Keratinase production and biodegradation of polluted secondary chicken feather wastes by a newly isolated multi heavy metal tolerant bacterium-Alcaligenes sp. AQ05-001

Keratin-PNIPAM Hybrid Microgels: Preparation, Morphology and Swelling Properties

Combinations of synthetic polymers, such as poly(N-isopropylacrylamide) (PNIPAM), with natural biomolecules, such as keratin, show potential in the field of biomedicine, since these hybrids merge the thermoresponsive properties of PNIPAM with the bioactive characteristics of keratin. This synergy aims to produce hybrids that can respond to environmental stimuli while maintaining biocompatibility and functionality, making them suitable for various medical and biotechnological uses. In this study, we exploit keratin derived from wool waste in the textile industry, extracted via sulfitolysis, to synthesize hybrids with PNIPAM microgel. Utilizing two distinct methods-polymerization of NIPAM with keratin (HYB-P) and mixing preformed PNIPAM microgels with keratin (HYB-M)-resulted in hybrids with 20% and 25% keratin content, respectively. Dynamic light scattering (DLS) and transmission electron microscopic (TEM) analyses indicated the formation of colloidal systems with particle sizes of around 110 nm for HYB-P and 518 nm for HYB-M. The presence of keratin in both systems, 20% and 25%, respectively, was confirmed by spectroscopic (FTIR and NMR) and elemental analyses. Distinct structural differences were observed between HYB-P and HYB-M, suggesting a graft copolymer configuration for the former hybrid and a complexation for the latter one. Furthermore, these hybrids demonstrated temperature responsiveness akin to PNIPAM microgels and pH responsiveness, underscoring their potential for diverse biomedical applications.

Transcriptomics Reveals the Mechanism of Purpureocillium lilacinum GZAC18-2JMP in Degrading Keratin Material

Microbial degradation of keratin is characterized by its inherent safety, remarkable efficiency, and the production of copious degradation products. All these attributes contribute to the effective management of waste materials at high value-added and in a sustainable manner. Microbial degradation of keratin materials remains unclear, however, with variations observed in the degradation genes and pathways among different microorganisms. In this study, we sequenced the transcriptome of Purpureocillium lilacinum GZAC18-2JMP mycelia on control medium and the medium containing 1% feather powder, analyzed the differentially expressed genes, and revealed the degradation mechanism of chicken feathers by P. lilacinum GZAC18-2JMP. The results showed that the chicken feather degradation rate of P. lilacinum GZAC18-2JMP reached 64% after 216 h of incubation in the fermentation medium, reaching a peak value of 148.9 μg·mL-1 at 192 h, and the keratinase enzyme activity reached a peak value of 211 U·mL-1 at 168 h, which revealed that P. lilacinum GZAC18-2JMP had a better keratin degradation effect. A total of 1001 differentially expressed genes (DEGs) were identified from the transcriptome database, including 475 upregulated genes and 577 downregulated genes. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis of the DEGs revealed that the metabolic pathways related to keratin degradation were mainly sulfur metabolism, ABC transporters, and amino acid metabolism. Therefore, the results of this study provide an opportunity to gain further insight into keratin degradation and promote the biotransformation of feather wastes.

Bacillus velezensis strain NA16 shows high poultry feather-degrading efficiency, protease and amino acid production

Isolated Bacillus velezensis strain NA16, which produces proteases, amino acids and the transcription levels of different keratinolytic enzymes and disulfide reductase genes in whole gene sequencing, was evaluated during feather degradation. The result shows under optimum fermentation conditions, chicken feather fermentation showed total amino acid concentration of 7599 mg/L, degradation efficiency of 99.3% at 72 h, and protease activity of 1058 U/mL and keratinase activity of 288 U/mL at 48 h. Goose feather fermentation showed total amino acid concentration of 4918 mg/L (96 h), and degradation efficiency was 98.9% at 120 h. Chicken feather fermentation broth at 72 h showed high levels of 17 amino acids, particularly phenylalanine (1050 ± 1.90 mg/L), valine (960 ± 1.04 mg/L), and glutamic (950 ± 3.00 mg/L). Scanning electron microscopy and Fourier transform infrared analysis revealed the essential role of peptide bond cleavage in structural changes and degradation of feathers. Protein purification and zymographic analyses revealed a key role in feather degradation of the 39-kDa protein encoded by gene1031, identified as an S8 family serine peptidase. Whole genome sequencing of NA16 revealed 26 metalloproteinase genes and 22 serine protease genes. Among the proteins, S8 family serine peptidase (gene1031, gene1428) and S9 family peptidase (gene3132) were shown by transcription analysis to play major roles in chicken feather degradation. These findings revealed the transcription levels of different families of keratinolytic enzymes in the degradation of feather keratin by microorganisms, and suggested potential applications of NA16 in feather waste management and amino acid production.

A Comparative Transcriptome Analysis Unveils the Mechanisms of Response in Feather Degradation by Pseudomonas aeruginosa Gxun-7

Microbial degradation of feathers offers potential for bioremediation, yet the microbial response mechanisms warrant additional investigation. In prior work, Pseudomonas aeruginosa Gxun-7, which demonstrated robust degradation of feathers at elevated concentrations, was isolated. However, the molecular mechanism of this degradation remains only partially understood. To investigate this, we used RNA sequencing (RNA-seq) to examine the genes that were expressed differentially in P. aeruginosa Gxun-7 when exposed to 25 g/L of feather substrate. The RNA-seq analysis identified 5571 differentially expressed genes; of these, 795 were upregulated and 603 were downregulated. Upregulated genes primarily participated in proteolysis, amino acid, and pyruvate metabolism. Genes encoding proteases, as well as those involved in sulfur metabolism, phenazine synthesis, and type VI secretion systems, were notably elevated, highlighting their crucial function in feather decomposition. Integration of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) taxonomies, combined with a review of the literature, led us to propose that metabolic feather degradation involves environmental activation, reducing agent secretion, protease release, peptide/amino acid uptake, and metabolic processes. Sulfite has emerged as a critical activator of keratinase catalysis, while cysteine serves as a regulatory mediator. qRT-PCR assay results for 11 selected gene subset corroborated the RNA-seq findings. This study enhances our understanding of the transcriptomic responses of P. aeruginosa Gxun-7 to feather degradation and offers insights into potential degradation mechanisms, thereby aiding in the formulation of effective feather waste management strategies in poultry farming.

