Purification of keratinase from poultry farm isolate-Scopulariopsis brevicaulis and statistical optimization of enzyme activity

Production and concentration of keratinases and application of fermentation residual in removing hexavalent chromium

The production of keratinases was evaluated in submerged fermentation with Aspergillus niger and by pigs' swine hair in a batch bioreactor. Experimental planning was performed to assess the interaction between different variables. The enzyme extract produced was characterized at various pH and temperatures and subjected to enzyme concentration using a biphasic aqueous system and salt/solvent precipitation techniques. In addition, the substrate's potential in reducing hexavalent chromium from synthetic potassium dichromate effluent with an initial concentration of 20 mg L-1 of chromium was evaluated. The resulting enzyme extract showed 89 ± 2 U mL-1 of keratinase. The enzyme concentration resulted in a purification factor of 1.3, while sodium chloride/acetone and ammonium sulfate/acetone resulted in a purification factor of 1.9 and 1.4, respectively. Still using the residual substrate of swine hair from the fermentation, a 94% reduction of hexavalent chromium concentration occurred after 9 h of reaction. Thus, the study proved relevant for producing keratinases, with further environmental applicability and the possibility of concentrating the extract via low-cost processes.

Isolation, identification, and molecular characterization of potential keratinolytic fungus sp. from Southern Assam: relevance to poultry wastes and its biological management

Feather waste is a highly prevalent form of keratinous waste that is generated by the poultry industry. The global daily production of feather waste has been shown to approach 5 million tons, typically being disposed of through methods such as dumping, landfilling, or incineration which contribute significantly to environmental pollutions. The proper management of these keratinous wastes is crucial to avoid environmental contamination. The study was carried out to isolate the keratinolytic fungi from the poultry disposal sites of different region of North-East India to evaluate its potential in bioremediation of the feathers wastes. Out of 12 fungal strains isolated from the sites, the fungus showing the highest zone of hydrolysis on both the skim milk and keratin agar medium was selected for the study and the molecular identification of the isolate was performed through DNA sequence analysis by amplifying the internal transcribed spacer (ITS) region. The sequence results showed higher similarity (above 95%) with Aspergillus spp. and was named Aspergillus sp. Iro-1. The strain was further analyzed for its feather degrading potential which was performed in submerged conditions under optimized conditions. The study showed that the strain could effectively degrade the feathers validated through weight loss method, and the structural deformations in the feathers were visualized through scanning electron microscopy (SEM). Aspergillus sp. Iro-1 was obtained from the southern region of Assam. It would be of great importance as the implementation of this sp. can help in the bioremediation of feathers wastes in this region. This is the first study of identification of feather degrading fungus from southern part of Assam (Barak).

Isolation, Identification and Characterization of Keratin-Degrading Streptomyces rochei AM8

Keratinolytic microorganisms are highly valuable for decomposition of poultry waste. This study aimed to isolate keratin-decomposing actinobacteria from poultry farm soils and examine their capacity to decompose feathers. Soil samples were placed in a basal medium with feather meal, which is a deposit of carbon and nitrogen. Nine actinobacterial strains were isolated. Actinobacteria were cultured in the media to show clear feather-decomposing potential. Actinobacterial strains were identified using 16S ribosomal RNA (rRNA) sequencing as being related to Streptomyces rochei AM8. Thus, the supernatant of S. rochei AM8 exhibited keratinolytic enzyme activity. Increased biodecomposition of feathers was recorded in a keratinase assay (0.782 U/mL) for separated cultures. The ability of the selected microorganisms to decompose feathers may be an effective biotechnological solution for managing feather waste from poultry.

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.

Protease from Mucor subtilissimus UCP 1262: Evaluation of several specific protease activities and purification of a fibrinolytic enzyme

The industrial demand for proteolytic enzymes is stimulating the search for new enzyme sources. Fungal enzymes are preferred over bacterial enzymes, and more effective and easier to extract. The aim of this work was to evaluate the potential of protease production by solid state fermentation (SSF) of Mucor subtilissimus UCP 1262, evaluate different specific activities, purify and partially characterize the enzyme in terms of biochemical as to the optimal pH and temperature. Initially, the enzyme crude extract was screened for 3 different proteolytic activities, collagenolytic (161.4 U/mL), keratinolytic (39.6 U/mL) and fibrinolytic (26.1 U/mL) in addition to conventional proteinase activity. After ammonium sulfate precipitation, the active fractions with fibrinolytic activity were dialyzed in 15 mM Tris-HCl buffer, pH 8, loaded onto DEAE-Sephadex A50 ion-exchange column and gel filtrated through Superdex 75 HR10/300. The enzyme showed a fibrinolytic maximum activity at 40 C and pH 9,0. The purified enzyme showed activity against a chromogenic chymotrypsin substrate, SDS-PAGE showing a molecular mass of approximately 70 kDa and, the specific activity of 25.93 U/mg. These characteristics suggest that the enzyme could be and efficiently produced in a simple and low-cost way using Mucor subtilissimus UCP 1262 in SSF.

