Keratinous Wastes Research Articles

Keratinolytic potential of bacterial endophytes isolated from Capsicum chinense of Northeast India

Recent times highly demand an efficient and cost-effective alternative for keratin waste degradation. Studies have shown that microbial hydrolysis of keratin waste is a popular biotechnological substitute for the process of ker-atin waste valorization, which is achieved through the microbial keratinases. To sequester keratinolytic microorganisms with potential to influence com-mercial utilization as keratinase manufacturers, the present work evaluates the endophytic bacterial strains isolated from the host plant Capsicum chinense. Spectrophotometric analysis revealed that out of 4 isolated bacte-rial strains from the root and shoot parts of C. chinense, 1 strain showed sig-nificant caseinolytic and keratinolytic activities. The caseinase enzyme was measured spectrophotometrically and found to be 6.3 U/ml and the keratinase production was measured to be 93U/ml. Bacillus subtilis strain was used as a positive control. Molecular identification showed the efficient endophyte Cb4 to be Enterobacter sps, while the lesser efficient isolate Cb1 was identified as Proteus sps. The potential of the bacterial strains to dena-ture keratin substrates was assessed by SEM, FTIR spectra analysis. Bacterial endophytes isolated from the roots and shoots of C. chinense were tested for their economic importance to replace severe chemical approaches for remediating the environment. The results confirmed the amplified efficacy of the host plant, harboring the beneficial bacterial endophytes.

Chryseobacterium aquifrigidense FANN1 Produced Detergent-Stable Metallokeratinase and Amino Acids Through the Abasement of Chicken Feathers

Microbial keratinases’ versatility in the beneficiation of keratinous waste biomass into high-value products prompts their application in diverse spheres hence, advancing green technology and the bioeconomy. Consequently, a feather-degrading Chryseobacterium aquifrigidense FANN1 (NCBI: MW169027) was used to produce keratinase, and its biochemical properties were determined. The optimization of physicochemical parameters and analysis of the free amino acid constituents of the feather hydrolysate were also carried out. FANN1 showed a maximum keratinase yield of 1,664.55 ± 42.43 U/mL after 72 h, at optimal process conditions that included initial medium pH, incubation temperature, inoculum size, and chicken feather concentration of 8, 30°C, 4% (v/v), and 15 (g/L), respectively. Analysis of degradation product showed 50.32% and 23.25% as the protein value and total free amino acids, respectively, with a relatively high abundance of arginine (2.25%) and serine (2.03%). FANN1 keratinase was optimally active at pH 8.0 and relatively moderate to high temperature (40–50°C). EDTA and 1,10-phenanthroline inhibited the keratinase activity, and that suggests a metallo-keratinase. The enzyme showed remarkable stability in the presence of chemical agents, with residual activity 141 ± 10.38%, 98 ± 0.43%, 111 ± 1.73%, 124 ± 0.87%, 104 ± 3.89%, 107 ± 7.79%, and 112 ± 0.86% against DTT, H2O2, DMSO, acetonitrile, triton X-100, tween-80, and SDS, respectively. The residual activity of FANN1 keratinase was enhanced by Sunlight (129%), Ariel (116%), MAQ (151%), and Surf (143%) compared to the control after 60 min preincubation. Likewise, the enzyme was remarkably stable in the presence Fe3+ (120 ± 5.06%), Ca2+ (100 ± 10.33%), Na+ (122 ± 2.95%), Al3+ (106 ± 10.33%); while Co2+ (68 ± 8.22%) and Fe2+ (51 ± 8.43%) elicited the most repressive effect on keratinase activity. The findings suggest that C. aquifrigidense FANN1 is a potential candidate for keratinous wastes bio-recycling, and the associated keratinase has a good prospect for application in detergent formulation.

