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.

Response of fungal community in the unpolluted and polluted (textile and distillery wastes) habitats.

37 fungal species were recorded, maximum found in textile wastewater polluted habitats (35) followed by unpolluted (15) and distillery polluted (6) habitats. Fungal diversity in sediment samples of textile wastewater polluted habitats (25) was a little lower than wastewater samples (32), whereas it varied little both in the samples of unpolluted habitats (Sambhar wetlands: 5-6; Garden tanks: 9-10) and distillery waste (3-5). Seasonal variation in species diversity was more pronounced in the textile wastewater polluted habitats. Their minimum number was often found during the rainy season while maximum in the winter season, in the polluted habitats but during summer in the unpolluted habitats. Aspergillus was the most diverse genus represented by 7 species, followed by Cladosporium and Fusarium (3 species each) while Drechslera, Rhizopus and Trichoderma had 2 species each. The remaining genera (18) were monotypic. Colony Forming Units (CFUs) were also maximum in the textile wastewater polluted habitats (5.6-1898.9 x 10(3)/L), followed by unpolluted (6.7-560.0 x 10(3)/L) and distillery waste polluted habitats (3.1-53.3 x 10(3)/L), being usually higher in the sediment samples. Their number also varied seasonally, being maximum during winter season in the water samples, whereas in summer in the sediment samples. Aspergillus fumigatus, A. niger, Cladosporium cladosporioides, C. sphaerospermum and Penicillium chrysogenum usually contributed maximum to the CFU values in the polluted as well as in unpolluted habitats.

A comparative study of Cu (II) biosorption on Ca-alginate and immobilized live and inactivated Cladosporium sp.

Spores of Cladosporium sp. were immobilized into Ca-alginate beads via entrapment. The alginate beads and both entrapped live and inactivated spores of Cladosporium sp. were used for comparison of biosorptive capacity from aqueous solutions. The factors affecting the adsorption ability on Cu (II), such as the contact time, initial pH, temperature were investigated. The results showed that the Ca-alginate beads containing live spores of Cladosporium sp. had the maximum biosorptive capacity. The biosorption equilibrium was established in about 3 h. The maximum biosorption of Cu (II) on Ca-alginate entrapping spores and no spores were obtained between pH 4.0 and 3.5. Temperature over the range of 15-45 degrees C had no significant effect on the biosorption capacity. The biosorptive capacity increased with initial concentrations in the concentration range of 30-800mg/l. The equilibrium was well described by Langmuir biosorption isotherms. The Ca-alginate beads could be regenerated using 0.1M HCl, The biosorbents were reused in three biosorption-desorption cycles with negligible decrease in biosorptive capacity.