Reactional ultrasonic systems and microwave irradiation for pretreatment of agro-industrial waste to increase enzymatic activity

Pretreatment of keratinous residues using an ultrasonic reaction system provides greater enzymatic production in less time. This is a promising technology for measuring enzyme activity and microwave processes. In the present work, an ultrasonic probe reaction system was used to evaluate the potential of swine hair pretreatment. The pretreated material was submerged with non-pretreated residues for 9 days to obtain the enzyme. Enzyme activity was measured in the extracts obtained using the ultrasonic probe, ultrasonic bath, and microwave. We also used the enzymatic concentration technique with NaCl and acetone. Homemade enzymatic extracts were evaluated for their ability to degrade swine hair and chicken feathers by comparing them with the activities commercial enzymes. Macrobeads gave greater energy dissipation in less time, providing greater enzyme activity (50.8 U/mL over 3 days). In terms of waste degradation, non-pretreated swine hair was more promising. The ultrasonic probe reaction system had the potential to evaluate increased enzyme activity (38.4% relative activity) and the enzyme concentration increased activity by 53.5%. The homemade enzymatic extract showed promise for degradation of keratinous residues.

Biochemical characterization of an alkaline surfactant-stable keratinase from a new keratinase producer, Bacillus zhangzhouensis

A new keratinase producer, Bacillus sp. BK111, isolated from a poultry feather was identified as Bacillus zhangzhouensis, which is the first report for its keratinolytic activity. The keratinase production was optimized, followed by the enzyme purification and characterization using biochemical assays. A 2.34-fold increase was observed in the enzyme production under optimized conditions. The enzyme was characterized as a serine protease with 42 kDa molecular weight, stable in a wide range of temperature and pH with maximum keratinolytic activity at 60 °C and pH 9.5. The enzyme had a wide range of different substrates with the best performance on the feather meal substrate. Metal ions of Ca²⁺, K⁺, Na⁺ and Mn²⁺ enhanced the enzyme activity. The enzyme showed a great deal of stability in the presence of ethanol, methanol, acetone, 2-propanol, dimethyl sulfoxide, Tween-80 and Triton X-100. Dithiothreitol (DTT), as a reducing agent, caused a twofold increase in keratinolytic activity. The half-life of the enzyme at optimum temperature was calculated to be 125 min and the ratio of keratinolytic:caseinolytic for the enzyme was 0.8. Our results showed the remarkable features of the enzyme that make it suitable for biotechnological usages.

Mycorrhiza: a natural resource assists plant growth under varied soil conditions

In this overview, the authors have discussed the potential advantages of the association between mycorrhizae and plants, their mutual accelerated growth under favorable conditions and their role in nutrient supply. In addition, methods for isolating mycorrhizae are described and spore morphologies and their adaptation to various conditions are outlined. Further, the significant participation of controlled greenhouses and other supported physiological environments in propagating mycorrhizae is detailed. The reviewed information supports the lack of host- and niche-specificity by arbuscular mycorrhizae, indicating that these fungi are suitable for use in a wide range of ecological conditions and with propagules for direct reintroduction. Regarding their prospective uses, the extensive growth of endomycorrhizal fungi suggests it is suited for poor-quality and low-fertility soils.

Comprehensive insights into microbial keratinases and their implication in various biotechnological and industrial sectors: A review

Enormous masses of keratinous wastes are annually accumulated in the environment as byproducts of poultry processing and agricultural wastes. Keratin is a recalcitrant fibrous protein, which represents the major constituent of various keratin-rich wastes, which released into the environment in the form of feathers, hair, wool, bristle, and hooves. Chemical treatment methods of these wastes resulted in developing many hazardous gases and toxins to the public health, in addition to the destruction of several amino acids. Accordingly, microbial keratinases have been drawing much interest as an eco-friendly approach to convert keratinous wastes into valuable products. Numerous keratinolytic microorganisms have been identified, which revealed the competence to hydrolyze keratins into peptides and amino acids. Several types of keratinolytic proteases have been produced that possess diverse biochemical characteristics, conferring them the versatility for implementing in multifarious applications such as detergents, leather and textile industries, animal feeding, and production of bio-fertilizers, in addition to medical and pharmaceutical treatments. This review article emphasizes the significance of keratinases and keratinase based-products via comprehensive insights into the keratin structure, diversity of keratinolytic microorganisms, and mechanisms of keratin hydrolysis. Furthermore, we discuss the biochemical properties of the produced keratinases and their feasible applications in diverse disciplines.

