title: The impact of alkali pretreatment and post-pretreatment conditioning on the surface properties of rice straw affecting cellulose accessibility to cellulases.
abstract: Rice straw was pretreated with sodium hydroxide and subsequently conditioned to reduce the pH to 5-6 by either: (1) extensive water washing or (2) acidification with hydrochloric acid then water washing. Alkali pretreatment improved the enzymatic digestibility of rice straw by increasing the cellulose accessibility to cellulases. However, acidification after pretreatment reversed the gains in cellulose accessibility to cellulases and enzymatic digestibility due to precipitation of solubilized compounds. Surface composition analyses by ToF-SIMS confirmed a reduction in surface lignin by pretreatment and water washing, and suggested that acidification precipitated a chemically modified form of lignin on the surfaces of rice straw. The spin-spin relaxation times (T2) of the samples indicated increased porosity in alkali pretreated rice straw. The acidified pretreated rice straw had reduced amounts of water in the longer T2 proton pools associated with water in the pores of the biomass likely due to back-filling by the precipitated components.
authors.affiliation: Department of Biological and Agricultural Engineering, University of California at Davis, One Shields Ave., Davis, CA 95616, USA.
authors.forename: Nardrapee
authors.initials: N
authors.lastname: Karuna
authors.affiliation: Department of Food Science and Technology, University of California at Davis, One Shields Ave., Davis, CA 95616, USA.
authors.forename: Lu
authors.initials: L
authors.lastname: Zhang
authors.affiliation: University of California at Davis Nuclear Magnetic Resonance Facility, One Shields Ave., Davis, CA 95616, USA.
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Walton
authors.affiliation: Department of Chemical Engineering & Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario M5S 3E5, Canada.
authors.forename: Marie
authors.initials: M
authors.lastname: Couturier
authors.affiliation: Department of Food Engineering, Middle East Technical University, 06800, Ankara, Turkey.
authors.forename: Mecit H
authors.initials: MH
authors.lastname: Oztop
authors.affiliation: Department of Chemical Engineering & Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario M5S 3E5, Canada.
authors.forename: Emma R
authors.initials: ER
authors.lastname: Master
authors.affiliation: Department of Biological and Agricultural Engineering, University of California at Davis, One Shields Ave., Davis, CA 95616, USA; Department of Food Science and Technology, University of California at Davis, One Shields Ave., Davis, CA 95616, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McCarthy
authors.affiliation: Department of Biological and Agricultural Engineering, University of California at Davis, One Shields Ave., Davis, CA 95616, USA. Electronic address: tjeoh@ucdavis.edu.
authors.forename: Tina
authors.initials: T
authors.lastname: Jeoh
mesh_terms: D018533:Biomass; D001709:Biotechnology / Q000379:methods*; D044602:Cellulases / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism*; D011232:Chemical Precipitation; D006851:Hydrochloric Acid / Q000494:pharmacology; D006868:Hydrolysis / Q000187:drug effects; D008031:Lignin / Q000032:analysis; D012275:Oryza / Q000187:drug effects*; D016062:Porosity; D025341:Principal Component Analysis; D066244:Proton Magnetic Resonance Spectroscopy; D012972:Sodium Hydroxide / Q000494:pharmacology*; D013499:Surface Properties; D014866:Waste Products; D014867:Water
chemical_list: D014866:Waste Products; D014867:Water; D012972:Sodium Hydroxide; D002482:Cellulose; D008031:Lignin; D044602:Cellulases; D006851:Hydrochloric Acid
keywords: Alkali pretreatment; Cellulose accessibility to cellulases; NMR; Post-pretreatment conditioning; ToF-SIMS