Rapid world population increasing results in a rising demand for protein for both human and animal consumption. This demand is certainly become serious with overexploitation of the sea and the use of most of the available arable land as the population rapid growth continues. We are challenged with finding of new protein sources that will not require land space or costly and tedious means of production. Microorganisms could serve an ideal solution to this problem. The single cell of a microorganism is itself a perfect protein factory. Hazardous pollution occurs from agricultural and industrial wastes, e.g. whey as a serious pollutant, has stimulated interest in converting waste materials into commercially valuable products, especially single cell protein (SCP). In competing for limited resources, microorganism evolves many strategies for selective advantages; one of these is the secretion of toxic compounds that kill or arrest the growth of other species, i.e. yeast killer toxins, which could be invested in many applied fields. The present work was designed to deal with these issues through bio-conversion of agro-industerial wastes into SCP using genetically modified killer yeast