Bacterial Keratinases: Useful Enzymes for Bioprocessing Agroindustrial Wastes and Beyond

Abstract

Keratin-rich wastes in the form of feathers, hair, nails, and horn are highly available as byproducts of agroindustrial processing. The increased needs for energy conserving and recycling, summed with the huge increase in poultry industry, have strongly stimulated the search for alternatives for the management of recalcitrant keratinous wastes. Keratinases, which are produced by several bacteria that have been often isolated from soils and poultry wastes, show potential use in biotechnological processes involving keratin hydrolysis. Although these isolates are mostly restricted to the genera Streptomyces and Bacillus, the diversity of keratinolytic bacteria is significantly greater. Bacterial keratinases are mostly serine proteases, although increased information about keratinolytic metalloproteases, particularly from Gram-negative bacteria, became available. These enzymes are useful in processes related with the bioconversion of keratin waste into feed and fertilizers. Other promising applications have been associated with keratinolytic enzymes, including enzymatic dehairing for leather and cosmetic industry, detergent uses, and development of biopolymers from keratin fibers. The use of keratinases to enhance drug delivery in some tissues and hydrolysis of prion proteins arise as novel outstanding applications for these enzymes.

Rapid Conversion of Chicken Feather to Feather Meal Using Dimeric Keratinase from Bacillus licheniformis ER-15

“…Although, alkaline pH and high temperature would facilitate rapid feather degradation by reducing disulfide bonds [2] but is not often recommended for the direct use of feather meal in feed due to loss of some essential amino acids [3,13]. Therefore, feather degradation was studied at pH 8 and 50°C where present keratinase exhibited >60% activity [10].…”

Isolation and Molecular Identification of Keratinase-Producing Bacteria from the Sludge of Qeshm Island

“…Bacterial growth was assessed after transferring 1ml of sample-FMB mixture was to FMA (solid feather culture medium with 2% agar). In order to obtain colonies, the bacteria were first cultured on nutrient agar by streaking and then incubated at 37 ℃ for 24h (9,10). After characterization with Gram staining and morphology, the colonies were transferred and incubated in skim milk agar to separate hemolytic bacteria (11).…”

Characteristics of Feather Protein Concentrates Hydrolyzed Using Bacillus subtilis FNCC 0059

“…The application of hydro-thermal processes can lead to the loss of amino acids with low digestibility. Thus the hydrolysis process using enzymes from microbes has enormous benefits (Brandelli, 2008;Mabrouk, 2008).…”