INTRODUCTION
Chicken feathers constitute four to six per cent of the weight of the chicken and are regarded as a worthless byproduct of the poultry business. Though in minuscule amounts, feathers are used in decorations and packaging. The majority of the feathers are a major source of pollution and are obtained from slaughterhouses.
Proteins
Proteins are essential to human life. They rank among the most crucial biological molecules of bodily tissue. Amino acid components are bonded together by peptide bonds, comprising proteins (Gonzalez and Vaillard,2013). The amino connections created between carboxylic acid and amino acid molecules are known as peptide linkages (Sheridan and Krishnaiah,2019).
Proteins are long macromolecular chains joined by polypeptide bonds(Frisch et al,2020). Examples of fibrous materials that have been extensively studied are proteins, such as keratin, collagen, elastin, and silk. Since the protein material qualities are comparable to each other, they can be manufactured similarly (Jao et al,2017).
It is one of the most important sources of animal protein that is primarily consumed worldwide. Their consumption has led to the production of a significant amount of feather waste byproducts from poultry slaughterhouses, as feathers account for over 7% of body weight.
It is believed that the expected number of people generated each year globally is around 15 billion tons, with South Africa contributing approximately 258 million tons. Meat is one of the most important sources of animal protein that is primarily consumed worldwide (Tesfaye et al, 2017).
CHICKEN FEATHERS
The weight of feathers in a is roughly four to six per cent and is generally considered an insignificant byproduct in the poultry industry. Though only a small portion of feathers are utilized in decorations and packaging, the majority are a significant source of pollution and originate from slaughterhouses.
Nearly five billion tons of waste are generated annually by poultry production, according to (Vineis et al,2019). The majority of them are occasionally disposed of by burning or dumping in landfills, however, these processes are not ecologically friendly.
One of the main causes of environmental contamination is the handling and storage of feathers in enormous quantities. One of the main causes of air pollution is the pollutants produced during incineration (Nogja and Jadhav,2019).
TYPES OF CHICKEN FEATHERS
Feathers are currently used to make insignificant volumes of animal feed. Even so, most of them, aside from some that are added to subpar animal feed produced by both small and large enterprises in numerous nations, wind up in landfills, posing a threat to the environment (Chinta et al, 2013).
However, they are renewable resources that are abundant in keratin protein, which is a fibrous, stiff kind of protein also present in nails, hair, skin, and hooves (Sharma and Gupta, 2016). Waste feathers cannot be disposed of in an environmentally sustainable way, hence studies into their beneficiation are required to create low-cost, renewable, biodegradable, and readily available green materials (Tesfaye et al, 2018).
Term: Keratin
The term “keratin” is used to refer to all the proteins eradicated from skin modifications such as hooves, claws, and horns. Later research revealed that this so-called “keratin” is a mixture of various proteins, including enzymes, and keratins as well as proteins connected to keratin filaments.
Proteins that form filaments and are removed from the cornified layer of the epidermis are referred to as “keratins” or “cytokeratins,” whereas proteins that form filaments and are extracted from the living layers of the epidermis are referred to as “keratins” and have features that are unique to them.
The term “keratin” now encompasses any structural protein that forms an intermediate filament. Keratin is the most ubiquitous structural protein found in animal horns, claws, nails, hair, and feathers. Next to collagen is the most significant biopolymer found in mammals. The fibrous keratin proteins contain long polypeptide chains and cross-link fibres. (Chilakamaryetal,2021).
Vital protein
Keratin is a vital and structural protein that is plentiful and essential. It is present in many commercial waste products, including skin remnants, animal hair, horns, hooves, and feathers, as well as slaughter byproducts (Idris et al,2012,- Kalia,2019., Reddy (2017) Teresa and Justyna,2011).
Primary, secondary, and tertiary structures can be found in intricate hierarchical structures. Additionally, it is widely distributed in two forms: α- and β-keratins, with the former found in mammals and the latter in birds and reptiles (Barone et al,2005, Kamarudin,2017).
This work focuses on the extraction of keratin, which has drawn a lot of interest because of its biocompatibility, biological function, and biodegradability in a variety of applications, including tissue engineering, regenerative medicine, and cosmetics (Agarwal,., et al,2019).