Recombinant expression and biochemical characterization of a novel keratinase BsKER71 from feather degrading bacterium Bacillus subtilis S1-4

Bacillus subtilis S1-4, isolated from chicken feather could efficiently degrade feathers by secreting several extracellular proteases. In order to get insight into the individual protease involved in keratin hydrolysis, a keratinase designed as BsKER71 was cloned and expressed in Bacillus subtilis WB600. In silico analysis revealed that BsKER71 protein contained a mature protein of 36.1 kDa. Further, purified BsKER71 could hydrolyze a variety of natural proteins, such as fibrous protein, collagen protein, casein, keratin and bovine serum albumin. In addition, this keratinase exhibited high enzyme activity in a wide range of pH and optimal pH of 10.0 and 9.0 in the hydrolysis of casein and keratin, respectively. Similarly, the optimal temperature was 55 °C and 50 °C for the hydrolysis of above two substrates, respectively. The hydrolytic activity was significantly inhibited by phenylmethanesulfonyl fluoride (PMSF), indicating the presence of serine residue in the active site. Moreover, ethylenediaminetetraacetic acid (EDTA) and phenanthroline moderately inhibited the hydrolytic activity. The catalytic activity was stimulated by Mg²⁺ and Ca²⁺, but greatly inhibited by Cu²⁺. Furthermore, several chemicals exhibited different effects on the hydrolysis of casein and keratin by BsKER71. These results provided a better understanding of BsKER71 from feather degrading bacterium B. subtilis S1-4.

Biotechnological Processes in Microbial Amylase Production

Amylase is an important and indispensable enzyme that plays a pivotal role in the field of biotechnology. It is produced mainly from microbial sources and is used in many industries. Industrial sectors with top-down and bottom-up approaches are currently focusing on improving microbial amylase production levels by implementing bioengineering technologies. The further support of energy consumption studies, such as those on thermodynamics, pinch technology, and environment-friendly technologies, has hastened the large-scale production of the enzyme. Herein, the importance of microbial (bacteria and fungi) amylase is discussed along with its production methods from the laboratory to industrial scales.

Biodegradation of feather waste keratin by a keratinolytic soil fungus of the genus Chrysosporium and statistical optimization of feather mass loss

This paper assesses the ability of strains of Aphanoascus fulvescens and Chrysosporium articulatum isolated from soil (phaesol) to degrade native feather keratin. Strains were identified based on phenotypic traits and nucleotide sequencing. Response Surface Methodology was used to optimize cultivation conditions exhibiting the highest keratinolytic activity. The experiments were based on Box-Behnken designs for the loss of substrate mass (chicken feathers). While substrate mass loss is an “economic coefficient” that reliably indicates feather keratin degradation, it has not been studied before. Stationary liquid cultures of five selected strains were conducted in laboratory conditions at 28 °C using poultry feathers (1 g) as the sole source of carbon, nitrogen and energy. Enzymatic activities, keratin mineralization products and substrate mass loss were determined periodically. The mineralization of keratin proteins by strains yielded a high number of ammonium ions alkalinizing the medium. Increased ammonium ions inhibited the activity of caseinian protease and keratinase. A decrease in the concentration of these ions induced proteolytic enzymes, chiefly the activity of keratinase, at the end of fungal cultivation. Keratinase activity was related to protein- and peptide release and that of caseinian protease to sulfate ions. The highest loss of substrate mass in comparison to the reference strain CBS104.62 (35.4%) was recorded for Aphanoascus fulvescens B21/4-5 (65.9%). Based on a Box-Behnken design, the maximum loss of substrate mass for the Aphanoascus fulvescens strain (71.08%) can be achieved at pH 7.58 and temperature 28.7 °C.

