Extraction of keratin from waste chicken feathers using sodium sulfide and l-cysteine

Microbial disintegration of wool: An effective and sustainable approach for keratin extraction

Keratin is an important biopolymer used to develop biomaterials for biomedical and industrial applications. Traditional keratin extraction methods involve the removal of surface lipids using organic solvents, detergents, and energy-intensive processes that often compromise the purity of the extracted keratin. In the present study, wool fibers were microbially disintegrated to isolate cortical cells, achieving a maximum yield of 61.43 % ± 2.02 % at a wool concentration of 3.5 % (w/v). The average length and diameter of the cortical cells were 93.50 ± 5.11 μm and 3.93 ± 0.36 μm, respectively. This microbial process effectively removed surface lipids and cuticle proteins, making it suitable for keratin extraction. The extracted keratin was characterized using FT-IR and XRD, confirming the presence of characteristic chemical groups. Thermal stability, assessed through DSC and TGA, demonstrated the stability of cortical cells. Secondary structure analysis revealed the presence of both α-helix and β-sheet conformations. The molecular weight of the extracted keratin was determined to be between 35 and 63 kDa, with two distinct protein bands. Additionally, the extracted keratin exhibited biocompatibility with NIH3T3 cell lines. This method provides a sustainable approach to isolating pure keratin from wool cortex for biomaterial development.

Unlocking the Potential of Keratin: A Comprehensive Exploration from Extraction and Structural Properties to Cross-Disciplinary Applications

The rapid expansion of the livestock and poultry industry has led to a considerable increase in slaughter byproducts; however, exploring their potential applications still needs to be improved. These underutilized byproducts, which include nails, hides, skins, and bones, represent a significant loss of valuable biological resources. Among these materials, keratin has garnered considerable attention due to its unique properties as a natural biopolymer. Keratin exhibits outstanding mechanical properties and biocompatibility and has attracted increasing attention for its recovery and conversion into relevant application materials. However, natural keratin typically has a high sulfur content, complex 3D structure, and abundant hydrogen and disulfide bonds, which cause challenges in application. Current extraction for keratin includes physical, chemical, biological, and hybrid approaches. Combining multiple methods synergistically enhances protein extraction efficiency and purity, and facilitates the exploration of structure and functional properties. This review encompasses the structural characteristics, properties, extraction methods, and research progress related to keratin. The preparation and application of keratin composite materials in different forms, such as fibers, films, hydrogels, and scaffolds, are illustrated. Applications in several fields, including biomedicine, flexible electronic components, environmental materials and food packaging are discussed. Hopefully, this paper will provide a comprehensive understanding and guidance for further development and application of keratin materials.

Recovery of keratin from feather meal: a new route to valorize an agro-industrial co-product

The valorization of agro-industrial by-products/co-products represents a sustainable pathway to produce high-value biomaterials. Feather meal is an agro-industrial co-product derived from clean and undecomposed poultry feathers processed under high heat and pressure that offers an economically viable and scalable alternative for keratin extraction compared to native feathers. This study explores the recovery of keratin from feather meal through an optimized alkaline hydrolysis process, achieving a yield of 20 wt.% at 15°C and 90 min of extraction by using 2 mol L-1 sodium hydroxide solution. A negative temperature dependence was observed in keratin extraction yield, suggesting the occurrence of thermal degradation at elevated temperatures. Protein analyses by different techniques confirmed the characteristic diffraction peaks, functional groups, and elemental composition (carbon, nitrogen, oxygen, and sulphur) of feather keratin. The extracted keratin presented a low molar mass of 9 kg mol-1. Considering the circular economy principles, this work proposes a novel valorization route for feather meal and highlights its potential in creating value-added materials for several applications in medicine, pharmaceuticals, and engineering areas.