KERATIN ABUNDANT STRUCTURAL PROTEIN
Alongside collagen, keratin is the most prevalent structural protein in epithelial cells and the most significant biopolymer in animals. Its structural organization and crystallinity are influenced by its use in nature. Each of these is related to its purpose, such as controlling moisture and thermal insulation (found in wool) or more structural functions (found in chicken feathers) feathers (Shah et al,2019). Keratin can self-assemble and is therefore useful for protection. It can be used directly as the primary component of armour or, discreetly, in damage-tolerant structures to create a barrier that protects the entire animal or specific vital bodily regions. ( Islam,2021).
Properties of Keratin
Keratin is a hard, fibrous protein that is the third most common polymer in the environment, after cellulose and chitin. It is the main component of the hair, feathers, nails, wool, hooves, and horns of mammals, reptiles, and birds. It is non-toxic and exhibits special qualities related to biodegradability and biocompatibility.
Furthermore, it can be created and altered into a variety of forms, including gels, films, beads, nanoparticles, and microparticles (Khosa, and. Ullah,2013). As such, it serves as a significant source of sustainable and renewable raw materials for a wide range of applications(Wang, et al,2016).
The business produces millions of tons of feathers as a byproduct each year for use throughout the world. The output of poultry meat is rising in tandem with an increase in the amount of waste feathers. This results in pollution, a challenging disposal situation for the environment, and potential health risks for peoPollution can cause human health issues (Endo et al 2008, Poole and Church,2017).
The production of inexpensive, value-added products made from scrap and renewable resources is becoming more and more popular these days. Different amino acids can be polymerized to create proteins. (Gupta, etal2012).
DO CHICKEN FEATHERS GROW BACK
Naturally occurring in the environment, feather waste contains around 85% crude protein, 70% amino acids, vitamins, high-value elements, and growth hormones. Feather waste is biodegradable. May be utilized as feed (Odetallah,etal2003), fertilizer (Guzzo, et al,2006), or biofilm (Abdel-Fattah,2013). due to the important materials they contain. Feathers are not adequately recycled at this time.
(Peng, et al,2019). Hence, it is imperative to devise a technique that can convert discarded feathers into novel materials that have the potential to be economical and ecologically sustainable.
These days, a greater number of environmentally friendly techniques utilizing renewable resources are required. One important source of renewable materials is proteins. Feathers include keratin protein. Frs from are a readily accessible, unique, and cost-effective byproduct of the poultry business. (Shavandi.,etal.,2017).
Quality of Chicken Feathers
Excellent qualities include their high keratinous protein content and hydrophobic structure, which enhance the end product’s resistance to water. Furthermore, the feather protein’s hydrolysis is aided by its fibrin units and innate anti-mildew properties.
are a popular option for many applications requiring resilient tensile strength and flexibility because of these unique qualities as well as their wide availability, sustainability, and affordability(Nuutinen,2017).
In order to produce films, fibres, hydrogels, binders, and micro- and nanoparticles for industrial, medicinal, textile, and cosmetic applications, keratin protein can therefore be obtained and used as a natural raw material (Khosa and Ullah, 2013).
Sources of keratin
A substantial quantity of keratin may be found in, which is generated annually as a byproduct of the poultry industry. This means serving as a rich source of keratin (Ji et al 2014 Olonilebi, 2017). Glycine, alanine, serine, and tyrosine constitute the repeating pattern that makes up its main structure. A prolonged polypeptide chain is formed by repeatedly executing this sequence.
Keratin’s distinctive characteristics, such as its strength, elasticity, and resilience, are a result of its particular amino acid composition.
Keratin’s secondary structure is illustrated by alpha-helices, which arise from the polypeptide chain bending around itself. After that, the alpha-helices coalesce to create coiled-coil structures, which combine to form protofilaments.
Intermediate filaments are the structural elements of keratin fibers, fibres when the proto filaments bundle together. The intermediate filaments are folded and packed into a three-dimensional structure to form the tertiary structure of keratin. Keratin’s special qualities come from its three-dimensional structure, which also enables it to create sturdy and tensile fibers ( Guzman,2011).
CHARACTERISTICS AND WOOL
Alpha and beta keratin filament matrix structures are the two types that characterize wool and feathers at the nanoscale. Alpha keratin proteins, in particular, are structured in spiral coils. The filament forms a right-handed coil as it stretches; two chains made of disulphide cross-link a left-handed coil known as the dimer, which is 45 nm long.
After that, dimers group end to end and stagger side by side via disulphide bonds to form a protofilament, which has a diameter of about 2 nm. Two proto-filaments are then laterally associated to form a proto-fibril, and four proto-fibrils come together to form a 7 nm circular or helical intermediate filament (McKittrick, 2012).