Microbial decomposition of keratin in nature-a new hypothesis of industrial relevance

Discovery of keratin-degrading enzymes from fungi and bacteria has primarily focused on finding one protease with efficient keratinase activity. Recently, an investigation was conducted of all keratinases secreted from a fungus known to grow on keratinaceous materials, such as feather, horn, and hooves. The study demonstrated that a minimum of three keratinases is needed to break down keratin, an endo-acting, an exo-acting, and an oligopeptide-acting keratinase. Further, several studies have documented that disruption of sulfur bridges of the keratin structure acts synergistically with the keratinases to loosen the molecular structure, thus giving the enzymes access to their substrate, the protein structure. With such complexity, it is relevant to compare microbial keratin decomposition with the microbial decomposition of well-studied polymers such as cellulose and chitin. Interestingly, it was recently shown that the specialized enzymes, lytic polysaccharide monoxygenases (LPMOs), shown to be important for breaking the recalcitrance of cellulose and chitin, are also found in keratin-degrading fungi. A holistic view of the complex molecular self-assembling structure of keratin and knowledge about enzymatic and boosting factors needed for keratin breakdown have been used to formulate a hypothesis for mode of action of the LPMOs in keratin decomposition and for a model for degradation of keratin in nature. Testing such hypotheses and models still needs to be done. Even now, the hypothesis can serve as an inspiration for designing industrial processes for keratin decomposition for conversion of unexploited waste streams, chicken feather, and pig bristles into bioaccessible animal feed.

Optimal culture conditions for keratinase production by a novel thermophilic Myceliophthora thermophila strain GZUIFR-H49-1

AIMS

  To investigate the effect of medium compositions and culture conditions on keratinase production by a novel thermophilic fungus Myceliophthora thermophila (Apinis) Oorschot strain GZUIFR-H49-1.

METHODS AND RESULTS

  The thermophilic strain GZUIFR-H49-1 with keratinolytic ability was characterized and identified as a strain of M. thermophila on the basis of its morphological characters and molecular analysis of ITS1-5.8S-ITS2 rDNA sequence. Among the medium compositions tested, the soluble starch (SS), urea, sodium thiosulfate and CaCl2 were the most effective C-source, N-source, S-source and mineral ion, respectively, by employing the single-factor experiment. The urea and pH value were the significant factors (P < 0·05) for the keratinase production in this experiment condition using Plackett–Burman factorial design. The conditions of keratinase production were further optimized by Box–Behnken design. Consequently, there was a 6·4-fold increase (5100 U l−1) in the keratinase activity than the initial value (800 U l−1) by this optimal process.

CONCLUSIONS

  This study indicated that the optimization design proved a useful and powerful tool for the development of optimal medium compositions and culture conditions. Myceliophthora thermophila strain GZUIFR-H49-1 was a promising fungus strain for keratinase production.

Biotechnological Aspects and Perspective of Microbial Keratinase Production

Keratinases are proteolytic enzymes predominantly active when keratin substrates are available that attack disulfide bridges in the keratin to convert them from complex to simplified forms. Keratinases are essential in preparation of animal nutrients, protein supplements, leather manufacture, textile processing, detergent formulation, feather meal processing for feed and fertilizer, the pharmaceutical and biomedical industries, and waste management. Accordingly, it is necessary to develop a method for continuous production of keratinase from reliable sources that can be easily managed. Microbial keratinase is less expensive than conventionally produced keratinase and can be obtained from fungi, bacteria, and actinomycetes. In this overview, the expansion of information about microbial keratinases and important considerations in keratinase production are discussed.

Bacillus safensis LAU 13: a new source of keratinase and its multi-functional biocatalytic applications

A newly isolated bacterium identified as Bacillus safensis based on biochemical tests and 16S rRNA analysis and its mutant variant created by exposure to ultraviolet radiation at 254 nm were investigated for keratinolytic activity. The wild-type strain produced 35.4-50.4 U/mL keratinase over a period of 120 h, while the mutant one yielded 64.4-108.5 U/mL keratinase for the same period of 120 h. The optimal conditions for the enzyme activities were pH 7.5 and 40 °C. The mutant and wild-type strain keratinases retained 59% and 54% of their activity after 12 h pretreatment at 40 °C, and 64% and 60% of their activity after 12 h at pH 7.5, respectively. The keratinases showed high substrate specificity for feathers, but low specificity for human and bovine hairs. The enzymes were activated by Na+, Ca2+, Fe2+ and Mg2+. However, while Mn2+ activated the enzyme from the mutant strain, it inhibited that of the wild type. The mutant and wild-type strain completely degraded whole chicken feathers after 6 and 9 days at 30 ± 2 °C, and also completely dehaired goat skin within 12 and 16 h, respectively, without damage to the skin. Similarly, remarkable destaining of blood-stained cloth occurred within 2-3 h. The obtained results showed an improvement in the properties of the mutant strain for use of the micro-organism or its enzyme as biocatalysts.

