Keratinases as an Alternative Method Designed To Solve Keratin

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Keratinases as an Alternative Method Designed To Solve Keratin Disposal on the Environment: Its Relevance on Agricultural and Environmental Chemistry

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Ronivaldo Rodrigues da Silva* Instituto de Biociências, Letras e Ciências Exatas, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), São José do Rio Preto, São Paulo 14051130, Brazil basis of a new technology. The lack of a use for the keratinous material makes it disposable in nature, although difficult to decompose because it is a recalcitrant compound. Thus, its disposal leads to environmental problems.1,3 Keratin hydrolysates can be obtained by treatment of keratin-rich samples with alkali, acids, or enzymes.3 From among these treatment options, the advantage of sustainable hydrolysates obtained by enzymatic action is well-known; the hydrolysis process proceeds under milder reaction conditions and does not require the use of environmentally harmful reagents. With regard to the use of keratin hydrolysate as a protein source, the physicochemical treatments can cause a loss of essential amino acids (i.e., methionine, lysine, and tryptophane) and, consequently, decrease their nutritional potential.3 In the case of prion proteins, decontamination of surgical materials through proteolytic degradation is less likely to damage medical equipment. verpopulation has contributed to the increased demand Keratinases, a Versatile Catalyst for a Sustainable for food and, consequently, to generation of low-use Technology. The large number of cysteine residues in keratin byproducts in the industrial sector. Among these byproducts, confers a rigid molecular arrangement as a result of the the generation of chicken feathers by the poultry industry is covalent interactions in disulfide bonds.1 Hydrophobic highlighted. The deposition of this recalcitrant protein interactions and hydrogen bonds also contribute to the rigidity constitutes a huge environmental problem because of its of the molecular structure of keratin. This rigidity makes it difficult degradation. Thus, the enzymatic hydrolysis of these difficult for conventional proteolytic enzymes to degrade wastes has shown to be an important sustainable alternative for keratin. Keratin degradation is performed by peculiar this sector. proteolytic enzymes named “keratinases” or “keratinolytic In this regard, studies involving new technologies exploit 1 enzymes”. microbial biodiversity as the major natural source for enzyme By definition, keratinases are proteolytic enzymes (peptiproduction.1,3 In fact, for a long time, microorganisms have dases or proteases) capable of cleaving peptide bonds in been considered as an invaluable natural resource for use in 1 1 There are many potential applications of keratinases. keratin. sustainable technology. Microbial production of keratinases is As mentioned previously, a promising application of these the subject of discussion in the present work. enzymes related to environmental cleaning is the degradation We Need To Invest in Keratinases. In recent years, there of chicken feathers. In addition, the degradation of this residue has been a constant growth in broiler production, with values produces a hydrolyzed material that is a rich source of amino estimated to reach 91.3 million tons in 2018, especially in 1,3 acids. countries such as the United States, Brazil, China, and the As shown in Table 1, a broad range of potential applications European Union (http://www.wattagnet.com/articles/32417for keratinases has been described recently. These applications world-broiler-production-to-increase-1-percent-in-2018?v= include the use of keratinases in human hair treatments and preview). Feathers comprise about 8−10% of the weight of depilatory creams,1 as detergent additives for removing protein chickens and are composed of around 90% keratin. In this 2 stains, biopesticide production for mosquito control,4 scenario, a large amount of keratinous material (feathers) from potential application in animal feed and plant growth3 and poultry can be expected annually. Currently, the estimated peptide production,1 and the use of feather hydrolysate for global feather waste from broiler production is about 8.5 biogas production,5 among others. million tons. This reveals the importance of adding a commercial value to these keratinous residues. In view of the production of keratinous residues from Received: June 16, 2018 aviculture, the degradation of this raw material provides the

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© XXXX American Chemical Society

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DOI: 10.1021/acs.jafc.8b03152 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

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6 medicine: prion degradation

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agriculture: organic plant biostimulant biopesticide for mosquito control feather hydrolysate for biogas production

Keratinase from Bacillus licheniformis (K4519, SigmaAldrich) is an example of commercially available keratinase. It is a recombinant enzyme with a wide spectrum of application, in particular, for degradation of chicken feather (https://www.sigmaaldrich.com/catalog/product/sigma/ k4519?lang=pt®ion=BR). Another example of commercially available keratinase is Valkerase enzyme that has also demonstrated an effective action on chicken feather (BioResource International, https://briworldwide.com/products/ valkerase/). As a result of the particular catalytic properties of these enzymes, supported by their wide action spectrum and various applications, it would be fascinating to only highlight their ability to degrade keratin and add value to this recalcitrant material. However, the applications of keratinases extend to various fields (Table 1), especially in the treatment of samples contaminated with prions.6 It is, therefore, clearly necessary to reinforce the remarkable scientific relevance of keratinases as an alternative method designed to eliminate or reduce these impacts of keratin disposal; it is also necessary to discuss the biochemical diversity found in microorganisms, which have been shown to be an important source for the production of these enzymes. For a long time, microbiology has paved the way for the development and innovation in environmental technology. Looking to the Future. In this viewpoint, I have taken a critical look at the future of sustainable technology, which is oriented toward seeking new alternatives to replace conventional methods of organic matter transformations that use chemical agents and physical treatments harmful to the environment and human health. It is, therefore, necessary to evaluate enzymatic technologies that have offered advances in this endeavor. New information on keratinases is becoming available, and their new potential applications are constantly emerging. It is worth highlighting the valuable contribution of studies in biochemistry and microbiology as well as the brilliance of scientists who strive to improve our understanding of these enzymes, mainly for the use of keratinases as an alternative method on agricultural and environmental chemistry. In this regard, this viewpoint highlights the use of biomass derived from chicken farming. The conscious opinion presented in this paper aligns with the idea that a constant increase in chicken production would expectedly result in a large amount of keratinous waste for the next few years. This projection reintroduces the need to add value to this animal biomass and make it useful for application in several other industries. The future offers us the opportunity to improve our participation as advocates of sustainable technologies. Let this be a trend all over the world!