Sustainable valorizing high-protein feather waste utilization through solid-state fermentation by keratinase-enhanced Streptomyces sp. SCUT-3 using a novel promoter

Feather waste, a rich source of proteins, has traditionally been processed through high-temperature puffing and acid-base hydrolysis, contributing to generation of greenhouse gases and H2S. To address this issue, we employed circular economy techniques to recover the nutritional value of feather waste. Streptomyces sp. SCUT-3, an efficient proteolytic and chitinolytic bacterium, was isolated for feather degradation previously. This study aimed to valorize feather waste for feed purposes by enhancing its feather transformation ability through promoter optimization. Seven promoters were identified through omics analysis and compared to a common Streptomyces promoter ermE*p. The strongest promoter, p24880, effectively enhanced the expression of three candidate keratinases (Sep39, Sep40, and Sep53). The expression efficiency of double-, triple-p24880 and sandwich p24880-sep39-p24880 promoters were further verified. The co-overexpression strain SCUT-3-p24880-sep39-p24880-sep40 exhibited a 16.21-fold increase in keratinase activity compared to the wild-type. Using this strain, a solid-state fermentation process was established that increased the feather/water ratio (w/w) to 1:1.5, shortened the fermentation time to 2.5 days, and increased soluble peptide and free amino acid yields to 0.41 g/g and 0.14 g/g, respectively. The resulting has high protein content (90.49 %), with high in vitro digestibility (94.20 %). This method has the potential to revolutionize the feather waste processing industry.

Effective biodegradation on chicken feather by the recombinant KerJY-23 Bacillus subtilis WB600: A synergistic process coupled by disulfide reductase and keratinase

Keratin wastes are abundantly available but rich in hard-degrading fibrous proteins, and the keratinase-producing microorganisms have gained significant attention due to their biodegradation ability against keratinous materials. In order to improve the degradation efficiency of feather keratins, the keratinase gene (kerJY-23) from our previously isolated feather-degrading Ectobacillus sp. JY-23 was overexpressed in Bacillus subtilis WB600 strain. The recombinant KerJY-23 strain degraded chicken feathers rapidly within 48 h, during which the activities of disulfide reductase and keratinase KerJY-23 were sharply increased, and the free amino acids especially the essential phenylalanine and tyrosine were significantly accumulated in feather hydrolysate. The results of structural characterizations including scanning electron microscopy, Fourier transform infrared spectrum, X-ray diffraction, and X-ray photoelectron spectroscopy, demonstrated that the feather microstructure together with the polypeptide bonds and SS bonds in feather keratins were attacked and destroyed by the recombinant KerJY-23 strain. Therefore, the recombinant KerJY-23 strain contributed to feather degradation through the synergistic action of the secreted disulfide reductase to break the SS bonds and keratinase (KerJY-23) to hydrolyze the polypeptide bonds in keratins. This study offers a new insight into the underlying mechanism of keratin degradation, and provides a potential recombinant strain for the valorization of keratin wastes.

Characterization of bacterial diversity and capacity to remove lead of a consortium from mining soil

INTRODUCTION

At present, the presence of lead (Pb2+) continues to be a problem in water bodies due to its continuous use and high toxicity. The aim of this study was to investigate the bacterial diversity of a potential consortium used as a biosorbent for the removal of lead in an aqueous solution.

METHODS

The minimum inhibitory concentration and the mean lethal dose of the consortium were determined, and then the optimal variables of pH and temperature for the removal process were obtained. With the optimal conditions, the kinetic behavior was evaluated, and adjustments were made to different mathematical models. A Fourier transform infrared spectroscopy analysis was performed to determine the functional groups of the biomass participating in the removal process, and the diversity of the bacterial consortium was evaluated during Pb2+ removal by an Ion Torrent Personal Genome Machine System.

RESULTS

It was found that the intraparticle diffusion model was the one that described the adsorption kinetics showing a higher rate constant with a higher concentration of Pb2+, while the Langmuir model was that explained the isotherm at 35 °C, defining a maximum adsorption load for the consortium of 54 mg/g. In addition, it was found that Pb2+ modified the diversity and abundance of the bacterial consortium, detecting genera such as Pseudomonas, Enterobacter, Citrobacter, among others.

CONCLUSIONS

Thus, it can be concluded that the bacterial consortium from mining soil was a biosorbent with the ability to tolerate high concentrations of Pb2+ exposure. The population dynamics during adsorption showed enrichment of Proteobacteria phyla, with a wide range of bacterial families and genera capable of resisting and removing Pb2+ in solution.

Isolation of a novel feather-degrading Ectobacillus sp. JY-23 strain and characterization of a new keratinase in the M4 metalloprotease family

Microbial keratinases have prominent potential in biotransformation of recalcitrant keratin substrates to value-added products which has made keratinases a research focus in the past decades. In this study, an efficient feather-degrading bacterium was isolated and identified as a novel species in Ectobacillus genus and designated as Ectobacillus sp. JY-23. The degradation characteristics analysis revealed that Ectobacillus sp. JY-23 could utilize chicken feathers (0.4% w/v) as the sole nutrient source and degraded 92.95% of feathers in 72 h. A significant increase in sulfite and free sulfydryl group content detected in the feather hydrolysate (culture supernatant) indicated efficient reduction of disulfide bonds, which inferred that the degradation mechanism of isolated strain was a synergetic action of sulfitolysis and proteolysis. Moreover, abundant amino acids were also detected, among which proline and glycine were the predominant free amino acids. Then, the keratinase of Ectobacillus sp. JY-23 was mined and Y1_15990 was identified as the keratinase encoding gene of Ectobacillus sp. JY-23 and designated as kerJY-23. Escherichia coli strain overexpressing kerJY-23 degraded chicken feathers in 48 h. Finally, bioinformatics prediction of KerJY-23 demonstrated that it belonged to the M4 metalloprotease family, which was a third keratinase member in this family. KerJY-23 showed low sequence identity to the other two keratinase members, indicating the novelty of KerJY-23. Overall, this study presents a novel feather-degrading bacterium and a new keratinase in the M4 metalloprotease family with remarkable potential in feather keratin valorization.

