title: Insights from the fungus Fusarium oxysporum point to high affinity glucose transporters as targets for enhancing ethanol production from lignocellulose.
abstract: Ethanol is the most-widely used biofuel in the world today. Lignocellulosic plant biomass derived from agricultural residue can be converted to ethanol via microbial bioprocessing. Fungi such as Fusarium oxysporum can simultaneously saccharify straw to sugars and ferment sugars to ethanol. But there are many bottlenecks that need to be overcome to increase the efficacy of microbial production of ethanol from straw, not least enhancement of the rate of fermentation of both hexose and pentose sugars. This research tested the hypothesis that the rate of sugar uptake by F. oxysporum would enhance the ethanol yields from lignocellulosic straw and that high affinity glucose transporters can enhance ethanol yields from this substrate. We characterized a novel hexose transporter (Hxt) from this fungus. The F. oxysporum Hxt represents a novel transporter with homology to yeast glucose signaling/transporter proteins Rgt2 and Snf3, but it lacks their C-terminal domain which is necessary for glucose signalling. Its expression level decreased with increasing glucose concentration in the medium and in a glucose uptake study the Km((glucose)) was 0.9 mM, which indicated that the protein is a high affinity glucose transporter. Post-translational gene silencing or over expression of the Hxt in F. oxysporum directly affected the glucose and xylose transport capacity and ethanol yielded by F. oxysporum from straw, glucose and xylose. Thus we conclude that this Hxt has the capacity to transport both C5 and C6 sugars and to enhance ethanol yields from lignocellulosic material. This study has confirmed that high affinity glucose transporters are ideal candidates for improving ethanol yields from lignocellulose because their activity and level of expression is high in low glucose concentrations, which is very common during the process of consolidated processing.
authors: Molecular Plant-Microbe Interactions Laboratory, School of Biology and Environmental Science, University College Dublin, Dublin, Ireland. shahin.ali@ucd.ie
authors: Shahin S
authors: SS
authors: Ali
authors: Brian
authors: B
authors: Nugent
authors: Ewen
authors: E
authors: Mullins
authors: Fiona M
authors: FM
authors: Doohan
mesh_terms: D056804:Biofuels; D050260:Carbohydrate Metabolism; D003001:Cloning, Molecular; D016000:Cluster Analysis; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005670:Fusarium / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008031:Lignin / Q000378:metabolism*; D014158:Transcription, Genetic; D014994:Xylose / Q000378:metabolism
chemical_list: D056804:Biofuels; D051246:Glucose Transport Proteins, Facilitative; C036909:lignocellulose; D000431:Ethanol; D008031:Lignin; D014994:Xylose; D005947:Glucose
references: Microbiol Mol Biol Rev. 1999 Sep;63(3):554-69
references: 10477308
references: Bioinformatics. 2007 Nov 1;23(21):2947-8
references: 17846036
references: Microbiology (Reading). 2007 Jun;153(Pt 6):1963-1973
references: 17526853
references: Appl Microbiol Biotechnol. 2007 Apr;74(5):1041-52
references: 17180689
references: Trends Biochem Sci. 1993 Jan;18(1):13-20
references: 8438231
references: Biosci Biotechnol Biochem. 2009 Jul;73(7):1671-3
references: 19584528
references: J Biol Chem. 1999 May 28;274(22):15350-9
references: 10336421
references: Appl Environ Microbiol. 1984 Jul;48(1):224-8
references: 16346591
references: J Bacteriol. 1994 Jun;176(12):3730-7
references: 8206851
references: Mol Microbiol. 1995 Apr;16(1):157-67
references: 7651133
references: EMBO J. 1998 May 1;17(9):2566-73
references: 9564039
references: Mol Cell Biol. 1995 Mar;15(3):1564-72
references: 7862149
references: Biochem Eng J. 2001 Jan;7(1):1-5
references: 11150790
references: Curr Opin Biotechnol. 2009 Jun;20(3):364-71
references: 19520566
references: J Bacteriol. 1993 Dec;175(23):7689-96
references: 8244939
references: Arch Microbiol. 1996 Nov;166(5):283-92
references: 8929273
references: Biotechnol Bioeng. 1982 Nov;24(11):2601-4
references: 18546229
references: Fungal Genet Biol. 2005 Apr;42(4):275-83
references: 15749047
references: Appl Environ Microbiol. 1987 Jun;53(6):1286-91
references: 3300550
references: EMBO J. 2006 Mar 22;25(6):1177-83
references: 16525509
references: Nucleic Acids Res. 2008 Jul 1;36(Web Server issue):W465-9
references: 18424797
references: Yeast. 2002 Jun 15;19(8):713-26
references: 12185841
references: Curr Opin Biotechnol. 2009 Jun;20(3):300-6
references: 19545992
references: Eukaryot Cell. 2003 Aug;2(4):708-17
references: 12912890
references: Enzyme Microb Technol. 2011 Mar 7;48(3):273-7
references: 22112911
references: Microbiology (Reading). 2002 Sep;148(Pt 9):2783-2788
references: 12213924
references: Theor Appl Genet. 2007 Mar;114(5):927-37
references: 17256175
references: J Biol Chem. 2000 Mar 24;275(12):8290-300
references: 10722658
references: Proc Natl Acad Sci U S A. 1996 Oct 29;93(22):12428-32
references: 8901598
references: Mol Cell Biol. 1996 Oct;16(10):5536-45
references: 8816466
references: Appl Environ Microbiol. 1990 Aug;56(8):2417-2420
references: 16348256
references: Mol Gen Genet. 1995 Nov 15;249(2):127-38
references: 7500933
references: Appl Environ Microbiol. 2004 Sep;70(9):5323-30
references: 15345416
references: Adv Biochem Eng Biotechnol. 1983;27:1-32
references: 6437152
references: FEBS Lett. 1999 Dec 31;464(3):123-8
references: 10618490
references: AMB Express. 2012 Mar 15;2(1):16
references: 22420408
references: Genetics. 1994 Aug;137(4):957-66
references: 7982576
references: Mol Cell Biol. 2003 Aug;23(15):5208-16
references: 12861007
references: Crit Rev Biotechnol. 1991;11(2):129-47
references: 1913845
references: Adv Microb Physiol. 1998;40:81-136
references: 9889977
references: Appl Microbiol Biotechnol. 2008 Sep;80(4):675-84
references: 18629494
references: Curr Opin Biotechnol. 2005 Oct;16(5):577-83
references: 16154338
references: Genetics. 1997 Jun;146(2):499-508
references: 9178001
references: Mol Cell Biol. 1993 Jan;13(1):638-48
references: 8417358
references: Funct Integr Genomics. 2008 Nov;8(4):421-7
references: 18592282