Enzyme‐Catalyzed Laurolactam Synthesis via Intramolecular Amide Bond Formation in Aqueous Solution

Abstract

AbstractLactam formation from ω‐aminocarboxylic acids is thermodynamically unfavored in aqueous solution and therefore hard to achieve. In the present work ω‐laurolactam hydrolases from Acidovorax sp. T31 and Cupriavidus sp. U124 were investigated regarding their potential to catalyze lactam formation. Both enzymes are known to hydrolyze laurolactam to 12‐aminododecanoic acid. The ω‐laurolactam hydrolase genes were expressed in Escherichia coli BL21 (DE3) and the catalytic activity of the respective proteins was investigated. As expected from thermodynamics, only laurolactam hydrolysis but not 12‐aminododecanoic acid cyclization was observed in whole‐cell biotransformations and cell extract assays. The utilization of 12‐aminododecanoic acid methyl ester, as an activated form of 12‐aminododecanoic acid, resulted in intramolecular amide bond formation with the product laurolactam. Maximum laurolactam formation rates of 13.5 and 14.3 U gCDW−1 and molar yields of 11.5% and 13.0% were achieved in biotransformations at pH 10 with recombinant E. coli harboring the ω‐laurolactam hydrolase from Cupriavidus sp. U124 and Acidovorax sp. T31, respectively. Furthermore, it was shown that under the harsh reaction conditions applied, the utilization of whole‐cell biocatalysts enables 17.2‐fold higher laurolactam formation activity in comparison to free enzymes in solution. This study shows that hydrolase‐catalyzed laurolactam synthesis can be achieved in aqueous solution by selection of an appropriate substrate and reaction pH.