Insights into the keratin efficient degradation mechanism mediated by Bacillus sp. CN2 based on integrating functional degradomics

BACKGROUND

Keratin, the main component of chicken feather, is the third most abundant material after cellulose and chitin. Keratin can be converted into high-value compounds and is considered a potential high-quality protein supplement; However, its recalcitrance makes its breakdown a challenge, and the mechanisms of action of keratinolytic proteases-mediated keratinous substrates degradation are not yet fully elucidated. Bacillus sp. CN2, having many protease-coding genes, is a dominant species in keratin-rich materials environments. To explore the degradation patterns of feather keratin, in this study, we investigated the characteristics of feather degradation by strain CN2 based on the functional-degradomics technology.

RESULTS

Bacillus sp. CN2 showed strong feather keratin degradation activities, which could degrade native feathers efficiently resulting in 86.70% weight loss in 24 h, along with the production of 195.05 ± 6.65 U/mL keratinases at 48 h, and the release of 0.40 mg/mL soluble proteins at 60 h. The extracellular protease consortium had wide substrate specificity and exhibited excellent biodegradability toward soluble and insoluble proteins. Importantly, analysis of the extracellular proteome revealed the presence of a highly-efficient keratin degradation system. Firstly, T3 γ-glutamyltransferase provides a reductive force to break the dense disulfide bond structure of keratin. Then S8B serine endopeptidases first hydrolyze keratin to expose more cleavage sites. Finally, keratin is degraded into small peptides under the synergistic action of proteases such as M4, S8C, and S8A. Consistent with this, high-performance liquid chromatography (HPLC) and amino acid analysis showed that the feather keratin hydrolysate contained a large number of soluble peptides and essential amino acids.

CONCLUSIONS

The specific expression of γ-glutamyltransferase and co-secretion of endopeptidase and exopeptidase by the Bacillus sp. CN2 play an important role in feather keratin degradation. This insight increases our understanding of the keratinous substrate degradation and may inspire the design of the optimal enzyme cocktails for more efficient exploration of protein resources in industrial applications.

Chryseobacterium aquifrigidense keratinase liberated essential and nonessential amino acids from chicken feather degradation

Keratinous biomass valorization for value-added products presents a high prospect in ecological management and the advancement of the bio-economy. Consequently, soil samples from the poultry dumpsite were collected. The bacteria isolated on the basal salt medium were screened for keratinolytic activity. The potent chicken feathers degrading bacteria were identified through 16S rRNA gene sequencing and phylogenetic analysis. Fermentation process conditions were optimized, and the amino acid compositions of the feather hydrolysate were likewise quantified. Ten (10) proteolytic bacteria evaluated on skimmed milk agar showed intact chicken feather degradation ranging from 33% (WDS-03) to 88% (FPS-09). The extracellular keratinase activity ranged from 224.52 ± 42.46 U/mL (WDS-03) to 834.55 ± 66.86 U/mL (FPS-07). Based on 16S rRNA gene sequencing and phylogenetic analysis, the most potent keratinolytic isolates coded as FPS-07, FPS-09, FPS-01, and WDS-06 were identified as Chryseobacterium aquifrigidense FANN1, Chryseobacterium aquifrigidense FANN2, Stenotrophomonas maltophilia ANNb, and Bacillus sp. ANNa, respectively. C aquifrigidense FANN2 maximally produced keratinase (1460.90 ± 26.99 U/mL) at 72 h of incubation under optimal process conditions of pH (6), inoculum side (5%; v/v), temperature (30°C), and chicken feather (25 g/L). The feather hydrolysate showed a protein value of 67.54%, with a relative abundance of arginine (2.84%), serine (3.14%), aspartic acid (3.33%), glutamic acid (3.73%), and glycine (2.81%). C. aquifrigidense FANN2 yielded high keratinase titre and dismembered chicken feathers into amino acids-rich hydrolysate, highlighting its significance in the beneficiation of recalcitrant keratinous wastes into dietary proteins as potential livestock feed supplements.

Production and characterization of novel thermo- and organic solvent-stable keratinase and aminopeptidase from Pseudomonas aeruginosa 4-3 for effective poultry feather degradation

Feather biodegradation is an important premise for efficient resource development and utilization, in which keratinase plays an important role. However, there are few keratinases that combine the high activity, thermal stability, and organic solvent tolerance required for industrialization. This paper reported an efficient feather-degrading Pseudomonas aeruginosa 4-3 isolated from slaughterhouses. After 48 h of fermentation by P. aeruginosa 4-3 in a feather medium at 40 °C, pH 8.0, keratinase was efficiently produced (295.28 ± 5.42 U/mL) with complete feather degradation (95.3 ± 1.5%). Moreover, the keratinase from P. aeruginosa 4-3 showed high optimal temperature (55 °C), good thermal stability, wide pH tolerance, and excellent organic solvent resistance. In addition, P. aeruginosa 4-3-derived aminopeptidases also exhibit excellent thermal stability and organic solvent tolerance. Encouragingly, the reaction of crude keratinase and aminopeptidase with feathers for 8 h resulted in a 78% degradation rate of feathers. These properties make P. aeruginosa 4-3 keratinase and aminopeptidase ideal proteases for potential applications in keratin degradation, as well as provide ideas for the synergistic degradation of keratin by multiple enzymes.

