http://academic.oup.com/milmed/article-pdf/146/1/60/24125826/milmed-146-1-60.pdf

Biochemical Tests for Identification of Medical Bacteria

Microbial keratinases have become biotechnologically important since they target the hydrolysis of highly rigid, strongly cross-linked structural polypeptide “keratin” recalcitrant to the commonly known proteolytic enzymes trypsin, pepsin and papain. These enzymes are largely produced in the presence of keratinous substrates in the form of hair, feather, wool, nail, horn etc. during their degradation. The complex mechanism of keratinolysis involves cooperative action of sulfitolytic and proteolytic systems. Keratinases are robust enzymes with a wide temperature and pH activity range and are largely serine or metallo proteases. Sequence homologies of keratinases indicate their relatedness to subtilisin family of serine proteases. They stand out among proteases since they attack the keratin residues and hence find application in developing cost-effective feather by-products for feed and fertilizers. Their application can also be extended to detergent and leather industries where they serve as specialty enzymes. Besides, they also find application in wool and silk cleaning; in the leather industry, better dehairing potential of these enzymes has led to the development of greener hair-saving dehairing technology and personal care products. Further, their prospective application in the challenging field of prion degradation would revolutionize the protease world in the near future.

Microbial keratinases and their prospective applications: an overview.

Keratinases are exciting proteolytic enzymes that display the capability to degrade the insoluble protein keratin. These enzymes are produced by diverse microorganisms belonging to the Eucarya, Bacteria, and Archea domains. Keratinases display a great diversity in their biochemical and biophysical properties. Most keratinases are optimally active at neutral to alkaline pH and 40–60°C, but examples of microbial keratinolysis at alkalophilic and thermophilic conditions have been well documented. Several keratinases have been associated to the subtilisin family of serine-type proteases by analysis of their protein sequences. Studies with specific substrates and inhibitors indicated that keratinases are often serine or metalloproteases with preference for hydrophobic and aromatic residues at the P1 position. Keratinolytic enzymes have several current and potential applications in agroindustrial, pharmaceutical, and biomedical fields. Their use in biomass conversion into biofuels may address the increasing concern on energy conservation and recycling.

Biochemical features of microbial keratinases and their production and applications.

The genus Flavobacterium

Summary
Bipolaris sorokiniana (teleomorph Cochliobolus sativus ) is the causal agent of common root rot, leaf spot disease, seedling blight, head blight, and black point of wheat and barley. The fungus is one of the most serious foliar disease constraints for both crops in warmer growing areas and causes significant yield losses. High temperature and high relative humidity favour the outbreak of the disease, in particular in South Asia's intensive ‘irrigated wheat–rice’ production systems. In this article, we review the taxonomy and worldwide distribution, as well as strategies to counteract the disease as an emerging threat to cereal production systems. We also review the current understanding of the cytological and molecular aspects of the interaction of the fungus with its cereal hosts, which makes B. sorokiniana a model organism for studying plant defence responses to hemibiotrophic pathogens. The contrasting roles of cell death and H 2O2 generation in plant defence during biotrophic and necrotrophic fungal growth phases are discussed.

Bipolaris sorokiniana, a cereal pathogen of global concern: cytological and molecular approaches towards better control‡

http://www.scielo.br/pdf/bjm/v37n3/v37n3a36.pdf

Keratinolytic bacteria isolated from feather waste

A Flavobacterium sp producing a high keratinolytic activity was isolated from a poultry industry after growth on selective feather meal agar This bacterium grew on feather meal broth, producing keratinase, and was also capable of complete degradation of raw feathers The proteolytic activity was assessed in the presence of specific protease inhibitors The crude enzyme showed mainly metalloprotease character This novel isolate would have potential biotechnological use in processes involving keratin hydrolysis

Isolation and characterization of a feather-degrading bacterium from the poultry processing industry

https://scielo.conicyt.cl/pdf/ejb/v8n1/a07.pdf

Production of an extracellular keratinase from Chryseobacterium sp. growing on raw feathers

The depilatory activity of keratinolytic bacteria was investigated. Three keratinolytic bacteria isolated from feather waste were tested for their ability to grow in mineral medium containing bovine hair as sole carbon, nitrogen and energy source. The strains kr2, kr6 and kr10 grew well on bovine hair, producing proteolytic activity as judged by assay with azokeratin as substrate. The proteolytic enzymes from all three strains showed similar pH and temperature optima. Strain kr2 showed mainly serine-type protease activity, whereas kr6 and kr10 enzymes showed metalloprotease characteristics. The culture supernatants were used as crude enzyme preparations for depilatory studies on bovine pelts. All three strains were efficacious in promoting de-hairing. Microscopic analysis revealed that the epidermis was completely removed and the absence of hair in follicles was observed. Proteases of keratinolytic bacteria were efficient in promoting depilation of bovine pelts. Enzymatic de-hairing represents a suitable alternative to the conventional tannery process, with the benefit of avoiding environmental pollution. Copyright © 2003 Society of Chemical Industry

Alessandro Riffel

Papers

Keratinolytic bacteria isolated from feather waste

Isolation and characterization of a feather-degrading bacterium from the poultry processing industry

Production of an extracellular keratinase from Chryseobacterium sp. growing on raw feathers

De‐hairing activity of extracellular proteases produced by keratinolytic bacteria

Path analysis for selection of drought tolerant sugarcane genotypes through physiological components