Effective bioconversion of feather-waste Keratin by Thermo-Surfactant Stable Alkaline Keratinase produced from Aspergillus sp. DHE7 with promising biotechnological application in detergent formulations

Keratin-rich wastes are troublesome pollutants that their accumulation could lead to environmental problems. Microbial degradation of keratin wastes has emerged as an alternative bio-catalyst to steam-pressure cooking and alkali hydrolysis for the recycling of such residues to value-added products. The current work investigates the purification and biochemical characterisation of an extracellular keratinase from new Aspergillus sp. DHE7 using turkey feathers as substrate. The enzyme was purified 31-fold with a final yield of 37.5%. Purified keratinase is monomeric and its molecular mass was estimated to be 33 kDa as demonstrated on SDS-PAGE. The enzyme was active in wide range of pH (7.0–11) and temperature (37–70 °C) profiles with maximum activity at pH 8.5 and 60 °C. The activity was strongly suppressed by phenylmethylsulfonyl fluoride (93.4% inhibition) and moderately inhibited by EDTA (41.2% inhibition), suggesting that the current keratinase belongs to serine-metalloprotease. Bivalent cations, such as Ca2+, Zn2+, and Mn2+, enhanced enzyme activity by 165.7%, 176.3%, and 194.8%, respectively. The purified keratinase exhibited a wide proteolytic activity towards soluble and insoluble protein substrates displaying its greater activity toward casein, keratin, bovine serum albumin, and gelatin, followed by feathers, goat hair, and wool, and was substantially stable and compliant with surfactants and commercial laundry detergents. The Km, Vmax, Kcat and Kcat/Km values on keratin were 2.2 mg/mL, 2702.7 U/mL, 136.5 s−1 and 62.04 (s−1/mg mL−1), respectively. According to these characteristics, Aspergillus sp. DHE7 keratinase is suggested as a potential candidate for use in detergent formulations (as an additive) and in various biotechnological applications.

Prospects of application of iron-containing carbon-paste electrode in electrochemical analysis

This paper carries out a study of an environmentally friendly natural material for creating a carbon-paste electrode and its application for Fe(II) determination. The electrode-active material (iron-containing carbonized keratin waste) was characterized by scanning electron microscopy (SEM), thermal analysis (DTA, TGA), and FT-IR spectroscopy. The advantages of an electrode modified with composite material are a high selectivity coefficient, a sufficiently wide range of linearity of the electrode pH function for iron (II) ions due to the presence of iron (III) oxide in the carbonation product. The analytical characteristics of the electrode containing Fe (III) were determined in the direct potentiometry mode with a relative error of about 8% and the potentiometric titration (chelatometry) mode with a change in the electrode potential of 4.4 mV and a relative error of 0.2%.

Keratinases Produced by Aspergillus stelliformis, Aspergillus sydowii, and Fusarium brachygibbosum Isolated from Human Hair: Yield and Activity.

Twenty fungal strains belonging to 17 species and isolated from male scalp hair were tested for their capacity to hydrolyze keratinous material from chicken feather. The identification of the three most efficient species was confirmed by sequencing of the internal transcribed spacer (ITS) region of rDNA. Activities of fungal keratinases produced by Aspergillus stelliformis (strain AUMC 10920), A. sydowii (AUMC 10935), and Fusarium brachygibbosum (AUMC 10937) were 113, 120, and 130 IU mg−1 enzymes, respectively. The most favorable conditions were at pH 8.0 and 50 °C. Keratinase activity was markedly inhibited by EDTA and metal ions Ca+2, Co+2, Ni+2, Cu+2, Fe+2, Mg+2, and Zn+2, with differences between the fungal species. To the best of our knowledge, this is the first study on the activity of keratinase produced by A. stelliformis, A. sydowii, and F. brachygibbosum. F. brachygibbosum keratinase was the most active, but the species is not recommended because of its known phytopathogenicty. Aspergillus sydowii has many known biotechnological solutions and here we add another application of the species, as producer of keratinases. We introduce A. stelliformis as new producer of active fungal keratinases for biotechnological solutions, such as in the management of keratinous waste in poultry industry.