Two things collaborate to secure the structure of the pleated sheet: first, the peptide bond pushes a beta-sheet into pleating, and second, the hydrogen bonds between the beta strands assist in creating a sheet. The folded sheet bends into a left-handed helix to generate the beta keratin filament. A 4 nm-diameter pleat is formed when two pleated sheets overlap and wind in opposite directions (Wang, et al, 2016).
Keratin’s peptide chain components are cross-linked by cysteine bonds that confer high stability and xenobiotic nature. Literature suggests that keratin protein is not soluble in water, but that it can be improved by heating it and adding a reducing agent when the pH is mildly acidic (Donato and Mija, 2020).
Despite the exception of some –NH2 and other groups protonating after the reduction, the crosslinks between the disulphide will be dissolved into free thiol (-SH), making their surface positive before dissolution occurs (Khosa and Ullah, 2013).
Keratin extraction
One of keratin’s key characteristics is its ability to flex in various directions without rupturing. It also gives tissues a strong, fibrous matrix (Yamauchi et al,2002). Keratin can be dissolved and extracted using a variety of techniques.
These techniques include steam explosion, oxidation, supercritical water extraction, reduction hydrolysis, alkaline hydrolysis, sulphitolysis, and extraction using ionic liquids, microbiological and enzymatic techniques have also been employed for keratin extraction in addition to microwave-assisted extraction.
(Shavandi et al, 2017). Numerous investigations have shown that by implementing these techniques, it is possible to produce keratin protein by breaking the disulphide bonds present in the cysteine unit(Kamarudin et al, 2017).
For instance, a good yield of keratin protein from several animal sources was obtained by using sodium sulfide,sulphideapto3ethanol, and sodium.
Techniques including alkali extraction, reduction, oxidation, ionic liquids (ILs), and deep eutectic solvent (DES) are frequently employed to remove keratin from keratin-rich materials. To hydrolyze and neutralize with acid, the alkaline extraction process needs a lot of alkaline substances. The hydrolysis process causes an interruption in the keratin structure.
As a result, the alkali treatment greatly affects the amount of amino acids in the keratin that is produced, and the yield of keratin is very poor as a result of the significant amino acid loss. acids (Tsuda and Nomura, Anim (2014). There have been numerous reports on the use of thiols (such as mercaptoethanol) as a reducing agent for keratin extraction.
DISADVANTAGES OF VARIOUS CHEMICALS FOR KERATIN EXTRACTION
Mercaptoethanol (MEC) is used for extraction, which preserves the keratin chain structure, although it has drawbacks such as high cost and potential toxicity (Schrooyen, et al.,2001). The oxidation method offers a reasonably easy extraction process when compared to other methods, but it has the drawback that perchloric or peracetic acid will oxidize partial cystine to cysteic acid (Shavandi, et al,2017).
Organic and inorganic nations combine to form ILs, a novel class of environmentally friendly solvents. Due to their ability to retain (or adjust) the original polymer’s qualities as well as their recyclability, they have been utilized as a gentle alternative to chemical treatments for the extraction of keratin and other natural polymers from their unprocessed forms (Donato and Mija, Polymers,2020).
However, there are also some defects, such as low solubility, long dissolution time, high price, and so on (Ghosh, et al,2014, Wang and . Cao 2012, Ji, et al,2012, Idris, et al,2013).
Reducing Chemicals
The reduction process in this method is preferred more often than oxidizing agents due to its quick ability to extract keratin proteins.(Holkar et al, 2017). The most productive keratin extraction is achieved through the use of 2-mercaptoethanol, but its high toxicity and cost make it an unpopular choice. (Holkar et al, 2017, Sinkiewicz et al, 2017).
Conventional formulations containing 2-mercaptoethanol, sodium hydroxide, and sodium sulfide have historically excluded keratins due to their insoluble nature.( Sharmaetal,2018, Schrooyen, et al 2000).
Eco-friendly keratin
In addition to being inexpensive, having strong mechanical properties, and low density, extracted keratin is also non-abrasive, biodegradable, and insoluble in organic solvents (Mahmood Ismail, et al 2019). Along with being insoluble in water, weak acids, and bases, keratin is also highly strong duedisulphideisulfide bonds that hold its cysteine molecules together (Kamarudin, et al,2017).
FAQ’S
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CONCLUSION
Properly managing chicken feathers can result in a resource that benefits both environmental sustainability and the circular economy. Expanding knowledge and investigation into agricultural waste can produce valuable substances, leading to economic gains and environmental benefits.