# Enzymatic Synthesis of Biobased Polyesters and Polyamides
## 1 Polymers: From Petrol-Based to Biobased and Beyond
Considering the rich abundance of biomass feedstocks in nature, it is of great interest to produce biobased polymeric materials by chemical or physical modifications of natural polymers, or from biobased molecules that are converted from biomass feedstocks. Actually human beings already used the former approach long time ago during the 1800s. Many commercially important polymers are prepared via this approach, for example, vulcanized natural rubber, gun cotton (nitrocellulose), cellulose esters and cellulose ethers. However, chemical and physical modifications of natural polymers are often subject to the poor solubility and process difficulty of natural polymers, as well as, unwanted impurities within the network of natural polymers which are hard to remove. On the other hand, conversion of biomass feedstocks to end-products is a promising pathway for the production of high tonnage consumer polymeric products such as paper, paints, resins and foams [11]. For instance, oleochemicals can be converted from vegetable oils and fats, which are biobased building blocks for the production of thermoset resins and polyurethane. However, the obtained biobased polymeric materials often possess diverse chemical structures; and it is nearly impossible to produce biobased polymers with identical structures as the petrol-based counterparts, due to the use of biomolecule mixtures. Besides, some unwanted structures or impurities might be inherited from the biomolecule mixtures, which might greatly influence the properties and applications of the final polymeric materials. Utilization of biobased monomers with tailored structures in polymer synthesis is the most promising approach towards biobased polymers, which can result in not only sustainable alternatives to petrol-based counterparts with similar or identical structures, but also in novel green polymers that cannot be produced from petrol-based monomers [5; 8; 9; 14; 15; 16]. However, this is also the most expensive approach of all three as aforementioned. Benefiting from solar energy, numerous biobased monomers can be produced from yearly-based biomass feedstocks via biocatalytic or chemo-catalytic processes, which provide a great opportunity to access diverse biobased polymers [5; 7; 8; 9; 10; 11; 14; 15; 16; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27]. Meanwhile, more and more biobased monomers are already or will become commercially available in the market due to the fast development of biotechnologies and their price will be competitive with that of the petrol-based chemicals [28; 29; 30; 31; 32; 33; 34]. Enzymatic polymerization is an emerging alternative approach for the production of polymeric materials, which can compete against conventional chemical synthesis and physical modification techniques [35; 36; 37; 38; 39; 40; 41; 42; 43; 44]. Enzymatic polymerization also provides a great opportunity for accessing novel macromolecules that are not accessible via conventional approaches. Moreover, with mild synthetic conditions and renewable non-toxic enzyme catalysts, enzymatic polymerization is considered as an effective way to reduce the dependence of fossil resources and to address the high material consumption and pollution problems in the polymer industry. At present, petrol-based monomers are still predominately used in enzymatic polymerizations. By combining biobased monomers and enzymatic polymerizations in polymer synthesis, not only the research field of enzymatic polymerization could be greatly accelerated but also the utilization of renewable resources will be promoted. This will provide an essential contribution for achieving sustainability for the polymer industry, which will eventually play an important role for realizing and maintaining a sustainable society.