Skip to content

| II. - ABOUT |

,,What is keratin? And why to use the keratin?Well known that protein is a part of every cell in living organism’s body which plays many different roles to keep living things alive and healthy. The importance of protein for the growth and repair of muscles, bones, skin, tendons, ligaments, hair, eyes, and other tissues is proven since a very long time. Proteins also exist in the form of enzymes and hormones needed for metabolism, digestion, and other important processes. Natural proteins are purified from natural sources. Keratin is among the most copious proteins found associated with the body of reptiles, birds, and mammals. It is a structural constituent of nail, wool, feathers, and hoofs which offers strength to body and muscles. Nowadays, the keratin-richwaste biomass produced from poultry and meat industry imposes serious threat to environment and living beings. We need to explore various techniques and methods for the extractions and use of keratin fromwaste biomass. From the industrial point of view, keratin is a useful product in the medical, pharmaceutical, cosmetic, and biotechnological industries. Materials obtained from keratin may be converted into porous foam of different sponges, shapes, coatings, mats, microfibers, gels, and materials of high molecular weight." Swati Sharma, Arun Gupta and Ashok Kumar

TYPES OF KERATIN

α-keratins

Wool, quills, hair, horns, fingernails, hooves

  • α-keratins are made of two sub-filaments: the acid keratin (Type I) with molecular weights of 40 and 50 kDa and the neutral or basic keratin (Type II) with molecular weights of about 55–65 kDa. α-keratins are found in mammalian body parts and tissues such as wool, hair, nails, horn and hooves. Instead, the β-keratins are characteristic of nails, claws, shells and beaks of birds and they are made of 10 kDa units.
  • Up to 95% by weight of wool is made of pure keratin; in particular, the wool cortex (85% of weight fibre) is composed of intermediate-filament proteins (IFPs, characterized by a predominantly α-helical structure embedded in a matrix of high-sulphur keratins made of β-sheet and amorphous structures.
  • Alpha-keratins are the exclusive form of keratin found in humans and the wool of other mammals. The structure of the alpha-keratin is fibrous and helical, and both types I and II keratins can fall under the category of alpha.

β-keratins

Feathers, avian beaks and claws, reptilian, claws and scales

  • Beta-keratins are categorized as polypeptide chains and are only found in birds and reptiles, although those species can also possess alpha-keratins. They have been a large contributor to the overall evolution of birds throughout history. Both alpha and beta keratins help these animals maintain the composition of their claws, scales, beaks, skin, and feathers.

TYPE I.

  • Type I keratins are categorized as being the smaller and more acidic type of keratin. They are separated into two groups that work together functionally towards the common goal of epithelial cell health.

TYPE II.

  • Type II keratins are larger than their type I counterparts and have a neutral pH, which can help balance out the pairings of both types when they are synthesizing proteins and regulating cell activity.

STRUCTURE

  • The structure and function of keratin proteins are determined by their amino acid chains. These chains are very similar in species across the board. Humans share similar amino acid sequences with bovine species and rats.

  • Keratin cannot be dissolved in water, solvents, acids, or alkalines, so its structure remains largely intact when exposed to many of the body's chemicals. Keratin proteins rely on hydration (water) to maintain their overall size and function. To put this into context, wool is full of keratin. When a wool sweater is washed in heated water, it shrinks. This is because the keratin proteins lose their length when some of the molecular bonds break at high temperatures.

  • Keratin is insoluble in polar and nonpolar solvents and has very low chemical reactivity. At low pH, high temperature and in presence of reducing agents the solubility of the keratin are increased. The biodegradability and nontoxic nature of keratin make it versatile biopolymer which can be modified and extended in various forms such as films, gel, beads, and nano/microparticles.

SOURCE

The α-keratins are rich in cysteine and contain a lower number of hydroxyproline and proline amino acids: these are largely found in soft tissues, such as wool, skin and hair. β-keratins are rich in alanine and glycine, but poor in cysteine, hydroxyproline and proline: these proteins are mostly found in hard tissue, such as bird feathers, fish scales, nails and others. Keratin is classified as soft and hard forms based on their sulphur content. Soft keratin has lower cystine content, weak cross-linking and is found in hairs core and outer layer of epidermis. Hard keratin has higher cystine content, higher crosslinking degree and it is found in mammalian epidermal appendages, such as horns, hairs, nails, and in avian or reptilian tissues. The modified keratin has plenty of applications in food sciences, green chemistry, cosmetic industries, and pharmaceuticals.

KERATIN CONTENT

Hair Fur Wool Feathers Silk Skin Hooves
90 % x % 95 % 90 % 75–80 % 80 % x %
Hair Fur Wool Feathers Silk Skin Hooves
x % x % 90-95 % x % x % 25–35% % 44 %

CYSTEIN CONTENT

Hair Fur Wool Feathers Silk Skin Hooves
x % x % 11-17 % 7 % x % x % x %

WHY?

Among natural sources, protein-based materials are widely considered for biotechnological applications. keratin is one of the most promising protein to be exploited for the design of advanced biomaterials, due to:

  • Keratin is an efficient adsorbent of heavy metals and volatile organic compounds, thus useful for water and air purification.
  • Its intrinsic bioactive properties, such as the ability to promote cells adhesion and proliferation, allow a wide range of medical applications.
  • Due to its flame retardant and gas barrier properties, keratin represents a very promising biomaterial for the development of compostable food packaging.
Last update: 2022-05-10