Abstract: Stillage sludge, a by-product of sugar industry, was subjected to proximate analysis. Its protein quantity and quality was improved through fermentation with Brevibacterium flavum. A protein isolate was prepared from it. Its proximate analysis was carried out to know its nutritional potential. The amino acid profile shows that it is limiting in threoninc. The chemical score of protein isolate thus found to be 36.42. The quality of its protein was evaluated in terms of protein efficiency ratio (3.92), net protein utilization (71.27), digestibility (96.97) and biological value (73.00) by conducting a feeding trial on weanling albino rats.