Degradation of keratin substrates by keratinolytic fungi

Background: The hydrolysis of keratin wastes by microorganisms is considered a biotechnological alternative for recycling and valorization through keratinolytic microorganisms. Despite their resistant structure, keratin wastes can be efficiently degraded by various microorganisms through the secretion of keratinases, which are promising enzymes for several applications, including detergents, fertilizers, and leather and textile industry. In an attempt to isolate keratinolytic microorganisms that can reach commercial exploitation as keratinase producers, the current work assesses the dynamics of keratin biodegradation by several keratinolytic fungal strains isolated from soil. The activity of fungal strains to degrade keratin substrates was evaluated by SEM, FTRIR-ATR spectra and TGA analysis. Results: SEM observations offered relevant information on interactions between microorganism and structural elements of hair strands. FTIR spectra of the bands at 1035­1075 cm-1 assigned to sulfoxide bond appeared because of S­S bond breaking, which demonstrated the initiation of keratin biodegradation. According to TGA, in the second zone of thermal denaturation, where keratin degradation occurs, the highest weight loss of 71.10% was obtained for sample incubated with Fusarium sp. 1A. Conclusions: Among the tested strains, Fusarium sp. 1A was the most active organism in the degradation process with the strongest denaturation of polypeptide chains. Because keratinolytic microorganisms and their enzymes keratinases represent a subject of scientific and economic interest because of their capability to hydrolyze keratin, Fusarium sp. 1A was selected for further studies.

Electrophoretic variation of hair proteins

Hair follicle cells secrete a complex assortment of proteins that form the hair shaft, and can be classified into two major groups. The lowsulfur proteins are keratins that contribute to the backbone of intermediate filaments, and the high-sulfur proteins are associated with these filaments. In the present investigation we describe a comparative electrophoretic study of normal human hair proteins from 182 individuals, including some families. Hair proteins were extracted in urea buffer (pH 9.3), examined by 1O per cent polyacrylamide gel electrophoresis (pH 8.8) in the presence of sodium dodecyl sulfate and stained with Coomassie brilliant blue. Eighteen bands appeared and were reproducible in most individuals, with apparent molecular mass ranging from 10.0 to approximately 100 kDa. Based on the most prominent bands, an electrophoretic profile defined as the "frequent profile" was observed. This profile was observed in 180 individuais and consisted of 6 prominent bands, 4 of them of apparent molecular mass in the 407O-kDa range, which is characteristic of keratins (61.9 ñ 1.02, 58.5 ñ 1.21, 47.9 ñ 1.58, and 45.4 ñ 1.53 kDa), and 2 bands with lower molecular mass (18.9 ñ 0.75 and 13.7 ñ 0.91 kDa). In 2 samples from unrelated women, an additional band of 42.1 ñ 1.72 kDa appeared. The meaning of this variant is still under investigation.