Enzymatic Hydrolysis of Rye Straw and Bermudagrass for Ethanol Production

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dc.contributor.advisor John Classen, Committee Member en_US
dc.contributor.advisor Jiayang Cheng, Committee Co-Chair en_US
dc.contributor.advisor Joel Ducoste, Committee Member en_US
dc.contributor.advisor Yuri Yamamoto, Committee Member en_US
dc.contributor.advisor Philip Westerman, Committee Chair en_US
dc.contributor.author Sun, Ye en_US
dc.date.accessioned 2010-04-02T18:52:28Z
dc.date.available 2010-04-02T18:52:28Z
dc.date.issued 2002-11-21 en_US
dc.identifier.other etd-08152002-220933 en_US
dc.identifier.uri http://www.lib.ncsu.edu/resolver/1840.16/4366
dc.description.abstract Dilute sulfuric acid pretreatment of rye straw and bermudagrass was investigated under acid concentrations of 0.6% to 1.5% (w/w) and residence time 30 min to 90 min. The pretreatment effectively solubilized the hemicellulose components to monomeric sugars such as xylose, arabinose, and galactose. Cellulose in the rye straw was not hydrolyzed into glucose during the acid pretreatment, while part of the cellulose in the bermudagrass was converted into glucose by the acid pretreatment. After enzymatic hydrolysis with excessive cellulases, the glucose yields of 30% to 52% and 46% to 81% of the theoretical potentials were obtained for rye straw and bermudagrass, respectively. The pretreated solid residues were hydrolyzed with cellulases supplemented with β-glucosidase. The addition of β-glucosidase greatly improved the glucose production rate. There was no cellobiose accumulation when the β-glucosidase loading was up to 25 CBU/g (CBU, cellobiase unit, expressed as μmol of cellobiose that is converted into glucose per minute). The conversion rate was 45% for bermudagrass hydrolyzed with cellulases of 10 FPU/g (FPU, filter paper unit, expressed as μmol of glucose produced per min with filter paper as a substrate) and &#946-glucosidase of 25 CBU/g. The further increase of enzyme loadings did not significantly improve the glucose yield. Rye straw was more resistant to enzymatic hydrolysis than bermudagrass. The conversion rate was 38% with the additions of cellulases at 15 FPU/g and &#946-glucosidase at 25 CBU/g rye straw. The production of cellulase enzymes in transgenic plants has the potential to significantly reduce enzyme costs. Expression of cellulase enzyme, Acidothermus cellulolyticus E1 endoglucanase, in transgenic duckweed Lemna minor was examined. The recombinant E1 protein was biologically active with the expression level of 0.24% of total soluble protein. HEPES (N-[2-Hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid]) buffer (pH = 8) extracted more proteins including E1 from duckweed fronds than sodium citrate buffer (pH = 4.8) and sodium acetate buffer (pH = 5). The E1 protein was thermotolerant and exhibited the optimal enzyme activity at temperature 80°C and pH 5. The E1 activity remained unchanged after heating at 60°C for 6 h. However, it was inactivated after 15-min heating at 90°C. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject transgenic duckweed and cellulases en_US
dc.subject endoglucanase E1 en_US
dc.title Enzymatic Hydrolysis of Rye Straw and Bermudagrass for Ethanol Production en_US
dc.degree.name PhD en_US
dc.degree.level dissertation en_US
dc.degree.discipline Biological and Agricultural Engineering en_US

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