Ethanol Tolerance in Aspergillus niger and Escherichia coli Phytase

Edward J. Mullaney, Kandan Sethumadhavan, Stephanie Boone, Abul H. J. Ullah

Commodity Utilization, Southern Regional Research Center, Agricultural Research Service, United States Department of Agriculture, New Orleans, USA.

DOI: 10.4236/aim.2012.23050                

Abstract

Despite yeast having its own native phytase, the high levels of phytate found in DDGS, a byproduct of ethanol (ETOH) fermentation, suggest that its activity is diminished in the presence of ETOH. Ethanol, a product of grain fermentation, is known to inactivate several hydrolytic enzymes but its effect on phytases is relatively unknown. In this study, two phytases, Aspergillus niger (PhyA) and Escherichia coli (AppA2), were tested for ETOH tolerance. The E. coli phytase displayed greater ethanol tolerance over fungal phytase in the 5% to 10% range. However, ETOH inactivation was found to be reversible for both the enzymes. These differences in ETOH tolerance do suggest that there is a potential to achieve higher ETOH tolerance in phytases by 'structure-function' studies to lower phytic acid levels in DDGS and for other applications.

Keywords

Phytase; Ethanol; DDGS; Fermentation; Aspergillus niger

Conflicts of Interest

The authors declare no conflicts of interest.

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