostreatus, a white-rot fungus, can efficiently degrade lignocellulose. In this study, we analyzed the ability of P. ostreatus to tolerate and metabolize HMF and investigated relevant molecular pathways associated with these processes.
  
  
  RESULTS
  P. ostreatus was capable to metabolize and detoxify HMF 30 mM within 48 h, converting it into 2,5-bis-hydroxymethylfuran (HMF alcohol) and 2,5-furandicarboxylic acid (FDCA), which subsequently allowed the normal yeast growth in amended media. We show that two enzymes groups, which belong to the ligninolytic system, aryl-alcohol oxidases and a dehydrogenase, are involved in this process. HMF induced the transcription and production of these enzymes and was accompanied by an increase in activity levels. We also demonstrate that following the induction of these enzymes, HMF could be metabolized in vitro.
  
  
  CONCLUSIONS
  Aryl-alcohol oxidase and dehydrogenase gene family members are part of the transcriptional and subsequent translational response to HMF exposure in P. ostreatus and are involved in HMF transformation. Based on our data, we propose that these enzymatic capacities of P. ostreatus either be integrated in biomass pretreatment or the genes encoding these enzymes may function to detoxify HMF via heterologous expression in fermentation organisms, such as Saccharomyces cerevisiae.
authors.affiliation: Department of Plant Pathology and Microbiology, The R.H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot, 76100 Israel.
authors.forename: Daria
authors.initials: D
authors.lastname: Feldman
authors.affiliation: Department of Plant and Microbial Biology, University of California at Berkeley, 111 Koshland Hall, Berkeley, California 94720 USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Kowbel
authors.affiliation: Department of Plant and Microbial Biology, University of California at Berkeley, 111 Koshland Hall, Berkeley, California 94720 USA.
authors.forename: N Louise
authors.initials: NL
authors.lastname: Glass
authors.affiliation: Department of Plant Pathology and Microbiology, The R.H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot, 76100 Israel.
authors.forename: Oded
authors.initials: O
authors.lastname: Yarden
authors.affiliation: Department of Plant Pathology and Microbiology, The R.H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot, 76100 Israel.
authors.forename: Yitzhak
authors.initials: Y
authors.lastname: Hadar
keywords: 5-hydroxymethylfurfural (HMF); Aryl-alcohol dehydrogenase; Aryl-alcohol oxidase; Pleurotus ostreatus