Optimized preparation and characterization of CLEA-lipase from cocoa pod husk

Cross-linked enzyme aggregate (CLEA) is easily prepared from crude enzyme and has many advantages to the environment and it is considered as an economic method in the context of industrial biocatalysis compared to free enzyme. In this work, a highly active and stable CLEA-lipase from cocoa pod husk (CPH) which is a by-product after removal of cocoa beans, were assayed for their hydrolytic activity and characterized under the optimum condition successfully. Face centered central composite design (FCCCD) under response surface methodology (RSM) was used to get the optimal conditions of the three significant factors (concentration of ammonium sulfate, concentration of glutaraldehyde and concentration of additive) to achieve higher enzyme activity of CLEA. From 20 runs, the highest activity recorded was around 9.407U (83% recovered activity) under the condition of using 20% saturated ammonium sulfate, 60mM glutaraldehyde as cross-linker and 0.17mM bovine serum albumin as feeder. Moreover, the optimal reaction temperature and pH value in enzymatic reaction for both crude enzyme and immobilized were found to be 45°C at pH 8 and 60°C at pH 8.2, respectively. A systematic study of the stability of CLEA and crude enzyme was taken with regards to temperature (25-60°C) and pH (5-10) value and in both factors, CLEA-lipase showed more stability than free lipase. The Km value of CLEA was higher compared to free enzyme (0.55mM vs. 0.08mM). The CLEA retained more than 60% of the initial activity after six cycles of reuse compared to free enzyme. The high stability and recyclability of CLEA-lipase from CPH make it efficient for different industrial applications.

Strategies to characterize fungal lipases for applications in medicine and dairy industry

Lipases are water-soluble enzymes that act on insoluble substrates and catalyze the hydrolysis of long-chain triglycerides. Lipases play a vital role in the food, detergent, chemical, and pharmaceutical industries. In the past, fungal lipases gained significant attention in the industries due to their substrate specificity and stability under varied chemical and physical conditions. Fungal enzymes are extracellular in nature, and they can be extracted easily, which significantly reduces the cost and makes this source preferable over bacteria. Soil contaminated with spillage from the products of oil and dairy harbors fungal species, which have the potential to secrete lipases to degrade fats and oils. Herein, the strategies involved in the characterization of fungal lipases, capable of degrading fatty substances, are narrated with a focus on further applications.

Keratinase production and biodegradation of whole chicken feather keratin by a newly isolated bacterium under submerged fermentation

A new feather-degrading bacterium PKD 5 was isolated from feather dumping soil and identified as Bacillus weihenstephanensis based on morphological and physiochemical characteristics as well as 16S rRNA gene analysis. Extracellular keratinase was produced during submerged aerobic cultivation in a medium containing chicken feather as sole carbon and energy source and supplemented with salt solutions (NaCl 5.0, MgSO₄ 1.0, K₂HPO₄ 1.0, (NH₄)₂SO₄, 2.0 g/l). The optimal conditions for keratinase production include initial pH of 7.0, inoculum size of 2% (v/v), and cultivation at 40 °C. The maximum keratinase production and keratinolytic activity of PKD 5 was achieved after 7 days of fermentation under shaking condition (120 rpm). The enzyme has found application in developing cost-effective feather by-products for feeds and fertilizers. The manuscript first time describes B. weihenstephanensis PKD 5-mediated keratinase production under submerged fermentation and whole chicken feather biodegradation.

Keratinolytic activity of purified alkaline keratinase produced by Scopulariopsis brevicaulis (Sacc.) and its amino acids profile

Sodium dodecyl sulfate-polyacrlyamide gel electrophoresis (SDS-PAGE) was used to assess the purity and molecular weight of the previously purified alkaline keratinase enzyme of Scopulariopsis brevicaulis. The enzyme was homogenous, as seen by a single band of protein, and had an apparent molecular weight of 28.5 kDa. Amino acid profile of the purified keratinase revealed that it was composed of 14 different amino acids with high proportions of glutamic acid (20.86%), alanine (14.52%), glycine (14.21%), leucine (8.59%) and serine (7.81%). The enzyme contained moderate amounts of valine (6.01%), threonine (5.58%) and phenyl alanine (5.22%). The purified enzyme of S. brevicaulis exerted a potent keratinolytic activity and was capable to hydrolyze different keratinaceous materials with highest activity on chicken feathers followed by human nails and human hair.