Enhanced Delivery of Biomolecules into Caco2 Cells Based on the Cell-Penetrating Ability of Keratin Peptides

Keratin, as a promising bioresource, possesses significant potential for diverse biological applications due to its favorable biocompatibility, low toxicity, biodegradability, and cell adhesion ability. However, there are few studies on the cell-penetrating ability of keratin peptides (KEPs) for biomolecule delivery. Therefore, this study explored the cell-penetrating ability of KEPs with different molecular weights (Mw) on Caco2 cells using fluorescein-labeled insulin (FITC-INS) as the target intracellular biomolecule. The potential cell-penetrating mechanism was elaborated by combining cellular investigation with the physicochemical characterization of KEPs. The result shows that the KEPs <3 kDa (KEP1) exhibited the highest cell-penetrating ability at 2 mg/mL, allowing efficient delivery of FITC-INS into Caco2 cells without covalent bonding. The cellular uptake mechanism was energy-dependent, mainly involving macropinocytosis. The further fractionation of KEP1 reveals that the most effective components consisted of 8-19 amino acids, including specific hydrophobic peptides (e.g., RVVIEPSPVVV and IIIQPSPVVV), PPII amphipathic peptides (e.g., PPPVVVTFP and FIQPPPVVV), and Cys-rich peptides (e.g., LCAPTPCGPTPL and CLPCRPCGPTPL). Additionally, analysis of the secondary and tertiary structure and amino acid composition illustrated that KEP1 exhibited rich hydrophobic residues and disulfide bonds, which probably contributed to its cell-penetrating ability, as opposed to its small particle size and electrostatic interactions. This study reveals the cell-penetrating ability of KEPs, thus highlighting their potential as biomaterials for noncovalently delivering biomolecules.

Keratin hydrolysate as a chrome exhaust aid and keratin filler in leather processing: A cleaner technology approach for tannery solid waste management and leather manufacturing

Hair burning unhairing and dampening of tannery wastes during the hair-saving unhairing process are becoming significant problems in the tanning industry. Therefore, this research article focuses on the extraction of keratin hydrolysate (KH) and its application as a chrome exhaust aid and keratin filler in leather manufacturing process. The structure, morphology and functional groups of the extract were examined using X-Ray Diffractometer (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR), respectively. To study and contrast the degree of improvement in chromium uptake, the KH solution was applied both before tanning on the pickled pelt and after tanning during basification. The thermal stability, physical strength characteristics and organoleptic properties of the leathers obtained were characterized. Furthermore, the environmental impact of the tanning system was assessed through a comparative analysis of the spent liquors. Finally, experimental retanning process was conducted to replace the commercial protein filler (Celatan F: 50, 75, and 100 %) with KH solution, with concurrent processing of control leather using conventional chrome tanning agent at 6 % dosage of chromium. The FTIR analysis of the extract confirmed the presence of alkyl side chains of amino acids as well as carboxylic, amide, carboxyl group and aldehyde functional groups at 1400-1700 cm-1,3,303.46 cm-1,3270 cm-1 and 2752 cm-1, respectively. XRD spectrum showed two diffraction peaks at 2 theta values of 9.36° and 21.16°, respectively. Leathers with improved mechanical strength, organoleptic properties and thermal stability were obtained with 100 % substitution of Celatan F at pH 6 and 10 % chromium dosage. It was also discovered that the shrinkage temperature of the experimental leather was enhanced to more than 105 °C. Environmental impact evaluation on the spent liquor showed that the complete replacement of Celatan F with KH solution brought about a notable decrease in COD and TDS in the spent liquor. The extraction and application of tannery hair waste-based keratin hydrolysate as an efficient, environmentally friendly chrome exhaust aid and keratin filler has been attempted and established in this research article.

Morphological, Thermal, and Mechanical Properties of Nanocomposites Based on Bio-Polyamide and Feather Keratin-Halloysite Nanohybrid

One solution to comply with the strict regulations of the European Commission and reduce the environmental footprint of composites is the use of composite materials based on bio-polymers and fillers from natural resources. The aim of our work was to obtain and analyze the properties of bio-polymer nanocomposites based on bio-PA (PA) and feather keratin-halloysite nanohybrid. Keratin (KC) was mixed with halloysite (H) as such or with the treated surface under dynamic conditions, resulting in two nanohybrids: KCHM and KCHE. The homogenization of PA with the two nanohybrids was conducted using the extrusion processing process. Two types of nanocomposites, PA-KCHM and PA-KCHE, with 5 wt.% KC and 1 wt.% H were obtained. The properties were analyzed using SEM, XRD, FTIR, RAMAN, TGA, DSC, tensile/impact tests, DMA, and nanomechanical tests. The best results were obtained for PA-KCHE due to the stronger interaction between the components and the uniform dispersion of the nanohybrid in the PA matrix. Improvements in the modulus of elasticity and of the surface hardness by approx. 75% and 30%, respectively, and the resistance to scratch were obtained. These results are promising and constitute a possible alternative to synthetic polymer composites for the automotive industry.

