Ethanol, when mixed with gasoline, is an economical and environmentally friendly liquid
fuel. Yeast cells under anaerobic conditions can ferment glucose to ethanol. However, glucose
is expensive for industrial applications and starch is an economical alternative.
Simultaneous cold starch hydrolysis and fermentation was investigated for ethanol
production from wheat starch particles. With a view to minimize process costs while
maintaining a satisfactory ethanol yield, both a recombinant yeast cell and an inexpensive
medium were tested for their fermentation abilities. Initially, NRRL Y132 strain was compared to Muntons yeast for their abilities to produce ethanol from glucose. Both the wild-type and the recombinant NRRL Y132 strains were cultured on soluble starch to determine if the plasmid bearing strain could produce ethanol without the addition of -amylase. Finally, Muntons yeast was cultured on starch particles using both expensive and inexpensive media. Sequential hydrolysis and fermentation runs were performed using the inexpensive medium, with hydrolysis carried out at 30°C, 37.5°C, 45°C and 52.5°C.
The wild-type, NRRL Y132 strain grew faster and produced more ethanol than Muntons
yeast when cultured on glucose. Compared to the wild-type strain, the recombinant NRRL Y132
strain did not show enhanced ethanol production from soluble starch. The results of the
simultaneous hydrolysis and fermentation runs showed that the ethanol yields for runs performed
in expensive medium (0.41, 0.38 and 0.42 g ethanol / g glucose) were slightly lower than those
for runs performed in the inexpensive medium (0.46, 0.44 and 0.43 g ethanol / g glucose). The
growth rates for the expensive and inexpensive media runs were comparable. Hence, it was
concluded that the inexpensive medium can be used for ethanol production from starch particles
with good ethanol productivities. For the sequential hydrolysis and fermentation runs, it was observed that the growth rates (0.11, 0.10, 0.10 and 0.11 h-1) as well as the ethanol yields (0.44, 0.37, 0.44 and 0.39 g ethanol / g glucose) were similar in spite of the four different hydrolysis temperatures. Therefore, it was concluded that increasing the temperature above 30°C for enhancing starch particle hydrolysis does not increase fermentation productivity significantly.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-08282008-160908 |
| Date | 04 September 2008 |
| Creators | Bawa, Nancy |
| Contributors | Lin, Y., Niu, Catherine, Wang, H., Baik, O., Hill, Gordon, Roesler, W. |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-08282008-160908/ |
| Rights | unrestricted, 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 University of Saskatchewan 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. |
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