Molecular strategies to increase keratinase production in heterologous expression systems for industrial applications.

Keratinase is an important enzyme that can degrade recalcitrant keratinous wastes to form beneficial recyclable keratin hydrolysates. Keratinase is not only important as an alternative to reduce environmental pollution caused by chemical treatments of keratinous wastes, but it also has industrial significance. Currently, the bioproduction of keratinase from native keratinolytic host is considered low, and this hampers large-scale usage of the enzyme. Straightforward approaches of cloning and expression of recombinant keratinases from native keratinolytic host are employed to elevate the amount of keratinase produced. However, this is still insufficient to compensate for the lack of its large-scale production to meet the industrial demands. Hence, this review aimed to highlight the various sources of keratinase and the strategies to increase its production in native keratinolytic hosts. Molecular strategies to increase the production of recombinant keratinase such as plasmid selection, promoter engineering, chromosomal integration, signal peptide and propeptide engineering, codon optimization, and glycoengineering were also described. These mentioned strategies have been utilized in heterologous expression hosts, namely, Escherichia coli, Bacillus sp., and Pichia pastoris, as they are most widely used for the heterologous propagations of keratinases to further intensify the production of recombinant keratinases adapted to better suit the large-scale demand for them. KEY POINTS: • Molecular strategies to enhance keratinase production in heterologous hosts. • Construction of a prominent keratinolytic host from a native strain. • Patent analysis of keratinase production shows rapid high interest in molecular field.

Chicken Feather Waste Hydrolysate as a Superior Biofertilizer in Agroindustry.

Billions of tons of keratinous waste in the form of feathers,antlers, bristles, claws,hair, hoofs, horns, and wool are generated by different industries and their demolition causes environmental deterioration.Chicken feathers have 92% keratin that can be a good source of peptides, amino acids, and minerals. Traditional methods of feather hydrolysis require large energy inputs, and also reduce the content of amino acids and net protein utilization values. Biological treatment of feathers with keratinolytic microbes is a feasible and environmental favorable preference for the formulation of hydrolysate that can be used asbioactive peptides, protein supplement, livestock feed, biofertilizer, etc. The presence of amino acids, soluble proteins, and peptides in hydrolysate facilitates the growth of microbes in rhizosphere that promotes the uptake and utilization of nutrients from soil. Application of hydrolysate enhances water holding capacity, C/N ratio, and mineral content of soil. The plant growth promoting activities of hydrolysate potentiates its possible use in organic farming, and improves soil ecosystem and microbiota. This paper reviews the current scenario on the methods available for management of keratinous waste, nutritional quality of hydrolysate generated using keratinolytic microbes, and its possible application as plant growth promoter in agroindustry.

Engineered pro-peptide enhances the catalytic activity of keratinase to improve the conversion ability of feather waste.

Keratinase is an attractive industrial enzyme that can specifically catalyze keratin waste to obtain value-added products. A challenge to the application of keratinase is improving catalytic capacity to achieve efficient hydrolysis. In this study, we effectively expressed the keratinase gene from Bacillus licheniformis BBE11-1 in Bacillus subtilis WB600 based on pro-peptide engineering. Partial deletion of the pro-peptide sequence and the substitution of amino acid at the pro-peptide cleavage site (P1) suggested that the "chaperone effect"and "cleavage efficiency"of the pro-peptide determine the activity of the mature enzyme. Subsequently, seven target sites that can increase the activity of the mature enzyme by 16%-66% were obtained through the multiple sequence alignment of pro-peptides and site-directed mutation. We further performed combinatorial mutations at six sites based on the design principle of three-codon saturation mutations and obtained mutant 2-D12 (236.8 KU/mg) with a mature enzyme activity of 186% of the original (127.6 KU/mg). Finally, continuous fermentation was carried out in a 5-L bioreactor for 22 h, and the activity of the 2-D12 mature enzyme was increased to 391.6 KU/mg. Most importantly, 2-D12 could degrade more than 90% of feather waste into amino acids and peptides within 12 h with the aid of sulfite.

