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Biochemical Saccharification of Ionic Liquid Pretreated Biomass: an Examination of Treatment Parameters and Enzyme Requirements

Barr, Christopher James
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372415335

Abstract Details

2013, Doctor of Philosophy in Engineering, University of Toledo, Chemical Engineering.
The goal of this dissertation research is to gain a deeper understanding of two major processes in the conversion of lignocellulosic biomass to monomeric sugars. These two core processes are the ionic liquid (IL) pretreatment step as well as biochemical (enzymatic) conversion of polysaccharides to monomeric sugars. Cellulose, one of the three primary components of lignocellulosic biomass, is recalcitrant to enzymatic deconstruction due, in part, to a predominantly crystalline structure. Enzymatic access to cellulose is restricted by hemicellulose and lignin. Pretreatment of lignocellulose by ionic liquids can result in a change in the cellulose structure as well as removal or redistribution of the hemicellulose and lignin. These changes result in a regenerated substrate that is more easily hydrolyzed compared to native substrates. Changes in cellulose structure as well as compositional changes within lignocellulosic biomass were examined as a response to changes in the IL incubation temperature. Maxima in 24 hour hydrolysis of glucan to glucose appears to be substrate dependent with maxima at incubation temperatures: 120ºC for poplar, 110ºC for switchgrass, and 100ºC for corn stover. At these temperatures, native cellulose I was converted to a primarily amorphous substrate where the residual crystalline cellulose exhibits predominantly cellulose II features. This optimal incubation temperature occurred before dramatic xylan losses to the IL wash. In a substrate with minimal lignin and xylan (newspaper), a maximum in enzyme digestibility was seen at a considerably lower (60ºC) pretreatment temperature. Differences in polysaccharide structure of IL pretreated poplar and switchgrass can impact hydrolysis of these polysaccharides to monomeric sugars and the formulation of the enzyme mixture needed for complete hydrolysis. These differences predicated studies with mono-component enzymes to determine critical enzyme activities and interactions. Endoglucanase, cellobiohydrolase, ß-glucosidase, endoxylanase, and ß-xylosidase were shown to be critical during hydrolysis for both poplar and switchgrass. Initial studies showed differences between poplar and switchgrass. Beneficial accessory enzymes necessary for hydrolysis of poplar were ferulic acid esterase and exopolygalacturonase while switchgrass required a-L-arabinofuranosidase and ferulic acid esterase. Further studies on switchgrass varying ß-glucosidase activity showed only a-L-arabinofuranosidase was necessary only for hydrolysis of IL pretreated switchgrass. Commercially available enzyme mixtures used for the digestion of lignocellulosic biomass contain many different types of enzymes. The composition of these enzyme mixtures are relatively unknown and are traditionally characterized by the amount of sugar released from the hydrolysis of filter paper in one hour (filter paper unit, FPU). This characterization does not quantitate the xylanolytic component within the mixture, especially accessory hemicellulases whose necessity may vary between substrates. Supplementation of the commercial mixture, Cellic CTec2, with a-L-arabinofuranosidase improved switchgrass xylose yields by 75% and resulted in complete conversion of switchgrass xylan at lower enzyme loadings than previous studies.
Constance Schall, Ph.D. (Advisor)
Maria Coleman, Ph.D. (Committee Member)
B. Leif Hanson, Ph.D. (Committee Member)
Jeffrey Mertens, Ph.D. (Committee Member)
Sasidhar Varanasi, Ph.D. (Committee Member)
234 p.
Chemical Engineering
Cellulose II; Lignocellulosic Biomass; Ionic Liquid; Cellulases; Hemicellulases; Antisolvents; EMIM-OAc

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Citations

  • Barr, C. J. (2013). Biochemical Saccharification of Ionic Liquid Pretreated Biomass: an Examination of Treatment Parameters and Enzyme Requirements [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372415335

    APA Style (7th edition)

  • Barr, Christopher. Biochemical Saccharification of Ionic Liquid Pretreated Biomass: an Examination of Treatment Parameters and Enzyme Requirements. 2013. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372415335.

    MLA Style (8th edition)

  • Barr, Christopher. "Biochemical Saccharification of Ionic Liquid Pretreated Biomass: an Examination of Treatment Parameters and Enzyme Requirements." Doctoral dissertation, University of Toledo, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372415335

    Chicago Manual of Style (17th edition)

toledo1372415335
1,071
© 2013, some rights reserved.Creative Commons License Biochemical Saccharification of Ionic Liquid Pretreated Biomass: an Examination of Treatment Parameters and Enzyme Requirements by Christopher James Barr is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Toledo and OhioLINK.