SmB, submerged bioprocess; SSB, solid-state bioprocess.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Ronivaldo Rodrigues da Silva: 0000-0002-6504-8406 Notes

The author declares no competing financial interest.

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Bacillus licheniformis N22

SmB (at initial pH 7 and 37 °C) SmB (32 h at initial pH 8.5 and 50 °C)

not exhibited

bacterial keratinases Paenibacillus woosongensis TKB2 bacterial keratinases Bacillus thuringiensis Bacillus sp.

crude enzymatic extract

purified enzyme: exclusive action of proteolytic enzymes production of hydrolysate keratin via aerobic cultivation of Bacillus sp. keratinase and biosurfactant from Pseudomonas aeruginosa

keratinase production from bacterial species; these enzymes can be useful in peptide synthesis with promissor biostimulant function on plant growth keratinase is a crucial role for growing B. thuringiensis in chicken feathers as a substitute for conventional culture media; the enzyme has been suggested as an important tool to produce bacterial culture for biopesticide application keratin hydrolysate was obtained by SmB under cultivation for 2, 4, 6, or 8 days and used for biogas production via anaerobic fermentation; the biological pretreatment of keratin waste has been shown to be an efficient process to provide substrate for anaerobic fermentation bacterial keratinase in combination with biosurfactant was able to efficiently degrade prion protein at 65 °C; after keratinolytic action, the authors were unable to detect PrPSc by western blot analysis

2 detergent additive

SmB (48 h at initial pH 8.5 and 30 °C) SmB and SSB crude enzymatic extract

production and application of bacterial keratinase; the enzymes are efficient in the dehairing processes in leather treatment SmB and SSB crude enzymatic extract

keratinase production and evaluation of washing performance in commercial detergent compatibility; the enzyme exhibited maximum activity at pH 9 and an excellent washing performance at 50 °C

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cosmetic: treatment of human hair, depilatory cream tannery applications

potential application report summary

SmB and SSB crude enzymatic extract bacterial keratinases

bioprocessa enzyme sample keratinase source

Table 1. Some Examples of Potential Applications for Keratinases

production and application in formulation of hair removal cream

reference

Journal of Agricultural and Food Chemistry

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DOI: 10.1021/acs.jafc.8b03152 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

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Journal of Agricultural and Food Chemistry

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REFERENCES

(1) da Silva, R. R. Bacterial and fungal proteolytic enzymes, production, catalysis and potential applications. Appl. Biochem. Biotechnol. 2017, 183, 1−19. (2) Paul, T.; Das, A.; Mandal, A.; Halder, S. K.; Jana, A.; Maity, C.; DasMohapatra, P. K.; Pati, B. R.; Mondal, K. C. An efficient cloth cleaning properties of a crude keratinase combined with detergent: Towards industrial viewpoint. J. Cleaner Prod. 2014, 66, 672−684. (3) da Silva, R. R. Enzymatic synthesis of protein hydrolysates from animal proteins: exploring microbial peptidases. Front. Microbiol. 2018, 9, 735. (4) Poopath, S.; Thirugnanasambantham, K.; Mani, C.; Lakshmi, P. V.; Ragul, K. Purification and characterization of keratinase from feather degrading bacterium useful for mosquito controlA new report. Trop. Biomed. 2014, 31, 97−109. (5) Patinvoh, R. J.; Feuk-Lagerstedt, E.; Lundin, M.; Sárvári Horváth, I.; Taherzadeh, M. J. Biological pretreatment of chicken feather and biogas production from total broth. Appl. Biochem. Biotechnol. 2016, 180, 1401−1415. (6) Okoroma, E. A.; Purchase, D.; Garelick, H.; Morris, R.; Neale, M. H.; Windl, O.; Abiola, O. O. Enzymatic formulation capable of degrading scrapie prion under mild digestion conditions. PLoS One 2013, 8, e68099.

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DOI: 10.1021/acs.jafc.8b03152 J. Agric. Food Chem. XXXX, XXX, XXX−XXX