Keratinolytic protease from Pseudomonas aeruginosa for leather skin processing

BackgroundThe leather industry generates huge volume of waste each year. Keratin is the principal constituents of this waste that is resistant to degradation. Some bacteria have the ability to degrade keratin through synthesis of a protease called keratinase that can be used as sources of animal feed and industrial production of biodiesel, biofertilizer, and bioplastic. Majority of the studies focused on keratin degradation using gram-positive bacteria. Not much of studies are currently available on production of keratinase from gram-negative bacteria and selection of best parameters for the maximum production of enzyme. The aim of this study was to isolate and characterize both groups of bacteria from soil for keratinase and optimize the production parameters. ResultsA total of 50 isolates were used for initial screening of enzyme production in skim milk, casein, and feather meal agar. Out of 50, five isolates showed significantly higher enzyme production in preliminary screening assays. Morphological and biochemical characterization revealed 60% of the isolates as gram-negative bacteria including two highest enzyme-producing isolates. The isolates were identified as Pseudomonas aeruginosa through sequencing of 16S rRNA gene. Maximum production of enzyme from P. aeruginosa YK17 was achieved with 2% chicken feather, beef extract, and ammonium nitrate as organic and inorganic nitrogen sources and glucose as a carbon source. Further analysis revealed that 3% inoculum, 40 °C growth temperature and 72-h incubation, resulted in maximum production of keratinase. ConclusionThe overall results showed significant higher production of enzyme by the P. aeruginosa YK17 that can be used for the degradation of recalcitrant keratin waste and chemical dehairing in leather industries, thereby preventing environmental pollution.

Eco-friendly and Modern Method of Poultry Waste Recycling

Throughout the world, along with the benefits that poultry farming brings to the economy of each individual country, there is a large-scale problem of such byproduct of its activity as feathers. In addition, 91% of them consist of a very valuable protein source with β-keratin. Keratin itself is very poorly decomposed and further disposed component. It makes up one of the components of feathers, the part of vertebrate skin.There is a growing preference for cost-effective and ecologically friendly poultry waste management ways. And it is the keratinase enzyme, obtained as a result of the bacteria activities, that shows great potential in this area. The selection, identification and improvement of the activities of such species of bacteria which could decompose the chicken feathers is the subject of ongoing research. About 89% provided chicken feathers were disposed (in other words, utilized) by bacteria in 2 days at temperature of 37° C. Full disposal took place after 53 hours. This study provides new results on the activities of microorganisms in the sphere of feather composting, and could also serve as an instruction for improving the work of the poultry industry in the management of keratin waste.

Cladosporium sp. Isolate as Fungal Plant Growth Promoting Agent

Cladosporium species are active in protecting plants against different biotic and abiotic stresses. Since these species produced a wide range of secondary metabolites responsible for the adaptation to new habitats, plant health and performance, they are of great interest, especially for biostimulants in agriculture. Cladosporium sp. produces protein hydrolysates (PHs), a class of biostimulants, by cultivation on medium with keratin wastes (feathers) as carbon and energy sources. The aim of this study was to select a Cladosporium isolate with potential to be used as plant growth promoting agent. The characteristics of Cladosporium isolates as plants biostimulants were evaluated through several tests, such as: antagonism versus plants pathogens, effect on plant growth of secreted volatiles produced by isolates, secretion of hydrolytic enzymes, production of 3-indole acetic acid, zinc and phosphorous solubilization, capacity to promote tomato seedlings growth (pot experiments). Cladosporium isolate T2 presented positive results to all tests. Encouraging results were obtained treating tomato seedlings with PHs from isolate Cladosporium T2 cultured on medium supplemented with 1% (w/w) chicken feathers, for which growth parameters, such as stem weight, stem height, and root weight were significantly higher by 65%, 32%, and 55%, respectively, compared to those treated with water.

