title: Interactive forces between lignin and cellulase as determined by atomic force microscopy.
abstract: BACKGROUND
  Lignin is a complex polymer which inhibits the enzymatic conversion of cellulose to glucose in lignocellulose biomass for biofuel production. Cellulase enzymes irreversibly bind to lignin, deactivating the enzyme and lowering the overall activity of the hydrolyzing reaction solution. Within this study, atomic force microscopy (AFM) is used to compare the adhesion forces between cellulase and lignin with the forces between cellulase and cellulose, and to study the moiety groups involved in binding of cellulase to lignin.
  
  
  RESULTS
  Trichoderma reesei, ATCC 26921, a commercial cellulase system, was immobilized onto silicon wafers and used as a substrate to measure forces involved in cellulase non-productive binding to lignin. Attraction forces between cellulase and lignin, and between cellulase and cellulose were compared using kraft lignin- and hydroxypropyl cellulose-coated tips with the immobilized cellulase substrate. The measured adhesion forces between kraft lignin and cellulase were on average 45% higher than forces between hydroxypropyl cellulose and cellulase. Specialized AFM tips with hydrophobic, -OH, and -COOH chemical characteristics were used with immobilized cellulase to represent hydrophobic, H-bonding, and charge-charge interactions, respectively. Forces between hydrophobic tips and cellulase were on average 43% and 13% higher than forces between cellulase with tips exhibiting OH and COOH groups, respectively. A strong attractive force during the AFM tip approach to the immobilized cellulase was observed with the hydrophobic tip.
  
  
  CONCLUSIONS
  This work shows that there is a greater overall attraction between kraft lignin and cellulase than between hydroxypropyl cellulose and cellulase, which may have implications during the enzymatic reaction process. Furthermore, hydrophobic interactions appear to be the dominating attraction force in cellulase binding to lignin, while a number of other interactions may establish the irreversible binding.
authors.affiliation: College of Light Industry and Food Engineering, Guangxi University, 100 University Road, Nanning, Guangxi Province 530004, PR China.
authors.forename: Chengrong
authors.initials: C
authors.lastname: Qin
authors.affiliation: Department of Chemical Engineering, University of New Brunswick, 2 Garland Court, Incutech Complex, Fredericton, NB E3B 5A3, Canada.
authors.forename: Kimberley
authors.initials: K
authors.lastname: Clarke
authors.affiliation: Department of Chemical Engineering, University of New Brunswick, 2 Garland Court, Incutech Complex, Fredericton, NB E3B 5A3, Canada.
authors.forename: Kecheng
authors.initials: K
authors.lastname: Li
keywords: Atomic force microscopy; Cellulase; Enzymatic hydrolysis; Lignin; Non-productive binding
references.citation: Phys Chem Chem Phys. 2013 May 7;15(17):6508-15
references.pmid: 23532050
references.citation: Prog Biophys Mol Biol. 1997;67(2-3):183-216
references.pmid: 9446935
references.citation: Biotechnol Bioeng. 1988 Apr 5;31(5):447-56
references.pmid: 18584630
references.citation: Langmuir. 2009 Feb 3;25(3):1582-7
references.pmid: 19170645
references.citation: Biotechnol Bioeng. 2012 Aug;109(8):1965-75
references.pmid: 22383340
references.citation: Adv Biochem Eng Biotechnol. 2007;108:67-93
references.pmid: 17530205
references.citation: Biotechnol Prog. 2012 Nov-Dec;28(6):1389-99
references.pmid: 22887935
references.citation: Appl Biochem Biotechnol. 2002 Spring;98-100:641-54
references.pmid: 12018289
references.citation: Phys Rev Lett. 1986 Mar 3;56(9):930-933
references.pmid: 10033323
references.citation: Biotechnol Bioeng. 2012 Feb;109(2):434-43
references.pmid: 22006641
references.citation: Appl Biochem Biotechnol. 2005 Spring;121-124:163-70
references.pmid: 15917596
references.citation: J Phys Chem B. 2012 Aug 23;116(33):9949-56
references.pmid: 22849362
references.citation: Enzyme Microb Technol. 2000 Nov 15;27(9):664-671
references.pmid: 11064048
references.citation: Macromolecules. 1976 Mar-Apr;9(2):273-8
references.pmid: 1263576
references.citation: J Agric Food Chem. 2009 Sep 9;57(17):7771-8
references.pmid: 19722706
references.citation: Int Microbiol. 2002 Jun;5(2):53-63
references.pmid: 12180781
references.citation: Appl Biochem Biotechnol. 2008 Mar;146(1-3):231-48
references.pmid: 18421601
references.citation: J Bacteriol. 1993 Sep;175(18):5762-8
references.pmid: 8376323
references.citation: J Biotechnol. 2006 Sep 1;125(2):198-209
references.pmid: 16621087
references.citation: Biotechnol Biofuels. 2013 Oct 11;6(1):147
references.pmid: 24119447
references.citation: Science. 2007 Feb 9;315(5813):804-7
references.pmid: 17289988
references.citation: Biotechnol Bioeng. 1990 Aug 20;36(5):446-52
references.pmid: 18595100
references.citation: Enzyme Microb Technol. 2011 Sep 10;49(4):353-9
references.pmid: 22112560
references.citation: Eur Biophys J. 2012 Jan;41(1):89-98
references.pmid: 22048567
references.citation: Trends Biotechnol. 2007 Apr;25(4):153-7
references.pmid: 17320227
references.citation: Microbiol Rev. 1991 Jun;55(2):303-15
references.pmid: 1886523
references.citation: J Biotechnol. 1998 Nov 18;66(1):11-26
references.pmid: 9866858