title: Improving the enzymatic hydrolysis of dilute acid pretreated wheat straw by metal ion blocking of non-productive cellulase adsorption on lignin.
abstract: Eleven salts were selected to screen the possible metal ions for blocking the non-productive adsorption of cellulase onto the lignin of dilute acid pretreated wheat straw. Mg(2+) was screened finally as the promising candidate. The optimal concentration of MgCl2 was 1 mM, but the beneficial action was also dependent on pH, hydrolysis time and cellulase loading. Significant improvement of glucan conversion (19.3%) was observed at low cellulase loading (5 FPU/g solid). Addition of isolated lignins, tannic acid and lignin model compounds to pure cellulose hydrolysis demonstrated that phenolic hydroxyl group (Ph-OH) was the main active site blocked by Mg(2+). The interaction between Mg(2+) and Ph-OH of lignin monomeric moieties followed an order of p-hydroxyphenyl (H)>guaiacyl (G)>syringyl (S). Mg(2+) blocking made the lignin surface less negatively charged, which might weaken the hydrogen bonding and electrostatically attractive interaction between lignin and cellulase enzymes.
authors.affiliation: Institute of Applied Chemistry, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Ardak
authors.initials: A
authors.lastname: Akimkulova
authors.affiliation: Institute of Applied Chemistry, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Institute of Applied Chemistry, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; Tsinghua Innovation Center in Dongguan, Dongguan 523808, China. Electronic address: zhaoxb@mail.tsinghua.edu.cn.
authors.forename: Xuebing
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Institute of Applied Chemistry, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; Tsinghua Innovation Center in Dongguan, Dongguan 523808, China.
authors.forename: Dehua
authors.initials: D
authors.lastname: Liu
mesh_terms: D000327:Adsorption; D001709:Biotechnology / Q000379:methods; D002480:Cellulase / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry; D006868:Hydrolysis; D008031:Lignin / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D008670:Metals / Q000737:chemistry; D013634:Tannins / Q000737:chemistry; D014908:Triticum / Q000737:chemistry*
chemical_list: D008670:Metals; D013634:Tannins; D002482:Cellulose; D008031:Lignin; D002480:Cellulase; D008274:Magnesium
keywords: Enzymatic hydrolysis; Lignocellulose; Metal ions; Non-productive adsorption; Phenolic hydroxyl group