Key Challenges of Microbial Degradation of Keratinous Wastes.

Feather is the main waste of poultry industries and constitutes of 90% keratin. Wastes composed of keratin are insoluble and recalcitrant to degradation using conventional decomposing methods. Microbial degradation for keratinous wastes is a promising approach for being eco-friendly and economically. However, due to insolubility of keratinous waste, it has several challenges in upstream and downstream processes such as culture medium optimization, designing of bioreactor, bioreaction/flow type, bioreactor configurations considering mass and heat transfer limitations, rheology derived problems, monitoring of microbial activity, choosing of the right scale-up parameter and purification. In this study, the challenges for keratin degradation processes were discussed with the aim of opening new opportunities for keratinous waste treatments in industrial level.

Valorization of keratin waste biomass and its potential applications

Keratin is a major structural protein with high sulphur content. It is predominantly found in chicken feathers, wool, hair, hoof, and nails. Over the years, the accumulation of keratin waste has become an uncontrollable entity throughout the world. Environmental aspects may reduce the load of waste generation by waste process engineering. Such studies focus on the safe and effective conversion of keratin-based slow degradable wastes by green methods. Different methods of waste-conversion, like chemical and thermal, have been discussed. Various keratin degradation methods have been investigated like hydrolysis under pressure by using steam, enzymatic and chemical hydrolysis. The significance of keratin with potential applications and aid in the advancement of several environmentally sound bioproducts are described, including various keratin utilisation methods with its applications. More advantageous are enzymatic and bioconversion methods which assure milder conditions and preserve nutritional properties of the produced biomass. Keratinous wastes can be used as feedstock; however, appropriate processing is required to valorise the waste. In the present scenario, the accumulation of waste is causing water pollution, environmental damage and threatening human lives is discussed. At the end of the article, various critical applications, including waste process engineering, are summarised. This review concludes with a study on the conversion of keratinous waste into consumable products to minimise pollution.

Properties and Degradation of Novel Fully Biodegradable PLA/PHB Blends Filled with Keratin.

The utilization of keratin waste in new materials formulations can prevent its environmental disposal problem. Here, novel composites based on biodegradable blends consisting of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB), and filled with hydrolyzed keratin with loading from 1 to 20 wt % were prepared and their properties were investigated. Mechanical and viscoelastic properties were characterized by tensile test, dynamic mechanical thermal analysis (DMTA) and rheology measurements. The addition of acetyltributyl citrate (ATBC) significantly affected the mechanical properties of the materials. It was found that the filled PLA/PHB/ATBC composite at the highest keratin loading exhibited similar shear moduli compared to the un-plasticized blend as a result of the much stronger interactions between the keratin and polymer matrix compared to composites with lower keratin content. The differences in dynamic moduli for PLA/PHB/ATBC blend filled with keratin depended extensively on the keratin content while loss the factor values progressively decreased with keratin loading. Softening interactions between the keratin and polymer matrix resulted in lower glass transitions temperature and reduced polymer chain mobility. The addition of keratin did not affect the extent of degradation of the PLA/PHB blend during melt blending. Fast hydrolysis at 60 °C was observed for composites with all keratin loadings. The developed keratin-based composites possess properties comparable to commonly used thermoplastics applicable for example as packaging materials.

Microbial Keratinase: Next Generation Green Catalyst and Prospective Applications.

