Submitted to: Distillers Feed Research Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2010
Publication Date: 5/12/2010
Citation: Liu, K. Contribution of Fermentation Yeast to Final Amino Acid Profile in DDGS. 14th Distillers Grains Symposium, Indianapolis, IN. May 12-13, 2010.
Technical Abstract: One major factor affecting DDGS quality and market values is amino acid (AA) composition. DDGS proteins come from corn and yeast. Yet, the effect of fermentation yeast on DDGS protein quantity and quality (AA profile) has not been well documented. Based on literature review, there are at least 4 methods that have been described to estimate yeast contribution in distillers grains products. Method 1 is by hamacytometer counting of yeast cells, which estimates 20% yeast by mass in dried solubles. Method 2 is by assumption and calculation, which gives 3.9 % by mass and 5.3% by protein in DDGS. Method 3 is by the average ratio in essential AA contents of yeast/DDGS, which indicates that yeast could provide up to 50% protein in DDGS. Method 4 is by a multiple linear regression of amino acid composition (% relative) of corn and yeast, based on a recently published ARS study by the author and his colleague (Han and Liu, 2010, J. Agric. Food Chem. 58:3430-3437). It shows that fermentation yeast accounts for 20% of the DDGS AA profile, while corn accounts for the remaining 80%. The author believes that Method 4 is by far the most accurate estimation for the effect of yeast on the AA profile of DDGS and other downstream products. Since yeast has a better AA profile than corn (e.g. lysine content), investigation into yeast effect (contribution) will have a positive impact on feed and ethanol industries and at the same time increase our basic understanding of the system.