Enzymatic depilation of animal hide: identification of elastase (LasB) from Pseudomonas aeruginosa MCM B-327 as a depilating protease

Conventional leather processing involving depilation of animal hide by lime and sulphide treatment generates considerable amounts of chemical waste causing severe environmental pollution. Enzymatic depilation is an environmentally friendly process and has been considered to be a viable alternative to the chemical depilation process. We isolated an extracellular protease from Pseudomonas aeruginosa strain MCM B-327 with high depilation activity using buffalo hide as a substrate. This 33 kDa protease generated a peptide mass fingerprint and de novo sequence that matched perfectly with LasB (elastase), of Pseudomonas aeruginosa. In support of this data a lasB mutant of MCM B-327 strain lacked depilatory activity and failed to produce LasB. LasB heterologously over-produced and purified from Escherichia coli also exhibited high depilating activity. Moreover, reintroduction of the lasB gene to the P. aeruginosa lasB mutant via a knock-in strategy also successfully restored depilation activity thus confirming the role of LasB as the depilating enzyme.

Medium optimization for a novel 58 kDa dimeric keratinase from Bacillus licheniformis ER-15: biochemical characterization and application in feather degradation and dehairing of hides

A novel dimeric 58 kDa keratinase is reported from Bacillus licheniformis ER-15. The bacterium produced 244 U/ml keratinase in 48 h which was increased by eight fold (1962 U/ml) after medium optimization by one-variable-at-a-time and response surface methodology. Enzyme was concentrated by ultrafiltration followed by acetone precipitation and purified by gel filtration chromatography. It had subunit of 30 and 28 kDa and pI of 8.4. Enzyme was maximally active at pH 11 and 70 degrees C. It hydrolyzed various complex proteins viz. haemoglobin, feather, hooves, fibrin and meat protein. It was a thiol activated serine protease and 6.25-fold enhancement in activity was observed in presence of 5mM mercaptoethanol. Nearly 1200 U keratinase degraded 1.5 g feather in 12h at pH 8, 50 degrees C in redox free environment. This enzyme also dehaired buffalo hide within 16 h in presence of 3% Ca (OH)(2).

Processing of poultry feathers by alkaline keratin hydrolyzing enzyme from Serratia sp. HPC 1383

The present study describes the production and characterization of a feather hydrolyzing enzyme by Serratia sp. HPC 1383 isolated from tannery sludge, which was identified by the ability to form clear zones around colonies on milk agar plates. The proteolytic activity was expressed in terms of the micromoles of tyrosine released from substrate casein per ml per min (U/mL min). Induction of the inoculum with protein was essential to stimulate higher activity of the enzyme, with 0.03% feathermeal in the inoculum resulting in increased enzyme activity (45U/mL) that further increased to 90U/mL when 3d old inoculum was used. The highest enzyme activity, 130U/mL, was observed in the presence of 0.2% yeast extract. The optimum assay temperature and pH for the enzyme were found to be 60 degrees C and 10.0, respectively. The enzyme had a half-life of 10min at 60 degrees C, which improved slightly to 18min in presence of 1mM Ca(2+). Inhibition of the enzyme by phenylmethyl sulfonyl fluoride (PMSF) indicated that the enzyme was a serine protease. The enzyme was also partially inhibited (39%) by the reducing agent beta-mercaptoethanol and by divalent metal ions such as Zn(2+) (41% inhibition). However, Ca(2+) and Fe(2+) resulted in increases in enzyme activity of 15% and 26%, respectively. The kinetic constants of the keratinase were found to be 3.84 microM (K(m)) and 108.7 microM/mLmin (V(max)). These results suggest that this extracellular keratinase may be a useful alternative and eco-friendly route for handling the abundant amount of waste feathers or for applications in other industrial processes.

Production, characterization and application of keratinase from Streptomyces gulbargensis

A Streptomyces gulbargensis newly isolated, thermotolerant feather-degrading bacterial strain was investigated for its ability to produce keratinase enzyme. Maximum keratinolytic activity was observed at 45 degrees C and pH 9.0 at 120 h of incubation. Activity was completely stable (100%) between 30 and 45 degrees C and pH 7.0-9.0, respectively. Addition of starch to the growth medium affects the activity by means of increase in keratinase secretion. After seven days of cultivation, 10-fold increase (14.3 U ml(-1)) in keratinase activity was observed in the presence of 3g starch (per liter) of the medium. The enzyme was monomeric and had a molecular mass of 46 kDa. The enzyme activity was significantly inhibited by CaCl(2) and partly inhibited by EDTA, whereas, Na(2)SO(3) enhance the enzyme activity by 2.9 times more. In addition, native chicken feather was completely degraded at 96 h of incubation. The results obtained showed that newly isolated strain S. gulbargensis could be a useful in biotechnology in terms of valorization of keratin-containing wastes or in the leather industry.

