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

Silva, Ronivaldo Rodrigues da

doi:10.1021/acs.jafc.8b03152

Cited by 41 publications

(33 citation statements)

References 5 publications

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“…With the consumption of meat products, tens of millions of tons of keratin waste are produced each year worldwide, of which feather waste accounts for approximately 8.5 million tons [1,2]. Keratin is highly prevalent in animal coverings, including feathers, hair, scales, and nails [3,4].…”

Section: Introductionmentioning

confidence: 99%

Biotransformation of keratin waste to amino acids and active peptides based on cell-free catalysis

Peng

Mao

Zhang

et al. 2020

Biotechnol Biofuels

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Background: Keratin is the primary constituent of the vertebrate epidermis and epidermal appendages, as well as the main waste product generated during poultry processing from feathers, hair, scales, nails, etc. Keratin is generally hard, stubborn and difficult to hydrolyze; however, it is also inexpensive and contains more than 85% protein. Currently, tens of millions of tons of keratin waste are produced each year worldwide; however, no effective methods for the recovery of keratin waste have been reported thus far, making such research urgent. Keratinase has been reported to be useful for keratin waste recovery; however, nearly all keratinases are unable to hydrolyze keratin after they are detached from living cell systems. This may be due to low keratinase activity and lack of synergistic factors. Results: Herein, the keratinase gene from Bacillus licheniformis BBE11-1 was successfully expressed in Bacillus subtilis WB600, allowing for improved activity of the recombinant keratinase KerZ1 to 45.14 KU/mL via promoter substitution and screening of the ribosome-binding sites. Further, real-time control of temperature, pH, dissolved oxygen, and feed strategy allowed the activity of KerZ1 to reach 426.60 KU/mL in a 15-L fermenter, accounting for a 3552-fold increase compared to the wild-type keratinase (120.1 U/mL). Most importantly, we proposed a method based on the synergistic action of keratinase KerZ1 and sodium sulfite, to hydrolyze feathers into amino acids. In specific, 100 g/L of feather waste can be successfully converted into 56.6% amino acids within 12 h, while supporting the production of dozens of bioactive peptides. Conclusions: The activity of recombinant keratinase can be greatly enhanced via transcription and translational regulation in Bacillus subtilis. The synergistic action of keratinase and sulfite can rapidly degrade feather waste and produce amino acids and polypeptides.

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Section: Introductionmentioning

confidence: 99%

Biotransformation of keratin waste to amino acids and active peptides based on cell-free catalysis

Peng

Mao

Zhang

et al. 2020

Biotechnol Biofuels

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“…Feathers are an important by-product in poultry industry as they account for 5–7% of the body weight of chicken. It is estimated that approximately several million tons of feathers could be generated annually from poultry industry globally (Verma et al, 2017; da Silva, 2018). Feathers are usually collected and stored at certain areas before further treatment.…”

Section: Introductionmentioning

confidence: 99%

Progress in Microbial Degradation of Feather Waste

2019

Front. Microbiol.

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Feathers are a major by-product of the poultry industry. They are mainly composed of keratins which have wide applications in different fields. Due to the increasing production of feathers from poultry industries, the untreated feathers could become pollutants because of their resistance to protease degradation. Feathers are rich in amino acids, which makes them a valuable source for fertilizer and animal feeds. Numerous bacteria and fungi exhibited capabilities to degrade chicken feathers by secreting enzymes such as keratinases, and accumulated evidence shows that feather-containing wastes can be converted into value-added products. This review summarizes recent progress in microbial degradation of feathers, structures of keratinases, feather application, and microorganisms that are able to secrete keratinase. In addition, the enzymes critical for keratin degradation and their mechanism of action are discussed. We also proposed the strategy that can be utilized for feather degradation. Based on the accumulated studies, microbial degradation of feathers has great potential to convert them into various products such as biofertilizer and animal feeds.

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“…The use of microbial enzymes for the degradation of keratinous residues, especially the chicken feather keratin, proves to be a valuable alternative to solve the problem of accumulation of this poultry by-product in the environment. Unlike acid hydrolysis, keratinases require milder conditions for hydrolysis with reduced impairment of the protein hydrolysate [7,26]. Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Industrially, keratin residues are principally derived from the meat industry, such as pig hooves, cattle, and especially chicken feathers. For this reason, keratinolytic enzymes have attracted biotechnological interest as an alternative for dealing with the disposal of chicken feathers [7].…”

Section: Introductionmentioning

confidence: 99%

“…Upon feather degradation, the keratin hydrolysates can be readily used as biofertilizers and animal feed supplements, and possess biological activity such as antioxidant and antimicrobial [26]. Additionally, keratinases also have potential industrial applications, such as additives in detergent formulations [7,27]. The biochemical action of these enzymes on various proteins and their stability at alkaline pH makes them an important component of formulations that can be readily used for removing protein stains from cloth.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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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.

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

Cited by 41 publications

References 5 publications

Biotransformation of keratin waste to amino acids and active peptides based on cell-free catalysis

Biotransformation of keratin waste to amino acids and active peptides based on cell-free catalysis

Progress in Microbial Degradation of Feather Waste

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

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