The family of keratins comprises fibrous proteins of high mechanical and chemical stability, present in skin appendages like feathers, horn, hoof or hair, as well as cytokeratins forming a part of cytoskeleton of epithelial cells. The ability of keratin degradation is a feature of many saprophytic and pathogenic microorganisms, including bacteria, fungi and streptomyces. That also occurs during caspase-mediated apoptotic processes in vertebrate cells. The mechanism of microbial keratinolysis involves action of mainly alkaline serine proteases, but additional processes like sulphitolysis or mechanical breakdown are also known. Among a wide variety of microbes, bacteria, especially from the genus Bacillus, are of interest in terms of large scale biodegradation of keratinic wastes. Diverse applications, including poultry industry or farm wastes digestion, fertilizer composts production, broiler diets supplementation and prion protein decomposition, are mentioned.