Author
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Skory, Christopher - Chris |
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Freer, Shelby |
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Bothast, Rodney |
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Submitted to: Journal of Industrial Microbiology
Publication Type: Abstract Only Publication Acceptance Date: 8/11/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Several filamentous fungi have the unique ability to hydrolyze and convert agricultural waste products directly to ethanol and/or acetate. This is possible because of the presence of extracellular hydrolytic enzymes (e.g., exoglucanases, endoglucanases, beta-glucosidases, and xylanases) that saccharify polysaccharides and the ability of these fungi to convert both pentose and hexose sugars to ethanol in high yields. This conversion is believed to occur by way of the Embden-Meyerhof-Parnas pathway to pyruvate. Pyruvate is then converted to acetaldehyde and finally to ethanol using pyruvate decarboxylase and alcohol dehydrogenase, respectively. This type of simultaneous saccharification and fermentation by a single organism offers many advantages over current technologies using multiple organisms or supplementation with costly enzymes. However, use of filamentous fungi for direct conversion of cellulose/xylose to ethanol has been limited by slow rates of conversion to ethanol. We have investigated rate limiting steps to determine ways of improving productivity. Efforts are currently directed at increasing beta-glucosidase activity to maximize the efficiency of cellulose saccharification and improving the organisms ability to convert pyruvate to ethanol. Both Aspergillus and Fusarium are being used for expression of recombinant pyruvate decarboxylase and alcohol dehydrogenase genes. It is believed that increased activity of these enzymes will lead to higher productivity rates of ethanol. |
