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Treating Thin Stillage and Condensed Distillers Solubles with Phytase for Production of Low-Phytate Coproducts

¹Grain Chemistry and Utilization Laboratory, National Small Grains and Potato Germplasm Research Unit, U.S. Department of Agriculture, Agricultural Research Service, 1691 S 2700 W, Aberdeen, ID, 83210, U.S.A. Phone: (208) 397-4162, ext. 232. Fax: (208) 397-4165. E-mail: keshun.liu@ars.usda.gov. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity employer.

Fuel ethanol production from grains is mainly based on dry-grind processing, during which phytate is concentrated about threefold in distillers dried grains with solubles (DDGS), a major coproduct. To reduce phytate in DDGS, Natuphos and Ronozyme industrial phytase preparations were used to treat commercially made thin stillage (TS). Changes in phosphorous (P) profile were monitored, and effects of reaction temperature, time, and enzyme concentration were investigated. Results showed that at a temperature ≤60°C for Natuphos phytase (≤70°C for Ronozyme phytase) and a concentration ≤4.8 FTU/mL of TS for Natuphos phytase (≤48 FYT/mL for Ronozyme phytase), a complete phytate hydrolysis (phytate P decreased to 0) could be achieved within 5–60 min of enzymatic treatment. Reduction in phytate P was generally accompanied by increase in inorganic P, whereas total P remained relatively unchanged. When condensed distillers solubles (CDS), the concentrated form of TS, was used as the substrate, phytate hydrolysis by each of the two enzyme preparations was as effective as on TS. Because a previous study from the author's laboratory showed that all types of P are mostly concentrated in TS and CDS but much less in distillers wet grains, phytase treatments of TS and CDS described in the present study can be an effective means in producing low-phytate DDGS.