Dataset Information

Comparative genomics of xylose-fermenting fungi for enhanced biofuel production.

ABSTRACT: Cellulosic biomass is an abundant and underused substrate for biofuel production. The inability of many microbes to metabolize the pentose sugars abundant within hemicellulose creates specific challenges for microbial biofuel production from cellulosic material. Although engineered strains of Saccharomyces cerevisiae can use the pentose xylose, the fermentative capacity pales in comparison with glucose, limiting the economic feasibility of industrial fermentations. To better understand xylose utilization for subsequent microbial engineering, we sequenced the genomes of two xylose-fermenting, beetle-associated fungi, Spathaspora passalidarum and Candida tenuis. To identify genes involved in xylose metabolism, we applied a comparative genomic approach across 14 Ascomycete genomes, mapping phenotypes and genotypes onto the fungal phylogeny, and measured genomic expression across five Hemiascomycete species with different xylose-consumption phenotypes. This approach implicated many genes and processes involved in xylose assimilation. Several of these genes significantly improved xylose utilization when engineered into S. cerevisiae, demonstrating the power of comparative methods in rapidly identifying genes for biomass conversion while reflecting on fungal ecology.

SUBMITTER: Wohlbach DJ

PROVIDER: S-EPMC3156214 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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Comparative genomics of xylose-fermenting fungi for enhanced biofuel production.

Wohlbach Dana J DJ Kuo Alan A Sato Trey K TK Potts Katlyn M KM Salamov Asaf A AA Labutti Kurt M KM Sun Hui H Clum Alicia A Pangilinan Jasmyn L JL Lindquist Erika A EA Lucas Susan S Lapidus Alla A Jin Mingjie M Gunawan Christa C Balan Venkatesh V Dale Bruce E BE Jeffries Thomas W TW Zinkel Robert R Barry Kerrie W KW Grigoriev Igor V IV Gasch Audrey P AP

Proceedings of the National Academy of Sciences of the United States of America 20110725 32

Cellulosic biomass is an abundant and underused substrate for biofuel production. The inability of many microbes to metabolize the pentose sugars abundant within hemicellulose creates specific challenges for microbial biofuel production from cellulosic material. Although engineered strains of Saccharomyces cerevisiae can use the pentose xylose, the fermentative capacity pales in comparison with glucose, limiting the economic feasibility of industrial fermentations. To better understand xylose ut ...[more]

PMID: 21788494

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Project description:Background:Engineered strains of Saccharomyces cerevisiae have significantly improved the prospects of biorefinery by improving the bioconversion yields in lignocellulosic bioethanol production and expanding the product profiles to include advanced biofuels and chemicals. However, the lignocellulosic biorefinery concept has not been fully applied using engineered strains in which either xylose utilization or advanced biofuel/chemical production pathways have been upgraded separately. Specifically, high-performance xylose-fermenting strains have rarely been employed as advanced biofuel and chemical production platforms and require further engineering to expand their product profiles. Results:In this study, we refactored a high-performance xylose-fermenting S. cerevisiae that could potentially serve as a platform strain for advanced biofuels and biochemical production. Through combinatorial CRISPR-Cas9-mediated rational and evolutionary engineering, we obtained a newly refactored isomerase-based xylose-fermenting strain, XUSE, that demonstrated efficient conversion of xylose into ethanol with a high yield of 0.43 g/g. In addition, XUSE exhibited the simultaneous fermentation of glucose and xylose with negligible glucose inhibition, indicating the potential of this isomerase-based xylose-utilizing strain for lignocellulosic biorefinery. The genomic and transcriptomic analysis of XUSE revealed beneficial mutations and changes in gene expression that are responsible for the enhanced xylose fermentation performance of XUSE. Conclusions:In this study, we developed a high-performance xylose-fermenting S. cerevisiae strain, XUSE, with high ethanol yield and negligible glucose inhibition. Understanding the genomic and transcriptomic characteristics of XUSE revealed isomerase-based engineering strategies for improved xylose fermentation in S. cerevisiae. With high xylose fermentation performance and room for further engineering, XUSE could serve as a promising platform strain for lignocellulosic biorefinery.

Project description:Bacteria was grown at 30C in 3 different conditions, i.e. SYN (syngas and minimal medium- ATCC no 1789), AC (0.3% acetate in minimal medium- ATCC no 1789) and TSB (tryptic soy broth). After harvesting by centrifugation, O. carboxidovorans pellets (1g) were lysed in 100 mM Tris-Cl pH 8.0, 2% Triton X-100, 2.6 mg/ml sodium azide, 8 mM PMSF by sonication on ice (4 pulses of 15 s duration each). For each condition of growth 4 samples (1g pellets) were separately treated (i.e. lysed and processed further). The supernatants were treated with 50% cold TCA, and the precipitated protein washed with acetone. The pellets were resuspended in solubilization buffer (7M urea, 20 mM tris-Cl, pH 8.0, 5 mM EDTA, 5 mM MgCl2, 4% CHAPS), and protein concentration was determined using the Plus One 2-D Quant Kit (Amersham) following the manufacturers instructions. Protein samples from each treatment were stored at -80 C. One hundred micrograms of each protein sample was resuspended in 0.1 M ammonium bicarbonate, 5% HPLC grade ACN, reduced in 5 mM DTT (65 C, 5 min), alkylated in 10 mM iodoacetamide (30 C, 30 min), and then trypsin digested until there was no visible pellet (1:50 w/w 37 C, 16 h). Peptides were desalted using a peptide microtrap (Michrom BioResources, Auburn, CA) and eluted using a 0.1% TFA, 95% ACN solution. Desalted peptides were dried in a vacuum centrifuge and resuspended in 20 ?l of 0.1% formic acid. Peptides were separated by strong cation exchange (SCX) liquid chromatography (LC) followed by reverse phase (RP) LC coupled directly in line with electrospray ionization (ESI) tandem mass spectrometry (MS/MS). 2DLC ESI MS/MS was done exactly as described (1). All searches were done using TurboSEQUEST (Bioworks Browser 3.2; Thermo Electron). Mass spectra and tandem mass spectra were searched against all annotated proteins from the strain OM5 including all the annotated plasmid-encoded proteins. Cysteine carbamidomethylation and methionine oxidation (single and double) were included in the search strategy. We used the reverse database functionality in Bioworks 3.2 and searched MS2 data against a reversed OM5 database using identical search criteria.

Dataset Information

Comparative genomics of xylose-fermenting fungi for enhanced biofuel production.

Publications

Comparative genomics of xylose-fermenting fungi for enhanced biofuel production.

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