A review on enzymatic polymerization to produce polycondensation polymers: The case of aliphatic polyesters, polyamides and polyesteramides

Enzymatic polymerization represents today an effective and preferable alternative to conventional chemically-catalyzed processes. It offers significant advantages, summarized in the applied mild reaction conditions mainly in terms of temperature and toxicity, and high selectivity of enzymes, avoiding protection-deprotection strategies and resulting in improved qualitylperformance of end products. Especially for polycondensation polymers, biocatalyzed synthetic routes have been under research for the last thirty years, including homo- and copolymerization of a significant number of monomers. Aliphatic polyesters, polyamides and at a much lower extent polyesteramides, represent the core of the pertinent studies, and are systematically discussed in the current review. Emphasis is given on polycondensates with biodegradability properties, derived from bio-based monomers such as succinic acid, 1,3- propanediol and lactide/lactic acid. Free or immobilized lipases and cutinases are the predominant biocatalysts in the relevant polymer families, being used in polycondensation as well as in ring-opening reaction schemes. The efficiency of the different biocatalytic processes is herein correlated to important process parameters, such as the enzyme and monomer type, the reaction temperature and time, the polymerization technique (solution or solvent-free), as well as the by-product removal method, e.g., application of vacuum, water absorption by molecular sieves, azeotropic distillation. (C) 2017 Elsevier B.V. All rights reserved.