Optimization of influential parameters for extracellular keratinase production by Bacillus subtilis (MTCC9102) in solid state fermentation using Horn meal--a biowaste management

A Bacillus subtilis (MTCC9102) isolate was shown to produce significant amount of keratinase under optimized conditions in solid-state fermentation using Horn meal as a substrate. Optimized value for moisture, inoculum, and aeration were found to be 100% (v/w), 50% (v/w), and 150% (w/w), respectively, and the optimum nitrogen source was peptone and carbon source was dextrose. Maximum keratinolytic activity was observed at 48 h after incubation, and the optimum age (24 h) of inoculum was significant. The influence of cultivation temperature and initial pH of the medium on keratinase production revealed the optimum values for the temperature and pH as 37 degrees C and 7, respectively. Maximum keratinase activity of the crude extract was 15,972 U/mg/ml. These results indicate that this bacterial strain shows a high biotechnological potential for keratinase production in solid-state fermentation, and use of the horn meal as the substrate can be implemented for keratinous solid wastes management.

Purification and characterization of keratinase from recombinant Pichia and Bacillus strains

The keratinase gene from Bacillus licheniformis MKU3 was cloned and successfully expressed in Bacillus megaterium MS941 as well as in Pichia pastoris X33. Compared with parent strain, the recombinant B. megaterium produced 3-fold increased level of keratinase while the recombinant P. pastoris strain had produced 2.9-fold increased level of keratinase. The keratinases from recombinant P. pastoris (pPZK3) and B. megaterium MS941 (pWAK3) were purified to 67.7- and 85.1-folds, respectively, through affinity chromatography. The purified keratinases had the specific activity of 365.7 and 1277.7 U/mg, respectively. Recombinant keratinase from B. megaterium was a monomeric protein with an apparent molecular mass of 30 kDa which was appropriately glycosylated in P. pastoris to have a molecular mass of 39 kDa. The keratinases from both recombinant strains had similar properties such as temperature and pH optimum for activity, and sensitivity to various metal ions, additives and inhibitors. There was considerable enzyme stability due to its glycosylation in yeast system. At pH 11 the glycosylated keratinase retained 95% of activity and 75% of its activity at 80 degrees C. The purified keratinase hydrolyzed a broad range of substrates and displayed effective degradation of keratin substrates. The K(m) and V(max) of the keratinase for the substrate N-succinyl-Ala-Ala-Pro-Phe-pNA was found to be 0.201 mM and 61.09 U/s, respectively. Stability in the presence of detergents, surfactants, metal ions and solvents make this keratinase suitable for industrial processes.

Keratinase production and keratin degradation by a mutant strain of Bacillus subtilis

A new feather-degrading bacterium was isolated from a local feather waste site and identified as Bacillus subtilis based on morphological, physiochemical, and phylogenetic characteristics. Screening for mutants with elevated keratinolytic activity using N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis resulted in a mutant strain KD-N2 producing keratinolytic activity about 2.5 times that of the wild-type strain. The mutant strain produced inducible keratinase in different substrates of feathers, hair, wool and silk under submerged cultivation. Scanning electron microscopy studies showed the degradation of feathers, hair and silk by the keratinase. The optimal conditions for keratinase production include initial pH of 7.5, inoculum size of 2% (v/v), age of inoculum of 16 h, and cultivation at 23 degrees C. The maximum keratinolytic activity of KD-N2 was achieved after 30 h. Essential amino acids like threonine, valine, methionine as well as ammonia were produced when feathers were used as substrates. Strain KD-N2, therefore, shows great promise of finding potential applications in keratin hydrolysis and keratinase production.

Purification and characterization of an alkaline keratinase from Streptomyces sp

A protease producing bacterial culture ('S7') was isolated from slaughterhouse waste samples, Hyderabad, India. It was related to Streptomyces sp. on the basis of biochemical properties and 16S rRNA gene sequencing. Purification of the protease present in the culture medium supernatant on sephacryl S-100 indicated that it contains a keratinase with 67% recovery, 2.5-fold purification and an estimated molecular mass of approximately 44,000 Da. Keratinase showed an optimal activity at 45 degrees C and pH 11. Keratinase activity increased substantially in presence of Ca(2+) and was inhibited in presence of PMSF and EDTA identifying it as a serine metalloprotease. Stability in the presence of detergents, surfactants and solvents make this keratinase extremely useful for biotechnological process involving keratin hydrolysis or in the leather industry.

