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Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/5/2013 Publication Date: 1/7/2014 Citation: Liu, K. 2014. Treating thin stillage or condensed distillers solubles with phytase for production of low phytate co-products. Cereal Chemistry. 91:72-78. Interpretive Summary: In recent years, distillers dried grains with solubles (DDGS), a co-product of a major process (dry grind) for making fuel ethanol from grains, has emerged as a major feed commodity in the global market, as more U.S. grown corn is used in the fuel ethanol industry. One major concern with DDGS relates to the amount and the form of phosphorus (P) present; both affect the retention of P in ingested feeds by animals (bioavailability) and the amount of P excreted in wastes. During dry grind processing, phytate was concentrated about three fold and this limits DDGS uses as feed for non-ruminants. In an early study conducted at the author’s lab, it was observed that all types of P, including phytate P, inorganic P, total P and the rest of P, were concentrated in thin stillage (TS) and its condensed form (condensed distillers solubles or CDS). Since distillers wet grains (DWG) was found to have a similar P profile as the feedstock corn, the increase in P concentrations (including phytate P) in DDGS was totally due to addition of CDS. Therefore, it is hypnotized that TS or CDS would be the ideal substrate for phytase addition in order to effectively produce low phytate DDGS. To prove the hypothesis, the present study was conducted by treating TS or CDS with two commercial phytase preparations. Technical Abstract: Fuel ethanol production from grains is mainly based on dry grind processing, during which phytate is concentrated about three fold in distillers dried grains with solubles (DDGS), a major co-product. For reducing phyate in DDGS, two industrial phytase preparations (Natuphos and Ronozyme) 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 show that at a temperature = 60°C (=70°C for Ronozyme) and a concentration = 4.8 FTU/ml TS (= 48 FYT/ml for Ronozyme), a complete phytate hydrolysis (phytate P decreased to 0) could be achieved within 5-60 min of enzymatic treatments. Reduction in phytate P was generally accompanied by increase in inorganic P, while total P remained relatively unchanged. When condensed distiller solubles (CDS), the concentrated form of TS, was used as substrate, phytate hydrolysis by the enzymes was as effective as with TS. Because a previous study showed that all types of P are concentrated in TS and CDS but not in distillers wet grains, phytase treatments of TS or CDS described in this study can be an effective means in producing low phytate DDGS. |