Sustainable treatment of dye wastewater by recycling microalgal and diatom biogenic materials: Biorefinery perspectives

Discharge of untreated or partially treated toxic dyes containing wastewater from textile industries into water streams is hazardous for environment. The use of heavy metal(s) rich dyes, which are chemically active in azo and sulfur content(s) has been tremendously increasing in last two decades. Conventional physical and chemical treatment processes help to eliminate the dyes from textile wastewater but generates the secondary pollutants which create an additional environmental problem. Microalgae especially the diatoms are promising candidate for dye remediation from textile wastewater. Nanoporous diatoms frustules doped with nanocomposites increase the wastewater remediation efficiency due to their adsorption properties. On the other hand, microalgae with photosynthetic microbial fuel cell have shown significant results in being efficient, cost effective and suitable for large scale phycoremediation. This integrated system has also capability to enhance lipid and carotenoids biosynthesis in microalgae while simultaneously generating the bioelectricity. The present review highlights the textile industry wastewater treatment by live and dead diatoms as well as microalgae such as Chlorella, Scenedesmus, Desmodesmus sp. etc. This review engrosses applicability of diatoms and microalgae as an alternative way of conventional dye removal techniques with techno-economic aspects.

Feather-Degrading Bacillus cereus HD1: Genomic Analysis and Its Optimization for Keratinase Production and Feather Degradation

Keratinase is an important enzyme that is used to degrade feather wastes produced by poultry industries and slaughterhouses that accumulate rapidly over time. The search for keratinase-producing microorganisms is important to potentially substitute physicochemical treatments of feather waste. In this study, the genome of Bacillus cereus HD1 and its keratinolytic prowess was investigated. The whole-genome shotgun size is 5,668,864 bp consisting of 6083 genes, 69 tRNAs, and 10 rRNAs. The genomic analyses revealed 15 potential keratinase genes and other enzymes that might assist keratin degradation, such as disulfide reductase and cysteine dioxygenase. The optimal conditions for feather degradation and keratinase production by B. cereus HD1 such as incubation time, pH, temperature, yeast extract, and glycerol concentrations were determined to be 5 days, pH 8, 37 °C, 0.05% (w/v), and 0.1% (v/v), respectively. Under optimized conditions, B. cereus HD1 exhibited feather degradation of 65%, with bacterial growth and maximum keratinase activity of 1.3 × 10¹¹ CFU/mL and 41 U/mL, respectively, after 5 days of incubation in a feather basal medium. The findings obtained from this study may facilitate further research into utilizing B. cereus HD1 as a prominent keratinolytic enzymes production host and warrant potential biotechnological applications.

Keratinases as Versatile Enzymatic Tools for Sustainable Development

To reduce anthropological pressure on the environment, the implementation of novel technologies in present and future economies is needed for sustainable development. The food industry, with dairy and meat production in particular, has a significant environmental impact. Global poultry production is one of the fastest-growing meat producing sectors and is connected with the generation of burdensome streams of manure, offal and feather waste. In 2020, the EU alone produced around 3.2 million tonnes of poultry feather waste composed primarily of keratin, a protein biopolymer resistant to conventional proteolytic enzymes. If not managed properly, keratin waste can significantly affect ecosystems, contributing to environmental pollution, and pose a serious hazard to human and livestock health. In this article, the application of keratinolytic enzymes and microorganisms for promising novel keratin waste management methods with generation of new value-added products, such as bioactive peptides, vitamins, prion decontamination agents and biomaterials were reviewed.

Physicochemical and molecular characterization of heavy metal-tolerant bacteria isolated from soil of mining sites in Nigeria

Background

Mining for precious metals is detrimental to the composition of soil structure and microbial diversity distribution and is a health risk to human communities around the affected communities. This study was aimed at determining the physical and chemical characteristics and diversity of bacteria in the soil of local mining sites for biosorption of heavy metals.

Results

Results of physical and chemical characteristics showed mean pH values and percentage organic carbon to range from 7.1 to 8.2 and 0.18 to 1.12% respectively with statistical significance between sampling sites (P ≤ 0.05). Similarly, cation exchange capacity, electrical conductivity, moisture, total nitrogen, and carbon/nitrogen ratio (C:N) in the soil ranged between 1.52 to 3.57 cmol/kg, 0.15 to 0.32 ds/m, 0.14 to 0.82%, 0.10 to 0.28%, and 1.7 to 4.8 respectively. The highest heavy metal concentration of 59.01 ppm was recorded in soils obtained from site 3. The enumeration of viable aerobic bacteria recorded the highest mean count of 4.5 × 10⁶ cfu/g observed at site 2 with statistical significance (P ≤ 0.05) between the sampled soils. Alcaligenes faecalis strain UBI, Aeromonas sp. strain UBI, Aeromonas sobria, and Leptothrix ginsengisoli that make up 11.2% of total identified bacteria were able to grow in higher amended concentrations of heavy metals. The evolutionary relationship showed the four heavy metal–tolerant bacteria identified belonged to the phylum Proteobacteria of class Betaproteobacteria in the order Burkholderiales. Heavy metal biosorption by the bacteria showed Alcaligenes faecalis strain UBI having the highest uptake capacity of 73.5% for Cu.

Conclusion

In conclusion, Alcaligenes faecalis strain UBI (MT107249) and Aeromonas sp. strain UBI (MT126242) identified in this study showed promising capability to withstand heavy metals and are good candidates in genetic modification for bioremediation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-021-00251-x.

Optimisation of Various Physicochemical Variables Affecting Molybdenum Bioremediation Using Antarctic Bacterium, Arthrobacter sp. Strain AQ5-05

The versatility of a rare metal, molybdenum (Mo) in many industrial applications is one of the reasons why Mo is currently one of the growing environmental pollutants worldwide. Traces of inorganic contaminants, including Mo, have been discovered in Antarctica and are compromising the ecosystem. Bioremediation utilising bacteria to transform pollutants into a less toxic form is one of the approaches for solving Mo pollution. Mo reduction is a process of transforming sodium molybdate with an oxidation state of 6+ to Mo-blue, an inert version of the compound. Although there are a few Mo-reducing microbes that have been identified worldwide, only two studies were reported on the microbial reduction of Mo in Antarctica. Therefore, this study was done to assess the ability of Antarctic bacterium, Arthrobacter sp. strain AQ5-05, in reducing Mo. Optimisation of Mo reduction in Mo-supplemented media was carried out using one-factor-at-a-time (OFAT) and response surface methodology (RSM) approaches. Through OFAT, Mo was reduced optimally with substrate concentration of sucrose, ammonium sulphate, and molybdate at 1 g/L, 0.2 g/L, and 10 mM, respectively. The pH and salinity of the media were the best at 7.0 and 0.5 g/L, respectively, while the optimal temperature was at 10 °C. Further optimisation using RSM showed greater Mo-blue production in comparison to OFAT. The strain was able to stand high concentration of Mo and low temperature conditions, thus showing its potential in reducing Mo in Antarctica by employing conditions optimised by RSM.

