Biopolymers

Biopolymers are polymers produced from natural sources. These can either be chemically synthesised from biological materials or biosynthesised by living organisms. These are made up of monomeric units bonded together by covalent bonds. These monomeric units form larger molecules. As biopolymers are derived from living organisms like plants and microbes, they are a renewable resource, unlike most polymers which are petroleum-based polymers. 

Generally, biopolymers are degradable. They find use in various industries ranging from food industries to manufacturing, packaging and biomedical engineering. Biopolymers are promising materials owing to their characteristics like abundance, biocompatibility and unique properties like non-toxicity etc. With some nanosized reinforcements to enhance its properties and practical applications, biopolymers are being researched for its use in more and more ways possible.

Examples of biopolymers are protein, starch, cellulose, DNA, RNA, lipids, collagen, carbohydrates etc.

Types of Biopolymers

Biopolymers can be classified according to various scales. These classifications are based on their origin, a number of monomeric units, on the basis of degradability, their heat response etc. Some of the classifications are:

On the Basis of Type

1. Sugar-based polymers- Starch or sucrose is used as input for manufacturing. Lactic acid polymers are created using lactose from potatoes, maise, etc.

2. Starch-based polymers- Starch acts as a natural polymer, composed of glucose. It is found in plant tissues.

3. Cellulose-based biopolymers- Used for packaging, this polymer is made up of glucose obtained from natural sources like cotton. Eg. cellophane.

4. Synthetic materials- Degradable polymers can be made from synthetic materials obtained from petroleum.

On the Basis of Origin

1. Natural biopolymers- These are natural biopolymers biosynthesised by living organisms.

2. Synthetic biopolymers - These are polymers made up of renewable materials like polylactic acid which are degradable.

3. Microbial- Biopolymers produced by microorganisms.

On the Basis of Monomeric Units

1. Polysaccharides-These are carbohydrate chains which are branched or are linear: Eg. starch, cellulose, etc.

2. Proteins- Polymers made up of amino acids. Eg. collagen, fibrin etc.

3. Polynucleotides - Nucleic acids are long polymer chains composed of 13 or more monomeric units. Eg. DNA, RNA etc.

Difference Between Biopolymers and Synthetic Polymers

Applications of Biopolymers

Biopolymers have unique properties and are an abundant material. Due to their unique properties and structures, biopolymers find their application in many places.

Biomedical

Biopolymers are very widely used in the biomedical field. Due to the properties like degradable and non-toxic, biocompatible properties, etc., they are used in tissue engineering, pharmaceutical industry, medicines, drug delivery etc. Polypeptides are inexpensive and easily available, therefore find various uses in biomedical materials. 

Drug delivery systems- Biopolymers like collagen and chitosan are used as drug delivery systems to target the drug and improve drug absorption. Collagen sponges are widely used to treat burn wounds. Both collagen and chitosan are used in tissue engineering. These are very porous and allow the wounds to heal.

Industrial Use

Biopolymers owing to their unique properties find use as industry-standard materials. They are combined with some materials to reinforce the properties of these biopolymers to enhance their desired properties and practical applications. These are widely used in packaging; PHA, polylactic acid and starch being inexpensive and readily available are perfect for this task. They also have barrier characteristics which are not available in other polymers, like these are water-resistant.

Biopolymers are used in the automotive industry to make interior and exterior parts, electrical components, engine, exhaust, steering wheels etc. Biopolymers are added to cement during concrete preparation to increase the desired properties. They are used in the construction industry of interior decoration. Chitosan has properties that remove metals from the water which makes it usable for water purification. Due to its antimicrobial properties, it is also used at places to stop microorganism growth.

Other Applications

• Agricultural/Fishery- Fishing lines, fertilisers, beehives, nets, traps, etc.

• Electronics- In the manufacturing of audio devices, printed circuit boards, insulated wires, cables and other electronic devices.

• Cosmetics - Used for cleaning purposes, pedicure and manicure, also in cosmetic products like sunscreen, hair products, creams etc.

• Sports/Toys- Used to make sports equipment like footballs and other hollow balls, cleats, badminton, golf equipment, etc.

• Nanotechnology- Also used in the production of nanomaterials. Biopolymers have certain unique properties which make them useful in branches of science, for example - the green chemistry. 

Common Biopolymers and their uses

1. Collagen- It is a type of protein which is most abundant in humans (30%). It is made up of amino acids which are further made up of carbon, hydrogen and oxygen. Collagen contains special types of amino acids called Glycine, Proline, Hydroxyproline and Arginine. Collagen gives strength to our various body parts and also protects them. It is a major part of human’s skin and nails. As it is composed of three chains, it has a triple helix like structure. 

2. Gelatin- It is widely used in various industries due to its properties of biodegradability and biocompatibility. Gelatin is a water soluble protein which is derived from collagen (natural polymer). Its main function is to look after the connective tissues such as bones, tenders, cartilage etc. There are 16 different collagen types in the human body. The most prominent ones are the Type I, II and III or collagen I, II and III). 

3. Starch- Starch is one such biopolymer which is found in abundance. It is used widely as it is inexpensive, renewable and biodegradable. Starch is a naturally occurring biodegradable polymer which is  easily available from agriculture based activities. People use starch in the food products as well as non food products. 

4. Silk fibroin- It is another type of protein polymer which is obtained from silkworms. It is generally used in fashion textiles and medical stitching.