Turning Food Protein Waste into Sustainable Technologies

For each kilogram of food protein wasted, between 15 and 750 kg of CO2 end up in the atmosphere. With this alarming carbon footprint, food protein waste not only contributes to climate change but also significantly impacts other environmental boundaries, such as nitrogen and phosphorus cycles, global freshwater use, change in land composition, chemical pollution, and biodiversity loss. This contrasts sharply with both the high nutritional value of proteins, as well as their unique chemical and physical versatility, which enable their use in new materials and innovative technologies. In this review, we discuss how food protein waste can be efficiently valorized not only by reintroduction into the food chain supply but also as a template for the development of sustainable technologies by allowing it to exit the food-value chain, thus alleviating some of the most urgent global challenges. We showcase three technologies of immediate significance and environmental impact: biodegradable plastics, water purification, and renewable energy. We discuss, by carefully reviewing the current state of the art, how proteins extracted from food waste can be valorized into key players to facilitate these technologies. We furthermore support analysis of the extant literature by original life cycle assessment (LCA) examples run ad hoc on both plant and animal waste proteins in the context of the technologies considered, and against realistic benchmarks, to quantitatively demonstrate their efficacy and potential. We finally conclude the review with an outlook on how such a comprehensive management of food protein waste is anticipated to transform its carbon footprint from positive to negative and, more generally, have a favorable impact on several other important planetary boundaries.

Valorization of feather waste in Brazil: structure, methods of extraction, and applications of feather keratin

This systematic review presents the potential of using feather waste as a β-keratin source, including the Brazilian scenario in the generation of this byproduct. The structure and properties of α- and β-keratin, the methods commonly reported to extract keratin from poultry feathers, and applications of feather keratin-based materials are also covered in this review. The literature search for poultry production data in Brazil was conducted for the last 2 years, for the period 2021-2022. A broad literature search for extraction methods and applications of feather keratin was done for the period 2001-2022. The poultry industry is one of the largest sectors of the food industry, and Brazil was the third-largest world producer of chicken meat with more than six billion chickens slaughtered in 2021. Poultry feathers constitute about 7% weight of broilers; thus, it can be estimated that about one million tons of poultry feathers were generated in Brazil in 2021, and the improper disposal of this byproduct contributes to environmental problems and disease transmission. The most common method of reusing feathers is the production of feather meal. From economic and environmental points of view, it is advantageous to develop processes to add value to this byproduct, including the extraction of keratin. Among natural biodegradable polymers, keratin-based materials have revolutionized the field of biomaterials due to their biocompatibility and biodegradability, allowing their application in biomedical, pharmaceutical, chemical, and engineering areas.

Wool keratin as a novel alternative protein: A comprehensive review of extraction, purification, nutrition, safety, and food applications

The growing global population and lifestyle changes have increased the demand for specialized diets that require protein and other essential nutrients for humans. Recent technological advances have enabled the use of food bioresources treated as waste as additional sources of alternative proteins. Sheep wool is an inexpensive and readily available bioresource containing 95%-98% protein, making it an outstanding potential source of protein for food and biotechnological applications. The strong structure of wool and its indigestibility are the main hurdles to achieving its potential as an edible protein. Although various methods have been investigated for the hydrolysis of wool into keratin, only a few of these, such as sulfitolysis, oxidation, and enzymatic processes, have the potential to generate edible keratin. In vitro and in vivo cytotoxicity studies reported no cytotoxicity effects of extracted keratin, suggesting its potential for use as a high-value protein ingredient that supports normal body functions. Keratin has a high cysteine content that can support healthy epithelia, glutathione synthesis, antioxidant functions, and skeletal muscle functions. With the recent spike in new keratin extraction methods, extensive long-term investigations that examine prolonged exposure of keratin generated from these techniques in animal and human subjects are required to ascertain its safety. Food applications of wool could improve the ecological footprint of sheep farming and unlock the potential of a sustainable protein source that meets demands for ethical production of animal protein.

