Animal feed production Dried Distillers Grains with

Saccharomyces cerevisiae is the dominant microorganism in the first generation of fuel ethanol production. In recent years, the worldwide bioethanol production reached around 80 billion liters per year. In a typical industrial scale bioethanol fermentation process using Saccharomyces cerevisiae, around 8-14% (v/v) ethanol is produced and the glucose to bioethanol yield is usually over 90% of the theoretical yield. In some processes, simultaneous saccharification and fermentation is applied, in which a-amylase/glucoa-mylase is mixed with Saccharomyces cerevisiae and starchy raw materials. Most of yeast cells harvested in the fermentation are recycled and sent back in order to enhance the cell concentration in the fermenter. Around 5-10% yeast cells end up in Dried Distillers Grains with Solubles (DDGS), which could be sold as animal feed. 

Dried yeasts are used extensively in animal feeds. Most distillers and brewers yeasts are incorporated by co-drying with the spent grains. Approximately 15,0001 of brewers yeast is dried for this purpose. The main use is in rations for monogastric animals. Active (ie, Hve) dry yeast is incorporated into feed for ruminants and is beUeved to aid digestion. Diets supplemented with these yeasts are also claimed to lead to increases in weight gain and productivity. Appreciable amounts of brewers yeast and torula (C. utihs) are also used in pet foods, principally for dogs and cats but also in feeds for birds, fish, mink, and bees. 

The world demand for lysine is expected to increase continually. The increasing ethanol fermentation capacity for gasohol production provides an opportunity for increased lysine production. Distillers dried grains (DDG), a by-product of ethanol fermentation used as a protein source in animal feeds, is deficient in lysine and other essential amino acids. It needs to be supplemented with lysine for full-value use. 

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