The present invention provides compositions and methods designed to increase value output of a fermentation reaction that yields a first product, intended for commercialization, such as ethanol, and a fermentation residual used, for example, as animal feed. The methods involve using microorganisms in the fermentation process that have been modified so as to yield a residual having greater value that a residual produced in the process by a microorganism not so modified. In particular, the present invention contemplates using microorganisms in a fermentation process that have been modified to increase production of a nutrient, such as an essential amino acid, thereby reducing the need to supplement the nutrient in the animal's diet. The present invention also provides a modified fermentation residual of higher commercial value. Also provided in the present invention are complete animal feeds, nutritional supplements comprising the subject ferment residuals. Further provided by the present invention is a method of performing fermentation, a modified fermentative microorganism and a genetic vehicle for modifying such microorganism.