Document Type

Thesis - University Access Only

Award Date

2011

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

Abstract

Cellulosic ethanol production increases our nation's ability to produce energy from products that are otherwise deemed waste and require disposal. In addition, larger volumes of fuel can be produced, reducing the dependence on foreign oil. The objective of the study was to use mutagenesis and selection to develop strains of Candida molischiana with greater ethanol and thermal tolerance. To obtain mutagenesis, two chemical methods were executed. The first method used nitrous acid and the second chemical agent used methyl methanesulfonate MMS. The alkylating agent MMS was found to be a more potent mutagen than the deaminating nitrous acid. Surviving cells were incubated for 48 hours and then grown on a raffinose-containing minimal medium containing 2-deoxy-D- glucose. Once mutants resistant to the 2-deoxy-D-glucose were selected, the most efficient heat tolerant mutant was identified by screening at 45 degrees Celsius. The fermentation characteristics of this mutant were tested at 30, 35, 40, and 45 degrees Celsius using glucose, xylose, and a combination of both glucose and xylose as the carbon source. The fermentation characteristics of the mutant strain and the wild strain Candida molischiana ATCC 2516 were compared. Although both the mutant and the wild strain were only capable of producing ethanol using glucose as a carbon source, the results indicate that the mutant is more heat and ethanol tolerant and capable of producing higher levels of ethanol than the wild strain. The mutant isolated during this study provides new insight regarding strain improvement as it relates to heat tolerance and its potential use for large scale cellulosic ethanol production for renewable fuel sources producing ethanol using glucose as a carbon source, the results indicate that the mutant is more heat and ethanol tolerant and capable of producing higher levels of ethanol than the wild strain. The mutant isolated during this study provides new insight regarding strain improvement as it relates to heat tolerance and its potential use for large scale cellulosic ethanol production for renewable fuel sources.

Library of Congress Subject Headings

Cellulose -- Biotechnology

Biomass energy

Ethanol as fuel

Cellulosic ethanol

Renewable energy sources

Candida

Mutagenesis

Format

application/pdf

Number of Pages

102

Publisher

South Dakota State University

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