Innovative Methods for Biomass Sugars Utilization
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University of Toledo / OhioLINK
2012
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ndltd-OhioLink-oai-etd.ohiolink.edu-toledo13530924482021-08-03T05:20:30Z Innovative Methods for Biomass Sugars Utilization Li, Bin Engineering Biofuel ketose sugars 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. 2012 English text University of Toledo / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353092448 http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353092448 unrestricted This thesis or dissertation is protected by copyright: some rights reserved. It is licensed for use under a Creative Commons license. Specific terms and permissions are available from this document's record in the OhioLINK ETD Center. |
| collection |
NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Engineering Biofuel ketose sugars |
| spellingShingle |
Engineering Biofuel ketose sugars Li, Bin Innovative Methods for Biomass Sugars Utilization |
| author |
Li, Bin |
| author_facet |
Li, Bin |
| author_sort |
Li, Bin |
| title |
Innovative Methods for Biomass Sugars Utilization |
| title_short |
Innovative Methods for Biomass Sugars Utilization |
| title_full |
Innovative Methods for Biomass Sugars Utilization |
| title_fullStr |
Innovative Methods for Biomass Sugars Utilization |
| title_full_unstemmed |
Innovative Methods for Biomass Sugars Utilization |
| title_sort |
innovative methods for biomass sugars utilization |
| publisher |
University of Toledo / OhioLINK |
| publishDate |
2012 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353092448 |
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AT libin innovativemethodsforbiomasssugarsutilization |
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