Preparation Methods and Functional Characteristics of Regenerated Keratin-Based Biofilms

The recycling, development, and application of keratin-containing waste (e.g., hair, wool, feather, and so on) provide an important means to address related environmental pollution and energy shortage issues. The extraction of keratin and the development of keratin-based functional materials are key to solving keratin-containing waste pollution. Keratin-based biofilms are gaining substantial interest due to their excellent characteristics, such as good biocompatibility, high biodegradability, appropriate adsorption, and rich renewable sources, among others. At present, keratin-based biofilms are a good option for various applications, and the development of keratin-based biofilms from keratin-containing waste is considered crucial for sustainable development. In this paper, in order to achieve clean production while maintaining the functional characteristics of natural keratin as much as possible, four important keratin extraction methods—thermal hydrolysis, ultrasonic technology, eco-friendly solvent system, and microbial decomposition—are described, and the characteristics of these four extraction methods are analysed. Next, methods for the preparation of keratin-based biofilms are introduced, including solvent casting, electrospinning, template self-assembly, freeze-drying, and soft lithography methods. Then, the functional properties and application prospects of keratin-based biofilms are discussed. Finally, future research directions related to keratin-based biofilms are proposed. Overall, it can be concluded that the high-value conversion of keratin-containing waste into regenerated keratin-based biofilms has great importance for sustainable development and is highly suggested due to their great potential for use in biomedical materials, optoelectronic devices, and metal ion detection applications. It is hoped that this paper can provide some basic information for the development and application of keratin-based biofilms.

Wool Keratin Nanoparticle-Based Micropatterns for Cellular Guidance Applications

The waste stream of low-grade wool is an underutilized source of keratin-rich materials with appropriate methods for upcycling into high value-added products still being an open challenge. In the present work, keratins were precipitated from their water solution to produce hierarchical keratin particles via isoelectric precipitation. Matrix-assisted laser desorption/ionization coupled with time-of-flight tandem mass spectrometry analysis (MALDI-TOF/TOF MS/MS) showed the presence of the amino acid sequence leucine-aspartic acid-valine (LDV) in the extracted keratin. This well-known cell adhesion motif is recognized by the cell adhesion molecule α₄β₁ integrin. We showed that keratin particles had this tripeptide exposed on the surface and that it could be leveraged, via patterns obtained with microcontact printing, to support and facilitate dermal fibroblast cell adhesion and direct their growth orientation. The zeta potential, isoelectric point, morphological structures, chemical composition, and biocompatibility of keratin particles and the influence of the surfactant sodium dodecyl sulfate (SDS) were investigated. An appropriate ink for microcontact printing of the keratin particles was developed and micron-sized patterns were obtained. Cells adhered preferentially to the patterns, showing how this strategy could be used to functionalize biointerfaces.

Electrospun non-wovens potential wound dressing material based on polyacrylonitrile/chicken feathers keratin nanofiber

Electrospinning nanofibers have a tremendous interest in biomedical applications such as tissue engineering, drug administration, and wound healing because of their ability to replicate and restore the function of the natural extracellular matrix found in tissues. The study’s highlight is the electrospinning preparation and characterization of polyacrylonitrile with chicken feather keratin as an additive. In this study, keratin was extracted from chicken feather waste using an environmentally friendly method and used to reinforce polymeric nanofiber mats. Scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy were used to examine the morphology and the structure of the prepared nanofiber mats. The effect of keratin on the porosity and the tensile strength of reinforcing nanofibers is investigated. The porosity ratio of the nanofiber mats goes up from 24.52 ± 2.12 for blank polyacrylonitrile (PAN (NF)) to 90.89 ± 1.91% for polyacrylonitrile nanofiber with 0.05 wt% keratin (PAN/0.05% K). Furthermore, keratin reinforcement improves the nanofiber's mechanical properties, which are important for wound dressing application, as well as its antibacterial activity without causing hemolysis (less than 2%). The best antibacterial activities were observed against Pseudomonas aeruginosa (30 ± 0.17 mm inhibition zone) and Staphylococcus aureus (29 ± 0.31 mm inhibition zone) for PAN/0.05% K sample, according to the antibacterial test. This research has a good potential to broaden the use of feather keratin-based nanofibers in wound healing.