A Thermostable Aluminum-Tolerant Protease Produced by Feather-Degrading Bacillus thuringiensis Isolated from Tea Plantation

BACKGROUND

Proteases with keratinolytic activity are widely used in biotechnologies. The feather-degrading Bacillus thuringensis isolated from soil sample of a tea plantation produced high level of extracellular keratinase.

OBJECTIVE

This study aimed to analyze the properties by biochemical and enzymological methods to gain information for better utilization of the enzyme.

METHODS

The enzyme was purified with ion exchange and size exclusion chromatography. The substrate preference, optimal pH and temperature, and the effects of organic solvents and ions were checked. Circular dichroism was performed to compare the secondary structures of the native and apo-enzyme.

RESULTS

The enzyme worked best at 50°C, and it was an acidic serine protease with an optimal pH of 6.2. Ions Ca²⁺ and Mg²⁺ were essential for its activity. Organic solvents and other metal ions generally deactivated the enzyme in a concentration-dependent manner. However, Mn²⁺ and DMSO, which were frequently reported as inhibitors of protease, could activate the enzyme at low concentration (0.01 to 2 mmol/L of Mn²⁺; DMSO <2%, v/v). The enzyme exhibited high resistance to Al³⁺, which might be explained by the soil properties of its host's residence. Circular dichroism confirmed the contribution of ions to the structure and activity.

CONCLUSION

The enzyme was a thermostable aluminum-tolerant serine protease with unique biochemical properties.

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.

Bacillus sp. CSK2 produced thermostable alkaline keratinase using agro-wastes: keratinolytic enzyme characterization

BACKGROUND

Chicken feathers are the most abundant agro-wastes emanating from the poultry processing farms and present major concerns to environmentalists. Bioutilization of intractable feather wastes for the production of critical proteolytic enzymes is highly attractive from both ecological and biotechnological perspectives. Consequently, physicochemical conditions influencing keratinase production by Bacillus sp. CSK2 on chicken feathers formulation was optimized, and the keratinase was characterized.

RESULTS

The highest enzyme activity of 1539.09 ± 68.14 U/mL was obtained after 48 h of incubation with optimized conditions consisting of chicken feathers (7.5 g/L), maltose (2.0 g/L), initial fermentation pH (5.0), incubation temperature (30 °C), and agitation speed (200 rpm). The keratinase showed optimal catalytic efficiency at pH 8.0 and a temperature range of 60 °C - 80 °C. The keratinase thermostability was remarkable with a half-life of above 120 min at 70 °C. Keratinase catalytic efficiency was halted by ethylenediaminetetraacetic acid and 1,10-phenanthroline. However, keratinase activity was enhanced by 2-mercaptoethanol, dimethyl sulfoxide, tween-80, but was strongly inhibited by Al³⁺ and Fe³⁺. Upon treatment with laundry detergents, the following keratinase residual activities were achieved: 85.19 ± 1.33% (Sunlight), 90.33 ± 5.95% (Surf), 80.16 ± 2.99% (Omo), 99.49 ± 3.11% (Ariel), and 87.19 ± 0.26% (Maq).

CONCLUSION

The remarkable stability of the keratinase with an admixture of organic solvents or laundry detergents portends the industrial and biotechnological significance of the biocatalyst.

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 and Molecular Characterization of a Thermostable Alkaline Metallo-Keratinase from Bacillus sp. Nnolim-K1

Keratinases are considerably gaining momentum in green technology because of their endowed robustness and multifaceted application potentials, such as keratinous agro-wastes valorization. Therefore, the production of novel keratinases from relatively nonpathogenic bacteria grown in agro-wastes formulated medium is cost-effective, and also imperative for the sustainability of thriving bioeconomy. In this study, we optimized keratinase production by Bacillus sp. Nnolim-K1 grown in chicken feather formulated medium. The produced keratinase (KerBNK1) was biochemically characterized and also, the keratinase-encoding gene (kerBNK1) was amplified and sequenced. The optimal physicochemical conditions for extracellular keratinase production determined were 0.8% (w/v) xylose, 1.0% (w/v) feather, and 3.0% (v/v) inoculum size, pH 5.0, temperature (25 °C) and agitation speed (150 rpm). The maximum keratinase activity of 1943.43 ± 0.0 U/mL was achieved after 120 h of fermentation. KerBNK1 was optimally active at pH and temperature of 8.0 and 60 °C, respectively; with remarkable pH and thermal stability. KerBNK1 activity was inhibited by ethylenediamine tetra-acetic acid and 1,10-phenanthroline, suggesting a metallo-keratinase. The amplified kerBNK1 showed a band size of 1104 bp and the nucleotide sequence was submitted to the GenBank with accession number MT268133. Bacillus sp. Nnolim-K1 and the keratinase displayed potentials that demand industrial and biotechnological exploitations.

