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Innovative Methods for Biomass Sugars Utilization

Li, Bin
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353092448

Abstract Details

2012, Doctor of Philosophy in Engineering, University of Toledo, Bioengineering.
The (bio)conversion of lignocellulosic biomass to biofuel (such as ethanol and furans) requires both hexose and pentose sugars released to be fully utilized to make this process cost-effective. However, the efficient xylose utilization through either fermentation or chemical conversion is the cost-limiting step. First, the major challenge for using xylose for ethanol production is that naturally occurring S. cerevisiae are unable to convert xylose, the most abundant pentose sugar in biomass hydrolysate, to ethanol. As an alternative to using genetically modified microorganisms, xylose can be exogenously isomerized to xylulose, a keto-isomer of xylose, which can be fermented by yeast. A second example is for xylose conversion to furfural. Furfural can be used as a feedstock to make gasoline, diesel or jet fuel. The chemical conversion mechanism is based on xylose dehydration. However, both the conversion of xylose and yield of furfural are currently low. Similar low conversion and yield are observed with glucose during its dehydration to hydroxymethylfurfural (HMF). However, when glucose is first isomerized to fructose, HMF yield is much improved. Thus, isomerizing xylose to xylulose may result in similar improvements to furfural yield. For both of these examples, the key for the cost-effective conversion biomass to biofuel is efficient conversion of xylose to xylulose for its more favorable downstream utilization. However, the isomerization equilibrium of xylose to xylulose using the enzyme xylose isomerase (XI) or other catalytic means predominantly favors xylose. In this dissertation, three different methods were tested to more efficiently convert xylose to xylulose; all three methods employ a sugar complexing agent (CA) to aid in shifting the xylose/xylulose equilibrium toward increased xylulose. In the first method, urease and XI were co-immobilized on a solid support to produce a high pH microenvironment within a low pH bulk fermentation media to implement simultaneous isomerization and fermentation (SIF) of ethanol by native yeast. Several water-soluble complexing agents were tested for their ability to shift the isomerization equilibrium and as well as for their impact on yeast viability and fermentation yields. In the second method, a phenylboronic acid-derivative was immobilized on a solid support to accomplish sugar complexation while immobilized XI was used for isomerization. In this system, the costs associated with the CA can be reduced due to the ease of recovery and reuse of the immobilized boronic acid. In the third method, a novel simultaneous isomerization and reactive extraction (SIRE) technique was developed to improve the isomerization of xylose to xylulose by using a two-phase system. In SIRE, the isomerization occurs in the aqueous phase and the sugar complexation occurs with a lipophilic boronic acid (CA) confined to the organic phase. This approach enables reuse of the immobilized XI and the complexing agent/organic phase, and concentration of the sugars as they are extracted and stripped from the organic phase.
Patricia Relue (Committee Chair)
Sasidhar Varanasi (Committee Co-Chair)
Ronald Fournier (Committee Member)
Guneet Kumar (Committee Member)
Sridhar Viamajala (Committee Member)
146 p.
Engineering
Biofuel; ketose sugars

Recommended Citations

Citations

  • Li, B. (2012). Innovative Methods for Biomass Sugars Utilization [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353092448

    APA Style (7th edition)

  • Li, Bin. Innovative Methods for Biomass Sugars Utilization. 2012. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353092448.

    MLA Style (8th edition)

  • Li, Bin. "Innovative Methods for Biomass Sugars Utilization." Doctoral dissertation, University of Toledo, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353092448

    Chicago Manual of Style (17th edition)

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© 2012, some rights reserved.Creative Commons License Innovative Methods for Biomass Sugars Utilization by Bin Li 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.