Twenty years ago synthesis of biopolymers cost more than synthesis of polymers from petroleum. However, rising prices made this sphere more attaractive. Besides, biopolymers may not only substitute traditional polymers but also possess new characteristics (biodegradability, extreme strength, possibility to obtain thin and firm films) (Sample).
There are three way of to synthesize biopolymers. The first way is an extraction and modification of natural polymers from plants. The examples of such materials are thermoplastic starch, derivatives of cellulose and rubber. Rubber obtained from the rubber tree Hevea braziliensis is the first known polymer. The second pathway is a polymerization of bio-monomers. Polylactic acid (PLA), polyamides, polyurethanes and polyesters can be obtained using this approach. The third pathway is an extraction of polymers produced by microorganisms. Polyhydroxyalcanoates (so-called PHA family) can be obtained using this approach (Rudin and Choi 528). Microorganisms can also produce monomers or raw materials that can be extracted and polymerized. For example, bioethanol can be produced from the sugarcane starch, wheat or corn through microbial strain and biological fermentation process. Afterward, ethanol is dehydrated over a solid catalyst to ethylene, which is polymerized to polyethylene (Babu, OConnor, and Seeram 6).
The production of biopolymers uses the well-known polymerization techniques. For example, polyamides or polyurethanes can be produced using free radical, cationic, olefin metathesis and condensation polymerization. Polylactic acid is obtained from lactic acid by the combination of condensation polymerization and ring opening polymerization or by one of the mentioned techniques separately. Polymers like PHA are synthesized by microorganisms (sometimes genetically modified) and extracted using centrifugation and press