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Abstract Detail

MSA - Cell and molecular biology/Physiology & Genetics

Mullaney, E. [1], Sethumadhavan, K. [1], Boone, S. [1], Ullah, A. [1].

Ethanol tolerance in Aspergillus niger and Escherichia coli phytase.

Today, a major co-product of ethanol production from yeast fermentation of grains is distillers dried grains with soluble (DDGS). The high nutritive value of DDGS has spurred attempts to expand its utilization as an animal feed. However, one problem limiting the increased utilization of DDGS for this application is that most of its phosphorus (P) is bound up in a single compound, phytate. Phytate is common in grains, but non-ruminant animals cannot digest it; therefore, supplementing DDGS with phytase is necessary when DDGS is fed to these animals. The yeast, Saccharomyces cerevisiae, generally utilized in fermentation is known to have its own phytase, but the high levels of phytate found in DDGS suggest that ethanol produced during fermentation inactivates the yeast’s native phytase. While no information exist on the ethanol tolerance of any phytase, ethanol inhibition of other hydrolytic enzymes has been reported. In this study, the ethanol tolerances of two microbial phytases that are marketed as animal feed additives are determined. While both are histidine acid phosphatases and share the same active site geometry and catalytic mechanism, one is from Aspergillus niger and the other is produced by Escherichia coli. They are also known to have their own unique catalytic characteristics. Differences in ethanol tolerance in the two enzymes can enhance our understanding of how ethanol interacts with this class of enzymes and this may contribute to the design of phytases that retain more activity during fermentation and thus lower the phytic acid content of DDGS. The achievement of a molecular modification to enhance ethanol tolerance in phytase may also have further application in other hydrolytic enzymes.

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1 - Srrc-Ars-Usda, New Orleans, LA, 70124

Phytic acid
A. niger
E. coli

Presentation Type: Poster:Posters for Topics
Session: P2
Location: Event Tent/Cliff Lodge
Date: Tuesday, July 28th, 2009
Time: 5:30 PM
Number: P2CG006
Abstract ID:199

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