Influencing the Activity of a Biocatalyst: The Combination of Temperature Selection and Substrate Properties Counts

Enzyme-catalyzed polyester synthesis is a promising alternative to conventional high-temperature melt polycondensations. Monomer properties significantly influence the performance of the enzyme catalyst, which depends on many other factors including temperature and immobilization technique. To understand the influences of substrate properties on the activity of Candida antarctica lipase B immobilized on Immobead 150, bulk reactions at 40, 60, or 80 °C were performed using adipic acid and aliphatic diols of differing lengths, where a constant N2 flow was employed for gentle water removal. Results from these isothermal reaction systems clearly indicate that the polarity of the diols and solubility of the acid in the reaction mixture have a major impact on the catalytic activity of the enzyme. While for the least polar long-chain diols (octanediol and decanediol) high conversions and molar masses were achieved at 80 °C, lower reaction temperatures were required for more polar diols to prevent catalyst inactivity (propanediol, butanediol, pentanediol, and hexanediol). For these substrates, temperature gradient programs were efficient in improving catalyst performance and increasing chain length. These findings highlight the importance of substrate evaluation and parameter screening, together with providing valuable insights for the application of biocatalysts in polyester synthesis.