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

Co-culture of Acinetobacter sp. and Scedosporium sp. immobilized beads for optimized biosurfactant production and degradation of crude oil

The widespread exploration and exploitation of crude oil has increased the prevalence of petroleum hydrocarbon pollution in the marine and coastal environment. Bioremediation of petroleum hydrocarbons using cell immobilization techniques is gaining increasing attention. In this study, the crude oil degradation performance of bacterial and fungal co-culture was optimized by entrapping both cells in sodium-alginate and polyvinyl alcohol composite beads. Results indicate that fungal cells remained active after entrapment and throughout the experiment, while bacterial cells were non-viable at the end of the experimental period in treatments with the bacterial-fungal ratio of 1:2. A remarkable decrease in surface tension from 72 mN/m to 36.51 mN/m was achieved in treatments with the bacterial-fungal ratio of 3:1. This resulted in a significant (P < 0.05) total petroleum hydrocarbon (TPH) removal rate of 89.4%, and the highest degradation of n-alkanes fractions (from 2129.01 mg/L to 118.53 mg/L), compared to the other treatments. Whereas PAHs removal was highest in treatments with the most fungal abundance (from 980.96 μg/L to 177.3 μg/L). Furthermore, enzymes analysis test revealed that catalase had the most effect on microbial degradation of the target substrate, while protease had no significant impact on the degradation process. High expression of almA and PAH-RHDa genes was achieved in the co-culture treatments, which correlated significantly (P < 0.05) with n-alkanes and PAHs removal, respectively. These results indicate that the application of immobilized bacterial and fungal cells in defined co-culture systems is an effective strategy for enhanced biodegradation of petroleum hydrocarbons in aqueous systems.

Microbial proteases: ubiquitous enzymes with innumerable uses

Proteases are ubiquitous enzymes, having significant physiological roles in both synthesis and degradation. The use of microbial proteases in food fermentation is an age-old process, which is today being successfully employed in other industries with the advent of ‘omics’ era and innovations in genetic and protein engineering approaches. Proteases have found application in industries besides food, like leather, textiles, detergent, waste management, agriculture, animal husbandry, cosmetics, and pharmaceutics. With the rising demands and applications, researchers are exploring various approaches to discover, redesign, or artificially synthesize enzymes with better applicability in the industrial processes. These enzymes offer a sustainable and environmentally safer option, besides possessing economic and commercial value. Various bacterial and fungal proteases are already holding a commercially pivotal role in the industry. The current review summarizes the characteristics and types of proteases, microbial source, their current and prospective applications in various industries, and future challenges. Promoting these biocatalysts will prove significant in betterment of the modern world.

Use and treatment of chicken feathers as a natural adsorbent for the removal of copper in aqueous solution

PURPOSE

Copper is a heavy metal that causes considerable deterioration to human health and ecosystems, so their elimination in water bodies is of great interest. Present investigation shows the efficiency of chicken feather as a natural adsorbent and its subsequent degradation in order to have an integral treatment and avoid the unconscious disposition.

METHODS

Optimal conditions of adsorption process were determined using the Response Surface Methodology (RSM)-Box-Behnken design (BBD) with three variables (pH, temperature and adsorbent dose). After that, the optimal conditions were used to analize the adsorption isotherms by Langmuir, Freundlich and Temkin models; also thermodynamics parameters Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were obtained. Finally, the biodegradation of the residue denominated "adsorbent-adsorbate" complex was evaluated through monitoring the soluble protein production, keratinolytic activity, ninhydrin positive products, sulfhydryl groups, and gravimetrically analysis.

RESULTS

The optimum conditions for the adsorption were 30°C and pH 3, the Langmuir model was better described the adsorption process at 30°C, while at 40°C was Temkin model. The chicken feather turned out a natural adsorbent competitive with respect to others used in the removal of copper in liquid systems; obtaining qmax of 7.84 and 11.48 mg/g at 30 and 40°C, respectively; it was also a favorable and spontaneous process. Finally the adsorbent used was degraded by a keratinolytic consortium.

CONCLUSIONS

In this study, chicken feather was used as a low cost adsorbent for copper efficiently and with the feasibility that the adsorbent can be biodegraded and release the metal.

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

OBJECTIVES

The bioaccumulation of keratinous wastes from poultry and dairy industries poses a danger of instability to the biosphere due to resistance to common proteolysis and as such, microbial- and enzyme-mediated biodegradation are discussed.

RESULTS

In submerged fermentation medium, Proteus vulgaris EMB-14 utilized and efficiently degraded feather, fur and scales by secreting exogenous keratinase. The keratinase was purified 14-fold as a monomeric 49 kDa by DEAE-Sephadex A-50 anion exchange and Sephadex G-100 size-exclusion chromatography. It exhibited optimum activity at pH 9.0 and 60 °C and was alkaline thermostable (pH 7.0-11.0), retaining 87% of initial activity after 1 h pre-incubation at 60 °C. The K_m and V_max of the keratinase with keratin azure were respectively 0.283 mg/mL and 0.241 U/mL/min. Activity of P. vulgaris keratinase was stimulated by Ca²⁺, Mg²⁺, Zn²⁺, Na⁺ and maintained in the presence of some denaturing agents, except β-mercaptoethanol while Cu²⁺ and Pb²⁺ showed competitive and non-competitive inhibition with K_i 6.5 mM and 17.5 mM, respectively.

CONCLUSION

This purified P. vulgaris keratinase could be surveyed for the biotechnological transformation of bioorganic keratinous wastes into valuable products such as soluble peptides, cosmetics and biodegradable thermoplastics.

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.

Challenges and Opportunities in Identifying and Characterising Keratinases for Value-Added Peptide Production

Keratins are important structural proteins produced by mammals, birds and reptiles. Keratins usually act as a protective barrier or a mechanical support. Millions of tonnes of keratin wastes and low value co-products are generated every year in the poultry, meat processing, leather and wool industries. Keratinases are proteases able to breakdown keratin providing a unique opportunity of hydrolysing keratin materials like mammalian hair, wool and feathers under mild conditions. These mild conditions ameliorate the problem of unwanted amino acid modification that usually occurs with thermochemical alternatives. Keratinase hydrolysis addresses the waste problem by producing valuable peptide mixes. Identifying keratinases is an inherent problem associated with the search for new enzymes due to the challenge of predicting protease substrate specificity. Here, we present a comprehensive review of twenty sequenced peptidases with keratinolytic activity from the serine protease and metalloprotease families. The review compares their biochemical activities and highlights the difficulties associated with the interpretation of these data. Potential applications of keratinases and keratin hydrolysates generated with these enzymes are also discussed. The review concludes with a critical discussion of the need for standardized assays and increased number of sequenced keratinases, which would allow a meaningful comparison of the biochemical traits, phylogeny and keratinase sequences. This deeper understanding would facilitate the search of the vast peptidase family sequence space for novel keratinases with industrial potential.

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.