Biopolymers are polymeric materials that are produced through biological processes rather than through conventional chemical processes. Unlike traditional plastics that are derived from petroleum, biopolymers are produced from renewable biological sources like plant material or microbiological fermentation of sugars and starch. These environmentally sustainable materials have a bright future and hold promise to replace conventional plastics in many applications.

What are Biopolymers?

Biopolymers are polymers synthesized or secreted by living organisms. Common examples of biopolymers include cellulose, starch, lignin, chitin, proteins, alginates and pectin. Unlike conventional plastics, these materials are produced through natural biological processes rather than chemical synthesis. Some key types of biopolymers and their sources include:

- Cellulose: Found in plant cell walls from sources like wood, cotton or hemp. It is the most abundant natural polymer on earth.

- Starch: Stored polysaccharide in plants like corn, potatoes, rice and wheat.

- Chitin: Structural component in exoskeletons of insects and crustaceans.

- Proteins: Secreted or synthesized by all living cells from amino acid building blocks. Examples are wool, silk and collagen.

- Polylactic acid (PLA): Produced through fermentation of plant-based sugar sources like corn starch or sugarcane.

- Polyhydroxyalkanoates (PHAs): Accumulated as intracellular carbon and energy storage compounds in microorganisms.

Renewable and Sustainable

Unlike petroleum-derived plastics, Biopolymers are renewable as they are produced from biological sources that can be regrown or replenished relatively quickly through agricultural processes or biomass cultivation. They also have advantages in terms of sustainability since biological waste streams or byproducts can serve as feedstocks. For instance, cornstarch or sugarcane residues from food production can be used to make PLA biopolymers. Their production does not rely on diminishing reserves of fossil fuels.

Properties Depend on Source

The properties of biopolymers strongly depend on their original biological source. For example, cellulose is strong, stiff and rigid whereas starch is more flexible and easily deformable. Proteins can exhibit high strength or flexibility depending on their amino acid sequence and structure. Biopolymers may have properties comparable or even superior to traditional plastics. For example, PLA is almost as strong as petroleum-based polypropylene but is biodegradable. Properties can also be modified through blending of biopolymers or chemical modification of functionality.

Applications in Food Packaging

Due to their biodegradability and renewable nature, biopolymers are increasingly gaining popularity for food packaging applications as alternatives to petroleum-based plastics. For instance, PLA is used to make flexible films, rigid containers and disposable cutlery. Starch-based bioplastics are employed for making edible films and coatings. Cellulose nanocomposites can provide gas barriers for packaging fresh food. Alginate and other biopolymers help extend shelf-life through controlled release of antimicrobials. Their processing is also compatible with existing packaging machinery. Such applications help promote sustainability in the packaging sector.

Biomedical Applications

Biopolymers are also promising materials for biomedical applications due to their biodegradability and biocompatibility. For example, regenerated cellulose is used as absorbable surgical sutures. Collagen, gelatin and fibrin serve as scaffolding for tissue engineering. Chitin and chitosan possess wound healing properties. PHA nanoparticles have potential in targeted drug delivery. Their degradation by-products are easily metabolized by the body and do not require removal. The application of biopolymers in this area helps avoid long-term implantation of synthetic non-degradable materials.

New Developments and Challenges

Research on biopolymer development focuses on improving production methods, extracting high-value fractions, genetic engineering of feedstocks and modifying properties through chemical or physical treatments. New sources of biopolymers are also being explored like algae and bacteria. Blends with synthetic polymers expand the range of properties that can be achieved. However, large scale production at competitive costs remains a challenge compared to fossil-fuel based plastics. Standardization, regulatory approval and consumer acceptance for new applications also need to be addressed. With continued improvements and innovation, biopolymers are poised to play an increasingly important role alongside traditional plastics in the future.

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