The search for novel renewable products over synthetics hallmarked this decade and those of the recent past. Most economies that are prospecting on biodiversity for improved bio-economy favor renewable resources over synthetics for the potential opportunity they hold. However, this field is still nascent as the bulk of the available resources are non-renewable based. Microbial metabolites, emphasis on secondary metabolites, are viable alternatives; nonetheless, vast microbial resources remain under-exploited; thus, the need for a continuum in the search for new products or bio-modifying existing products for novel functions through an efficient approach. Environmental distress syndrome has been identified as a factor that influences the emergence of genetic diversity in prokaryotes. Still, the process of how the change comes about is poorly understood. The emergence of new traits may present a high prospect for the industrially viable organism. Microbial enzymes have prominence in the bio-economic space, and proteases account for about sixty percent of all enzyme market. Microbial keratinases are versatile proteases which are continuously gaining momentum in biotechnology owing to their effective bio-conversion of recalcitrant keratin-rich wastes and sustainable implementation of cleaner production. Keratinase-assisted biodegradation of keratinous materials has revitalized the prospects for the utilization of cost-effective agro-industrial wastes, as readily available substrates, for the production of high-value products including amino acids and bioactive peptides. This review presented an overview of keratin structural complexity, the potential mechanism of keratin biodegradation, and the environmental impact of keratinous wastes. Equally, it discussed microbial keratinase; vis-à-vis sources, production, and functional properties with considerable emphasis on the ecological implication of microbial producers and catalytic tendency improvement strategies. Keratinase applications and prospective high-end use, including animal hide processing, detergent formulation, cosmetics, livestock feed, and organic fertilizer production, were also articulated.

Keratinolysis of chicken feather and human hair by nondermatophytic keratinophilic fungi isolated from soil

Development in food industry increases consumption of chicken by people and it is estimated that tons of poultry feathers are produced by poultry farms. Hairs are other forms of keratinous waste which is generated in huge amounts by leather industries and parlours worldwide. Chicken feathers and hairs are waste contains high-quality protein, hard to degraded. Eleven nondermatophytic keratinophilic fungi were isolated from soil by hair baiting method and were used to deteriorate hairs and feathers. Pictographic authentication showed that the microbial incidence started with surface colonization of keratinous substrate, mechanical interference of substrate by penetrating hyphae and development of broad perforating organs. Fourier Transform Infrared Spectroscopy (FTIR) analysis of degraded and undegraded hair and the feather was made. In the sulphoxide region at 1073, the band corresponding to S-O was observed with low intensity and poorly visible in control feathers, while in degraded feather intensity of the band was high in case of Chrysosporium indicum and Chrysosporium tropicum. In Hairs, S-O band was more intense in C indicum as compared to C. tropicum while it was absent in undegraded human hair. The present work observed keratin degradation activity on human hair and chicken feather by FTIR spectra which are useful in the study of structure and mechanism of keratinolysis. Keratinous waste degradation has great potential to convert them into various byproducts such as enzymes, amino acids, biofertilizer and animal feed.

Bio-degradation of Feathers Waste by the Staphylococcus epidermidis P3A

Development of industrialization is directly proportional to the development of nations. Rising industrializations also increase the pollutions. One of them is poultry industry which discharges a huge amount of keratinous waste. The present study focused on the selection of feather degrading bacteria from Barshi region of Maharashtra. Bacterial strains were grown in whole feather broth medium. Out of 16 proteolytic bacterial isolates, 9 feather degrading isolates were selected from the Parande road side feather waste dumping area. Among these isolates, P3A was selected and classified on the basis of morphological and biochemical analysis. 16S rRNA studies confirmed that the isolated strain was Staphylococcus epidermidis. Staphylococcus epidermidis P3A shows 84% feather degradation and 72 U/ml maximum keratinase activity after 96 hrs. The isolate shows potential use in feather waste disposal methods which are safe and environment friendly.