Response Surface Methodology Optimization and Kinetics of Diesel Degradation by a Cold-Adapted Antarctic Bacterium, Arthrobacter sp. Strain AQ5-05

Petroleum hydrocarbons, notably diesel oil, are the main energy source for running amenities in the Antarctic region and are the major cause of pollution in this area. Diesel oil spills are one of the major challenges facing management of the Antarctic environment. Bioremediation using bacteria can be an effective and eco-friendly approach for their remediation. However, since the introduction of non-native organisms, including microorganisms, into the Antarctic or between the distinct biogeographical regions within the continent is not permitted under the Antarctic Treaty, it is crucial to discover native oil-degrading, psychrotolerant microorganisms that can be used in diesel bioremediation. The primary aim of the current study is to optimize the conditions for growth and diesel degradation activity of an Antarctic local bacterium, Arthrobacter sp. strain AQ5-05, using the Plackett-Burman approach and response surface method (RSM) via a central composite design (CCD) approach. Based on this approach, temperature, pH, and salinity were calculated to be optimum at 16.30 °C, pH 7.67 and 1.12% (w/v), respectively. A second order polynomial regression model very accurately represented the experimental figures’ interpretation. These optimized environmental conditions increased diesel degradation from 34.5% (at 10 °C, pH 7.00 and 1.00% (w/v) salinity) to 56.4%. Further investigation of the kinetics of diesel reduction by strain AQ5-05 revealed that the Teissier model had the lowest RMSE and AICC values. The calculated values for the Teissier constants of maximal growth rate, half-saturation rate constant for the maximal growth, and half inhibition constants (μmax, Ks, and Ki), were 0.999 h−1, 1.971% (v/v) and 1.764% (v/v), respectively. The data obtained therefore confirmed the potential application of this cold-tolerant strain in the bioremediation of diesel-contaminated Antarctic soils at low temperature.

Removal of Antibiotics from Aqueous Solutions by a Carbon Adsorbent Derived from Protein-Waste-Doped Biomass

Antibiotic pollution in water is an urgent environmental problem. A novel carbon adsorbent derived from powdery puffed waterfowl feather (PPWF)-doped Phragmites australis (PA) was proposed for enhancing the removal of antibiotics from water in this study. Amoxicillin (AMX) and cephalexin (CEX) were selected as typical antibiotics. PPWF-doped (FPAC) and -undoped (PAC) carbon adsorbents were developed to test the adsorption capacities and mechanisms of AMX and CEX. Characterization techniques such as N₂ adsorption/desorption, Fourier transform infrared, X-ray diffraction, scanning electron microscopy, elemental analysis, and Boehm titration were used to determine the properties of adsorbents. Results showed that more microporous structure and surface functional groups are exhibited in FPAC compared to PAC. The nitrogen-containing functional groups were introduced in FPAC. Adsorption capacities at different contact times, pH, and initial concentration were investigated by batch experiments. The AMX and CEX maximum adsorption capacities of FPAC are 25.2 and 30.1% higher than those of PAC, respectively. The kinetic data were well represented by the pseudo-second-order model for AMX and CEX adsorption. The equilibrium data agreed well with the Langmuir model for AMX adsorption and the Freundlich model for CEX adsorption. The adsorption mechanism of AMX and CEX was chemisorption, such as electrostatic attraction and covalent bonding.

Response Surface Methodology for the Optimization of Keratinase Production in Culture Medium Containing Feathers by Bacillus sp. UPM-AAG1

Keratinase is a type of proteolytic enzyme with broad application in industry. The main objective of this work is the optimization of keratinase production from Bacillus sp. strain UPM-AAG1 using Plackett-Burman (PB) and central composite design (CCD) for parameters, such as pH, temperature, feather concentration, and inoculum size. The optimum points for temperature, pH, and inoculum and feather concentrations were 31.66 °C, 6.87, 5.01 (w/v), and 4.53 (w/v), respectively, with an optimum keratinase activity of 60.55 U/mL. The keratinase activity was further numerically optimized for commercial application. The best numerical solution recommended a pH of 5.84, temperature of 25 °C, inoculums’ size of 5.0 (v/v), feather concentration of 4.97 (w/v). Optimization resulted an activity of 56.218 U/mL with the desirability value of 0.968. Amino acid analysis profile revealed the presence of essential and non-essential amino acids. These properties make Bacillus sp. UPM-AAG1 a potential bacterium to be used locally for the production of keratinase from feather waste.

Proteolytic bacteria isolated from agro-waste dumpsites produced keratinolytic enzymes

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Proteolytic bacteria were isolated from agro-waste dumpsites.

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The isolates degraded intact feathers and produced keratinases in basal media.

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Feather degradation generated high concentration of free thiol containing groups.

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The remarkable thiol concentrations suggest keratinous waste valorisation potential of these bacteria.

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The isolates were identified through 16S rDNA sequence as Bacillus spp. and Arthrobacter sp.

Microbial bioconversion of carbonoclastic materials is an efficient tool for the exploitation and valorization of underutilized agro-industrial wastes. The agro-industrial sector accumulates tones of keratinous wastes biomass which may be valorized into high value products. Consequently, the keratinolytic potentials of some bacteria isolated from terrestrial milieu was evaluated. Soil samples were collected from dumpsites, keratinase producing bacteria were isolated. Bacterial species were identified through 16S rRNA gene sequences. The keratinase activity was assessed in relation to thiol formation, percentage feather degradation and quantitation of keratinase produced. Keratinolytic bacteria were identified as Bacillus spp. (accession numbers: MG214989 – MG214992, MG214997, MG214998, MG215000, MG215002–MG215005) and Arthrobacter sp. (accession numbers; MG215001). The degree of chicken feather degradation ranged from 61.5 ± 0.71 % to 85.0 ± 1.41 %. Similarly, the activity of keratinase, total protein and thiol group ranged from 198.18 ± 15.43–731.83 ± 14.14 U/mL; 0.09 ± 0.01–0.87 ± 0.05 mg/mL; and 0.69 ± 0.12–2.89 ± 0.11 mM respectively. Notably, Bacillus sp. Nnolim-K1 displayed the best keratinolytic potential with extracellular keratinase activity and feather degradation of 731.83 ± 14.14 U/mL and 85.0 ± 1.41 % respectively, and that is an indication of a potential relevance biotechnologically.

