Keratinolytic Potential of the Micromycete Aspergillus clavatus VKPM F-1593 and Comparison of Its Enzymes with the Commercial Keratinase Preparation

Keratin-containing wastes (feathers and bristles) make up the majority of all animal wastes, a fast-growing agricultural sector that annually increases production volume. The development of methods for environmentally friendly processing of such waste to obtain valuable resources (amino acids and oligopeptides) is an important task in modern science, including biotechnology. A way to dispose of livestock waste according to the current trends of the development of green economy is the use of microorganisms and their enzymes. The possibility of production of keratinolytic enzymes of Aspergillus clavatus VKPM F-1593 has been studied under submerged conditions with different sources of nitrogen and carbon, including the growth of the producer on animal waste. The highest target activity (96.1 E) was achieved using mixed sources of carbon and nitrogen: an inorganic source (sodium nitrate), an easily digestible organic source (fish meal hydrolysate) and a hard-to-get organic source (ground chicken feather). The variation in the content of different substrates in the fermentation media has made it possible not only to regulate the level of proteolytic activity, but also to reach the peak of producer activity on different days of cultivation. The specific activity of the keratinase of A. clavatus VKPM F-1593 (pI 9.3) with respect to different protein substrates has been compared with the activity of the commercial proteinase K preparation. Both enzymes have shown a similar level of activity with respect to most of the used substrates. However, the protease of A. clavatus VKPM F-1593 has had a greater total proteolytic activity, which confirms the prospective use of this culture for the biodegradation of animal waste.