Optimization of keratinase production and enzyme activity using response surface methodology with Streptomyces sp7

A two-step response surface methodology (RSM) study was conducted for the optimization of keratinase production and enzyme activity from poultry feather by Streptomyces sp7. Initially different combinations of salts were screened for maximal production of keratinase at a constant pH of 6.5 and feather meal concentration of 5 g/L. A combination of K2HPO4, KH2PO4, and NaCl gave a maximum yield of keratinase (70.9 U/mL) production. In the first step of the RSM study, the selected five variables (feather meal, K2HPO4, KH2PO4, NaCl, and pH) were optimized by a 25 full-factorial rotatable central composite design (CCD) that resulted in 95 U/mL of keratinase production. The results of analysis of variance and regression of a second-order model showed that the linear effects of feather meal concentration (p<0.005) and NaCl (p<0.029) and the interactive effects of all variables were more significant and that values of the quadratic effects of feather meal (p<1.72e-5), K2HPO4 (p<4.731e-6), KH2PO4 (p<1.01e-10), and pH (p 7.63e-7) were more significant than the linear and interactive effects of the process variables. In the second step, a 23 rotatable full-factorial CCD and response surface analysis were used for the selection of optimal process parameters (pH, temperature, and rpm) for keratinase enzyme activity. These optima were pH 11.0, 45 degrees C, and 300 rpm.

Characterization of an alkaline active-thiol forming extracellular serine keratinase by the newly isolated Bacillus pumilus

AIMS

The aim of the study was to optimize microbial degradation of keratinous waste and to characterize the alkaline active keratinase showing its biotechnological importance.

METHOD AND RESULTS

An extracellular keratinase enzyme was purified from the culture medium of a bacterial isolate and the conditions were optimized. The molecular weight of DEAE-Sepharose-purified keratinase was determined by SDS-PAGE. Instrumental analyses were investigated to study the mechanism of bovine hair hydrolysis. Isolate was identified as Bacillus pumilus based on phenotypic characteristics and 16S rDNA sequence. The optimized condition for its growth was pH 8 and 35 degrees C. The molecular weight of the keratinase was estimated as 65 kDa. Activity inhibition by phenyl methyl sulphonyl fluoride confirmed keratinase as serine protease type. Instrumental analysis revealed the sulphitolysis and proteolysis involved mechanism in bovine hair hydrolysis.

CONCLUSION

This study indicates that the isolated keratinase is an alkaline active serine protease with a high degree of activity towards bovine hair.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study examines a serine protease with high keratinolytic activity and degradation mechanism for bovine hair. The keratinolytic activity of the isolated strain and its reaction mechanism on bovine hair could show biotechnological potential in the leather industry.

Optimization of extracellular keratinase production by poultry farm isolate Scopulariopsis brevicaulis

A Scopulariopsis brevicaulis poultry farm isolate was chosen to study factors influencing keratinase production. The parameters were optimized by factorial design. The highest enzyme production by this fungus was obtained at pH 7.5, a temperature of 30 degrees C and a growth period of 5 weeks. The production of the enzyme was enhanced when the culture medium was supplemented with glucose (1%), sodium nitrate (2%), feather (1.5%) and CaCl(2) (1 mM). According to the responses from the experimental design, the effects of each variable were calculated, and the interactions between them were determined. The experimental values were found to be in accordance with the predicted values, the correlation coefficient is 0.9978.

Secretion of keratinolytic enzymes and keratinolysis by Scopulariopsis brevicaulis and Trichophyton mentagrophytes: regression analysis

A survey on keratinophilic fungi from poultry-farm soils at Namakkal and from feather dumping soils at Chennai, India, revealed the existence of 34 species of fungi. Most of the fungi exhibited variable efficiency in producing extracellular keratinase when grown in plates with chicken feathers as the sole carbon and nitrogen source. The fungi Aspergillus flavus, Aspergillus niger, Aspergillus versicolor, Chrysosporium state of Arthroderma tuberculatum, Paecilomyces carneus, Scopulariopsis brevicaulis, Trichoderma viride, and Trichophyton mentagrophytes were efficient candidates to degrade the feathers. However, when cultivating the strains in submerged conditions in a medium containing chicken feathers as the sole nutrients source, Aspergillus glaucus, Chrysosporium keratinophilum, Curvularia lunata, Fusarium solani, and Penicillium citrinum also proved to be potent. Among all species, S. brevicaulis and Trichophyton mentagrophytes produced higher amounts of keratinase in both methods. Conditions for keratinase production were optimized by statistical design and surface plots. The highest keratinase activity was estimated by S. brevicaulis (3.2 KU/mL) and Trichophyton mentagrophytes (2.7 KU/mL) in the culture medium with chicken feathers and shows (79% and 72.2% of degrading ability, respectively).

Microbial keratinases and their prospective applications: an overview

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.