Citrobacter diversus-derived keratinases and their potential application as detergent-compatible cloth-cleaning agents

Currently, poultry farming is one of the sectors that have a significant impact on the global economy. In recent years, there has been an increase in the production of broilers, inflicting this segment of the industry to generate tons of keratin due to huge disposal of chicken feathers. This points to the need to degrade these chicken feathers, as they have emerged as a major threat to the environment. Thus, in this study we aimed to identify keratinases that are produced by the bacterium Citrobacter diversus and further investigate the biochemical characteristics of these keratin-degrading enzymes. In a submerged medium, the bacterium was capable of degrading chicken feathers almost completely after 36 h of fermentation. We found a maximum caseinolytic activity at pH 9-10.5 and 50-55 °C, and keratinolytic activity at pH 8.5-9.5 and 50 °C. Thus, given its stability at higher temperatures, upon incubation of this enzyme extract for 1 h at 50 °C, it showed approximately 50% of the keratinolytic and 100% of the caseinolytic activity. Further, under pH stability for 48 h at 4 °C, the enzyme extract maintained greater residual activity in the pH range 6-8. Caseinolytic activity was inhibited by EDTA and PMSF, whereas the keratinolytic activity was inhibited only by EDTA. Additionally, due to its alkaline activity and detergent compatibility, this enzyme extract could improve washing performance when added to a commercial detergent formulation. Using application tests, we could demonstrate a potential use of this bacterial enzyme extract as an additive in detergents to remove egg stains from cloth.

Efficient Keratinolysis of Poultry Feather Waste by the Halotolerant Keratinase from Salicola Marasensis

Sustainable development in the bio-treatment of large-scale biomass bulks requires high performance enzymes adapted to extreme conditions. An extracellular keratinolytic extract was obtained from the culture broth of a halotolerant strain of Salicola marasensis. Keratin hydrolyzing activity of the concentrated enzyme extract was observed on a 100 mg of pretreated feather waste. The concentrated enzyme was able to hydrolyze the poultry feathers by 25% after 12 h incubation. The bio-waste material was optimally hydrolyzed at pH 9 and temperature of 40 °C. Among reductants, 1,4-dithiothreitol, L-cysteine, 2-mercaptoethanol, glutathione, and sodium sulfate showed the most remarkable effect on the bio-waste keratinolysis, while the tested surfactants and urea had no significant effect on the keratinolytic activity. Hexane and hexadecane indicated strong effect on keratinase activity and bio-treatment in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) as a hydrophobic ionic liquid resulted in a maximal of 80% extraction yield of soluble proteins from feathers. Considering the stability of the extracellular keratinolytic content in [BMIM][PF₆], the observed keratinase activity was noteworthy suggesting that the secreted enzyme may contribute to the bioconversion of feather wastes.

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.

Selective biodegradation of recalcitrant black chicken feathers by a newly isolated thermotolerant bacterium Pseudochrobactrum sp. IY-BUK1 for enhanced production of keratinase and protein-rich hydrolysates

Black chicken feathers generated in large amount from poultry and slaughter houses are highly recalcitrant to microbial degradation due to their tough structural nature. A novel keratinolytic bacterium that possessed high affinity for black feather was isolated from chicken manure and identified as Pseudochrobactrum sp. IY-BUK1. Keratinase and feather soluble protein were effectively produced by the free living cells of the bacterium in media containing only black feathers and a mixture of equal amount of black-, brown- and white-coloured feathers. Complete degradation of 5 g/L of black feathers was completed in 3 days following optimisation of physico-chemical conditions. However, the bacterium selectively completed the degradation of black feather in a medium containing mixture of feathers in 144 h leaving behind approximately 33% and 45% of brown and white feathers in the medium respectively. Gellan gum-immobilised cells of strain IY-BUK1 enhanced the keratinase production by about 150% and were used repeatedly for ten cycles to degrade 5 g/L of black feather in a semi continuous fermentation of 18 h per cycle with enhanced and stable production of soluble protein. The study demonstrated the potential use of Pseudochrobactrum sp. IY-BUK1 not only in biodegradation of highly recalcitrant black feathers, but also in producing keratinase enzymes and valuable soluble proteins for possible industrial usage.

Effective biodegradation of chicken feather waste by co-cultivation of keratinase producing strains

BACKGROUND

Chicken feather, a byproduct of poultry-processing industries, are considered a potential high-quality protein supplement owing to their crude protein content of more than 85%. Nonetheless, chicken feathers have been classified as waste because of the lack of effective recycling methods. In our previous studies, Bacillus licheniformis BBE11-1 and Stenotrophomonas maltophilia BBE11-1 have been shown to have feather-degrading capabilities in the qualitative phase. To efficiently recycle chicken feather waste, in this study, we investigated the characteristics of feather degradation by B. licheniformis BBE11-1 and S. maltophilia BBE11-1. In addition, in an analysis of the respective advantages of the two degradation systems, cocultivation was found to improve the efficiency of chicken feather waste degradation.

RESULTS

B. licheniformis BBE11-1 and S. maltophilia BBE11-1 were used to degrade 50 g/L chicken feather waste in batches, and the degradation rates were 35.4% and 22.8% in 96 h, respectively. The degradation rate of the coculture system reached 55.2% because of higher keratinase and protease activities. Furthermore, cocultivation was conducted in a 3 L fermenter by integrating dissolved oxygen control and a two-stage temperature control strategy. Thus, the degradation rate was greatly increased to 81.8%, and the conversion rate was 70.0% in 48 h. The hydrolysates exhibited antioxidant activity and contained large quantities of amino acids (895.89 mg/L) and soluble peptides.

CONCLUSIONS

Cocultivation of B. licheniformis BBE11-1 and S. maltophilia BBE11-1 can efficiently degrade 50 g/L chicken feather waste and produce large amounts of amino acids and antioxidant substances at a conversion rate of 70.0%.