High-expression and characterization of a novel serine protease from Ornithinibacillus caprae L9T with eco-friendly applications

In the current work, a novel thermophilic serine protease gene (P3862) from Ornithinibacillus caprae L9^T was functionally expressed in Bacillus subtilis SCK6. The monomeric enzyme of about 29 kDa was purified to homogeneity with 43.91% of recovery and 2.81-folds of purification. Characterization of the purified protease revealed the optimum activity at pH 7 and 65 °C. The protease exhibited excellent activity and stability in the presence of Na⁺, Mg²⁺, Ca²⁺, ethanediol, n-hexane, Tween-20, Tween-80 and Triton X-100. P3862 displayed favorable caseinolytic activity, moderate keratinolytic activity but no collagenolytic activity. Besides, the homology model of P3862 possessed a globular configuration and characteristic of α/β hydrolase fold, and displayed stable interactions with casein, glycoprotein and keratin rather than collagen. Moreover, the crude enzyme could completely dehair goatskin within 6 h, resulting in decrease in BOD₅, COD and TSS loads by 72.86, 74.07, and 73.79%, respectively, as compared with Na₂S treatment. Biocatalytic applications revealed that it could effectively remove egg-stains from fabrics at 37 °C for 30 min with low supplementation (300 U/mL), and was able to degrade the feathers of duck and chicken. Overall, these outstanding properties make P3862 valuable in the development of environmentally friendly biotechnologies .

Slaughterhouse and poultry wastes: management practices, feedstocks for renewable energy production, and recovery of value added products

The slaughterhouse and poultry industry is possibly one of the fastest-growing sectors driven by the increasing demand in food availability. Subsequently, the wastes produced from the slaughterhouse and poultry industry are in huge quantities, which could be a promising resource for the recovery of value added products, and bioenergy production to minimize the dependence on fossil fuels. Furthermore, the wastes from slaughterhouses and poultry are a hub of pathogens that is capable of infecting humans and animals. This demands the emerging need for an effective and safe disposal method to reduce the spread of diseases following animal slaughtering. In light of that, the state of the production of slaughterhouse and poultry wastes was presented at first. Following this, the impact of solid waste exposure in terms of air, water, and soil pollution and the associated health challenges due to improper solid waste management practices were presented to highlight the importance of the topic. Secondly, the potency of these solid wastes and the various waste-to-energy technologies that have been employed for effective management and resource utilization of wastes generated from slaughterhouses and poultry were reviewed in detail. Finally, this review also highlights the opportunities and challenges associated with effective solid waste management, future requirements for the development of effective technologies for the recovery of value added products (like keratin, fibreboards), and biofuel production.

Molecular Identification of Keratinase DgokerA from Deinococcus gobiensis for Feather Degradation

Keratin is a tough fibrous structural protein that is difficult to digest with pepsin and trypsin because of the presence of a large number of disulfide bonds. Keratin is widely found in agricultural waste. In recent years, especially, the development of the poultry industry has resulted in a large accumulation of feather keratin resources, which seriously pollute the environment. Keratinase can specifically attack disulfide bridges in keratin, converting them from complex to simplified forms. The keratinase thermal stability has drawn attention to various biotechnological industries. It is significant to identify keratinases and improve their thermostability from microorganism in extreme environments. In this study, the keratinases DgoKerA was identified in Deinococcus gobiensis I-0 from the Gobi desert. The amino acid sequence analysis revealed that DgoKerA was 58.68% identical to the keratinase MtaKerA from M. thermophila WR-220 and 40.94% identical to the classical BliKerA sequence from B. licheniformis PWD-1. In vitro enzyme activity analysis showed that DgoKerA exhibited an optimum temperature of 60 °C, an optimum pH of 7 and a specific enzyme activity of 51147 U/mg. DgoKerA can degrade intact feathers at 60 °C and has good potential for industrial applications. The molecular modification of DgoKerA was also carried out using site-directed mutagenesis, in which the mutant A350S enzyme activity was increased by nearly 30%, and the results provide a theoretical basis for the development and optimization of keratinase applications.

