Polyamide synthesis by hydrolases

PhD ceremony: Mr. L.W. Schwab, 13.15 uur, Academiegebouw, Broerstraat 5, Groningen

Thesis: Polyamide synthesis by hydrolases

Promotor(s): prof. K. Loos

Faculty: Mathematics and Natural Sciences

In the past decades enzymes have become part of the chemists’ toolbox and they have proven to be effective in different organic reactions. Polymers produced by enzymes include polysaccharides, polyesters and even vinyl polymers. The synthesis of polyamides by enzymatic pathways is however not extensively studied. This project was started to synthesize polyamides by enzyme catalysis.

The enzymatic (Candida antarctica lipase B) ring-opening polymerization of b-propiolactam a 4-membered lactam ring in toluene is introduced. Optimally, the enzyme is dried for 24 hours over P2O5. A reaction at 55 °C yields enzyme with the highest DP.

Enzymatic catalysis can also be applied to the polycondensation of diesters and diamines. The polycondensation diesters and diamines is followed with ATR-FTIR spectroscopy over time. A comparison is made between the rate of amide formation by the uncatalyzed reaction and by the enzymatic reaction. At 60 °C the enzymatic reaction is slower than the non-catalyzed reaction.

Papain, a protease, catalyzes the homopolymerization and copolymerization of amino acid esters. Four hydrophobic amino acids were used, tyrosine, leucine, phenylalanine and tryptophan. A detailed analysis of the composition is done by MALDI-ToF mass spectrometry. When the chains grow longer in general more leucine is present and less tryptophan is incorporated in the chains. Tyrosine is slightly more reactive than phenylalanine. Phenylalanine produces short chains with apparently a low solubility.

Papain is able to synthesize amide bonds between amino acids and diamines. A series of monoamides based on protected glycine, phenylalanine and leucine and aromatic diamines can be synthesized catalyzed by papain.