Effective production of keratinase by gellan gum-immobilised Alcaligenes sp. AQ05-001 using heavy metal-free and polluted feather wastes as substrates

The ability of gellan gum-immobilised cells of the heavy metal-tolerant bacterium Alcaligenes sp. AQ05-001 to utilise both heavy metal-free and heavy metal-polluted feathers (HMPFs) as substrates to produce keratinase enzyme was studied. Optimisation of the media pH, incubation temperature and immobilisation parameters (bead size, bead number, gellan gum concentration) was determined for the best possible production of keratinase using the one-factor-at-a-time technique. The results showed that the immobilised cells could tolerate a broader range of heavy metal concentrations and produced higher keratinase activity at a gellan gum concentration of 0.8% (w/v), a bead size of 3 mm, bead number of 250, pH of 8 and temperature of 30 °C. The entrapped bacterium was used repeatedly for ten cycles to produce keratinase using feathers polluted with 25 ppm of Co, Cu and Ag as substrates without the need for desorption. However, its inability to tolerate/utilise feathers polluted with Hg, Pb, and Zn above 5 ppm, and Ag and Cd above 10 ppm resulted in a considerable decrease in keratinase production. Furthermore, the immobilised cells could retain approximately 95% of their keratinase production capacity when 5 ppm of Co, Cu, and Ag, and 10 ppm of As and Cd were used to pollute feathers. When the feathers containing a mixture of Ag, Co, and Cu at 25 ppm each and Hg, Ni, Pb, and Zn at 5 ppm each were used as substrates, the immobilised cells maintained their operational stability and biological activity (keratinase production) at the end of 3rd and 4th cycles, respectively. The study indicates that HMPF can be effectively utilised as a substrate by the immobilised-cell system of Alcaligenes sp. AQ05-001 for the semi-continuous production of keratinase enzyme.

Enrichment and characterization of an environmental microbial consortium displaying efficient keratinolytic activity

Keratin refers to a group of insoluble and recalcitrant protein materials. Slaughterhouses produce large amount of keratinous byproducts, which are either disposed or poorly valorized through costly thermochemical processes for animal feed formulation. Learning from nature, keratinolytic microbial consortia stand as a cost-efficient and environmental friendly way to valorize this recalcitrant resource. Directed selection was applied to enrich soil-born microbial consortia, using sequential batch cultivations in keratin medium, while measuring enzymes activity and monitoring consortia compositions via 16S rRNA gene amplicon sequencing. A promising microbial consortium KMCG6, featuring mainly members of Bacteroidetes and Proteobacteria, was obtained. It possessed keratinolytic activity with <25% residual substrate remaining, which also displayed a high degradation reproducibility level after long-term cryopreservation. This work represents an advance in the field of α-keratin degradation with potential for practical applications.

Low-molecular weight keratins with anti-skin aging activity produced by anaerobic digestion of poultry feathers with Fervidobacterium islandicum AW-1

Bioactive peptides contribute to various cellular processes including improved skin physiology. Hence, bioactive keratins have attracted considerable attention as active cosmetic ingredients for skin health. Here, we obtained low molecular weight (LMW) keratins from native chicken feathers by anaerobic digestion with an extremely thermophilic bacterium Fervidobacterium islandicum AW-1, followed by stepwise fractionation through ultrafiltration. To assess the effects of the feather keratins on skin health, we performed in vitro and ex vivo assays to investigate their inhibitory effects on matrix metalloproteinases (MMPs). As results, LMW feather keratins marginally inhibited collagenase, elastase, and radical scavenging activities. On the other hand, LMW feather keratins significantly suppressed the expression of ultraviolet B (UVB)-induced MMP-1 and MMP-13 in human dermal fibroblasts. Furthermore, phospho-kinase antibody array revealed that LMW feather keratins suppressed UVB-induced phosphorylation of Akts, c-Jun N-terminal kinases 1, p38 beta, and RSK2, but not ERKs in human dermal fibroblast. Overall, these results suggest that LMW feather keratins are potential candidates as cosmeceutical peptides for anti-skin aging.

Optimisation of culture composition for glyphosate degradation by Burkholderia vietnamiensis strain AQ5-12

The herbicide glyphosate is often used to control weeds in agricultural lands. However, despite its ability to effectively kill weeds at low cost, health problems are still reported due to its toxicity level. The removal of glyphosate from the environment is usually done by microbiological process since chemical process of degradation is ineffective due to the presence of highly stable bonds. Therefore, finding glyphosate-degrading microorganisms in the soil of interest is crucial to remediate this glyphosate. Burkholderia vietnamiensis strain AQ5-12 was found to have glyphosate-degrading ability. Optimisation of biodegradation condition was carried out utilising one factor at a time (OFAT) and response surface methodology (RSM). Five parameters including carbon and nitrogen source, pH, temperature and glyphosate concentration were optimised. Based on OFAT result, glyphosate degradation was observed to be optimum at fructose concentration of 6, 0.5 g/L ammonia sulphate, pH 6.5, temperature of 32 °C and glyphosate concentration at 100 ppm. Meanwhile, RSM resulted in a better degradation with 92.32% of 100 ppm glyphosate compared to OFAT. The bacterium was seen to tolerate up to 500 ppm glyphosate while increasing concentration results in reduced degradation and bacterial growth rate.

Effective feather degradation and keratinase production by Bacillus pumilus GRK for its application as bio-detergent additive

An effecient feather-degrading bacterium was isolated from poultry dumping yard and identified as Bacillus pumilus GRK based on 16S rRNA sequencing. Complete feather degradation (98.3±1.52%) with high keratinase production (373±4 U/ml) was observed in 24h under optimized conditions (substrate 1% (w/w); inoculum size 4% (v/v); pH 10; 200rpm at 37°C) with feathers as sole carbon and nitrogen source in tap water. The fermented broth was enriched with amino acids like tryptophan (221.44µg/ml), isoleucine (15.0µg/ml), lysine (10.81µg/ml) and methionine (7.24µg/ml) suggesting its potential use as feed supplement. The keratinase produced was a detergent stable serine protease and its activity was further enhanced by Ca⁺² and Mg⁺². Bacillus pumilus GRK keratinase was successfully utilised as bioadditive in detergent formulations for removing the blood stains from cloth without affecting its fiber and texture.