Abstract
BackgroundCurrent 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.ResultsP. 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.ConclusionsAryl-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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0244-9) contains supplementary material, which is available to authorized users.
Highlights
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
HMF is bio-converted by P. ostreatus In order to explore the effect of HMF on P. ostreatus, we first examined the tolerance of the fungus toward the grown for 8 or 24 h in the presence of HMF, growth of the culture was elevated to 50% and to 85%, respectively
These results are in agreement with the level of transformation of HMF by P. ostreatus at those time points and suggest that the fungus has the potential to be used for reducing the toxic effects of HMF and may serve as a safe pretreatment amendment
Summary
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. In spite of the necessity for pretreatment of plant biomass, it can be a rate-limiting step in fermentation due to the production of inhibitory compounds, furans, such as 5-hydroxymethylfurfural (HMF) and furfural and other phenolic compounds [3,4,5]. In vitro experiments and crude cell extract measurements showed that HMF directly inhibited alcohol dehydrogenase, pyruvate
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
