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.
Highlights
Phytate is the principal storage compound for phosphorus in plants
Despite yeast having its own native phytase, the high levels of phytate found in dried distillers grains with solubles (DDGS), a byproduct of ethanol (ETOH) fermentation, suggest that its activity is diminished in the presence of ETOH
While no information exist on ethanol tolerance in phytases, any 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 designing of phytases that retains more activity during fermentation and lower the phytic acid content of DDGS
Summary
With the increased utilization of high phytate containing plant meals over the last several decades, extensive research has focused on the deployment of phytases as an animal feed additive. This is to allow monogastric animals (swine, poultry, etc.) which lack a digestive phytase to obtain the phytate’s ortho-phosphate groups, which otherwise will be unavailable. Demands for additional bio-based fuels have spurred enhanced fermentation of corn and other grains such as sweet sorghum to produce ethanol in response to the growing demand. This has resulted in increased amounts of dried distillers grains with solubles (DDGS) emanating from this process. The achievement of a molecular modification to enhance ethanol tolerance in phytase may have further applications in enhancing the ethanol tolerance of other hydrolytic enzymes
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