Efficient Keratinolysis of Poultry Feather Waste by the Halotolerant Keratinase from Salicola Marasensis

Sustainable development in the bio-treatment of large-scale biomass bulks requires high performance enzymes adapted to extreme conditions. An extracellular keratinolytic extract was obtained from the culture broth of a halotolerant strain of Salicola marasensis. Keratin hydrolyzing activity of the concentrated enzyme extract was observed on a 100 mg of pretreated feather waste. The concentrated enzyme was able to hydrolyze the poultry feathers by 25% after 12 h incubation. The bio-waste material was optimally hydrolyzed at pH 9 and temperature of 40 °C. Among reductants, 1,4-dithiothreitol, L-cysteine, 2-mercaptoethanol, glutathione, and sodium sulfate showed the most remarkable effect on the bio-waste keratinolysis, while the tested surfactants and urea had no significant effect on the keratinolytic activity. Hexane and hexadecane indicated strong effect on keratinase activity and bio-treatment in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) as a hydrophobic ionic liquid resulted in a maximal of 80% extraction yield of soluble proteins from feathers. Considering the stability of the extracellular keratinolytic content in [BMIM][PF₆], the observed keratinase activity was noteworthy suggesting that the secreted enzyme may contribute to the bioconversion of feather wastes.