A Novel Thermostable Keratinase from Deinococcus geothermalis with Potential Application in Feather Degradation

Keratinase can specifically attack disulfide bridges in keratin to convert them from complex to simplified forms. Keratinase thermal stability has drawn attention to various biotechnological industries. In this study, a keratinase DgeKer was identified from a slightly thermophilic species, D. geothermalis. The in silico analysis showed that DgeKer is composed of signal peptide, N-terminal propeptide, mature domain, and C-terminal extension. DgeKer and its C-terminal extension-truncated enzyme (DgeKer-C) were cloned and expressed in E. coli. The purified DgeKer and DgeKer-C showed maximum activity at 70 °C and pH 9–The thermal stability assay (60 °C) showed that the half-life value of DgeKer and DgeKer-C were 103.45 min and 169.10 min, respectively. DgeKer and DgeKer-C were stable at the range of pH from 9 to 11 and showed good tolerance to some metal ions, surfactants and organic solvent. Furthermore, DgeKer could degrade feathers at 70 °C for 60 min. However, the medium became turbid with obvious softening of barbules after being treated with DgeKer-C, which might be due to C-terminal extension. In summary, a thermostable keratinase DgeKer with high efficiency degradation of feathers may have great potential in industry.

Keratin particles generated from rapid hydrolysis of waste feathers with green DES/KOH: Efficient adsorption of fluoroquinolone antibiotic and its reuse

Fluoroquinolone antibiotics are widely used in human and veterinary medicine. However, untreated fluoroquinolone seriously threatens the ecosystem and human health. In this study, deep eutectic solvents (DESs) were applied for the hydrolysis of waste feathers, and the keratin particles (KPs) in a low-cost teabag were utilized to adsorb fluoroquinolone norfloxacin. Results showed that choline chloride/ethylene glycol DES rapidly hydrolyzed feathers within 10 min, and the undissolved particles effectively adsorbed norfloxacin. Adding KOH markedly shortened the hydrolysis time (6 min) and increased the adsorption ability of KPs. The optimum hydrolysis conditions were DES ratio of 1 g: 4.67 g, KOH of 35.68 g L^-1, and temperature of 90 °C. When KP_DES+KOH of 2 g L^-1, norfloxacin of 25 mg L^-1, and pH₀ 7 were used, 94% of norfloxacin was removed in 60 min. A low-cost teabag effectively separated the KPs from the solution after adsorption and did not decrease the adsorption ability of the KPs. The Langmuir isotherm model well described the adsorption behavior of KPs_DES+KOH (q_max = 79.36 mg g^-1, R² = 0.9972). In addition, acetone efficiently regenerated the exhausted KPs_DES+KOH. The KPs maintained >80% of its adsorption ability after seven cycles of regeneration.

Recent progress in the conversion of biomass wastes into functional materials for value-added applications

The amount of biomass wastes is rapidly increasing, which leads to numerous disposal problems and governance issues. Thus, the recycling and reuse of biomass wastes into value-added applications have attracted more and more attention. This paper reviews the research on biomass waste utilization and biomass wastes derived functional materials in last five years. The recent research interests mainly focus on the following three aspects: (1) extraction of natural polymers from biomass wastes, (2) reuse of biomass wastes, and (3) preparation of carbon-based materials as novel adsorbents, catalyst carriers, electrode materials, and functional composites. Various biomass wastes have been collected from agricultural and forestry wastes, animal wastes, industrial wastes and municipal solid wastes as raw materials with low cost; however, future studies are required to evaluate the quality and safety of biomass wastes derived products and develop highly feasible and cost-effective methods for the conversion of biomass wastes to enable the industrial scale production.

Efficient keratinase expression via promoter engineering strategies for degradation of feather wastes

Keratinases are promising alternatives over ordinary proteases in several industrial applications due to their unique properties compared with their counterparts in the protease categories. However, their large-scale industrial application is limited by the low expression and poor fermentation efficiency of keratinase. Here, we demonstrate that the expression level of keratinase can be improved by constructing a more efficient enzyme expression system hereby enables the highest production titer as regarding recombinant keratinase production to date. Specially, ten promoters were evaluated and the aprE promoter exhibits a significant promotion of keratinase (kerBv) titer from 165 U/mL to 2605 U/mL in Bacillus subtilis. The batch fermentation mode resulted in a maximum keratinase activity of 7176 U/mL at 36 h in a 5-L fermenter. Furthermore, the extracellular keratinase activity attained up to 16,860 U/mL via fed-batch fermentation within 30 h. The combination of keratinase with l-cysteine brings about 66.4 % degree of degradation of feather. Our work provides a new insight into the development of efficient keratinase fermentation processes with B. subtilis cell factory.