Abstract
Paecilomyces lilacinus (Thom) Samson LPS 876, a locally isolated fungal strain, was grown on minimal mineral medium containing “hair waste,” a residue from the hair-saving unhairing process, and produced a protease with keratinolytic activity. This enzyme was biochemically characterized. The optimum reaction conditions, determined with a response surface methodology, were 60°C and pH 6.0. It was remarkably stable in a wide range of pHs and temperatures. Addition of Ca2+, Mg2+, or sorbitol was found to be effective in increasing thermal stability of the protease. PMSF and Hg2+ inhibited the proteolytic activity indicating the presence of a thiol-dependent serine protease. It showed high stability toward surfactants, bleaching agents, and solvents. It was also compatible with commercial detergents (7 mg/mL) such as Ariel, Skip, Drive, and Ace, retaining more than 70% of its proteolytic activity in all detergents after 1 h of incubation at 40°C. Wash performance analysis revealed that this protease could effectively remove blood stains. From these properties, this enzyme may be considered as a potential candidate for future use in biotechnological processes, as well as in the formulation of laundry detergents.
Highlights
Microbial proteases are the most widely exploited industrial enzymes with major application in detergent formulations [1, 2]
Keratinases constitute a group of enzymes capable of disrupting the highly stable keratin structure consisting of disulfide, hydrogen, and hydrophobic bonds in the form of α-helices and β-sheets [5]
We report the biochemical characterization, including the effect of some surfactants and bleaching agents on enzyme stability, its compatibility with various commercial liquid and solid detergents and a study of an efficient stabilization method toward heat inactivation, of the keratinase produced by Paecilomyces lilacinus growing on hair waste substrate
Summary
Microbial proteases are the most widely exploited industrial enzymes with major application in detergent formulations [1, 2]. “Subtilisin Carlsberg” has been protein engineered to obtain a bleachstable, alkaline protease by molecular modification [4], but still, there is always a need for newer thermostable alkaline proteases which can withstand bleaching agents present in detergent. Among these different proteases, keratinases constitute a group of enzymes capable of disrupting the highly stable keratin structure consisting of disulfide, hydrogen, and hydrophobic bonds in the form of α-helices and β-sheets [5]
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