Solid waste-derived biodegradable keratin sponges for removal of chromium: A circular approach for waste management in leather industry

Abstract Sustainable consumption and production falls under UN sustainable development goal 12, which require environmentally sound management of chemicals and all wastes; and to reduce waste generation through prevention, reduction, recycling and reuse. Leather industry produce huge solid keratinous waste and chromium contaminated wastewater. In this study, a sponge is obtained from keratinous waste that is tested to remove chromium from wastewater. Removal experiments are carried out at simulated leather industry discharge conditions. Characteristics features of sponge are; its multimodal pore structure with mesopores of 3.83 nm (BET surface area 5.52 m2/g) and 66.5% of macropores as obtained by nitrogen adsorption porosimetry and volume displacement methods, respectively. Removal of chromium was optimized by multivariate method and procedure was applied for removal of chromium from synthetic and real tanning industry wastewater that showed 91% and 87.13% removal efficiency. Langmuir adsorption capacity of 270 mg/g was obtained. Desorption study showed that at pH 10 or above, sponge can be reused, and recovery of chromium is feasible. Sorption mechanism and continuous flow removal experiments were also carried out to understand the interaction and industrial viability of method. Overall finings support ‘utilization of solid waste for treatment of liquid waste’ which would add into environmentally sustainable production in leather industry.

Biochemical characterization of a surfactant-stable keratinase purified from Proteus vulgaris EMB-14 grown on low-cost feather meal.

The bioaccumulation of keratinous wastes from poultry and dairy industries poses a danger of instability to the biosphere due to resistance to common proteolysis and as such, microbial- and enzyme-mediated biodegradation are discussed. In submerged fermentation medium, Proteus vulgaris EMB-14 utilized and efficiently degraded feather, fur and scales by secreting exogenous keratinase. The keratinase was purified 14-fold as a monomeric 49kDa by DEAE-Sephadex A-50 anion exchange and Sephadex G-100 size-exclusion chromatography. It exhibited optimum activity at pH 9.0 and 60°C and was alkaline thermostable (pH 7.0-11.0), retaining 87% of initial activity after 1h pre-incubation at 60°C. The Km and Vmax of the keratinase with keratin azure were respectively 0.283mg/mL and 0.241 U/mL/min. Activity of P. vulgaris keratinase was stimulated by Ca2+, Mg2+, Zn2+, Na+ and maintained in the presence of some denaturing agents, except β-mercaptoethanol while Cu2+ and Pb2+ showed competitive and non-competitive inhibition with Ki 6.5mM and 17.5mM, respectively. This purified P. vulgaris keratinase could be surveyed for the biotechnological transformation of bioorganic keratinous wastes into valuable products such as soluble peptides, cosmetics and biodegradable thermoplastics.

Production and characterization of a novel thermo- and detergent stable keratinase from Bacillus sp. NKSP-7 with perceptible applications in leather processing and laundry industries

Keratinase has the ability to degrade the recalcitrant keratinous wastes that cannot be degraded by conventional proteases. The present study describes a novel hyperstable keratinolytic enzyme from Bacillus sp. NKSP-7, which has excellent efficiency of keratin-feather biodegradation, washing and dehairing. The production of extracellular keratinase was improved by 3.02-fold through optimization of various parameters. Purified keratinase (25 kDa) showed optimal activity at 65 °C and pH 7.5, and displayed stability over a range of pH (5.5–9.5) and temperature (20–60 °C) for 8 h. No conspicuous effect was perceived with various chemicals and organic solvents, however, the catalytic efficiency was enhanced in the presence of Ca2+, Cd2+, Na+, Mn2+, sodium sulfite, and β-mercaptoethanol. The enzyme was completely inhibited by phenylmethanesulfonyl fluoride (PMSF), suggesting that this keratinase belongs to serine protease family. It displayed prodigious stability and compatibility to salinity and commercial detergents. Enzyme exhibited great substrate specificity but high affinity was observed with keratin-rich substrates. Crude and purified keratinase revealed perceptible potential for destaining of blood-stained fabric (10 min), and dehairing of hide (8 h) without any damage. All these auspicious features make this enzyme a promising candidate for various industrial applications, especially in keratin-waste management, detergent formulations and leather processing.