Highly efficient ring-opening polymerization of ɛ-caprolactone catalyzed by a recombinant Escherichia coli whole-cell biocatalyst

Abstract

This paper discussed the use of a recombinant Escherichia coli whole-cell biocatalyst harboring a thermophilic lipase gene from Fervidobacterium nodosum in the catalytic synthesis of polyesters. The ring-opening polymerization of ɛ-caprolactone was used as a model reaction to study the effects of temperature and reaction medium on monomer conversion and the molecular weight of the product. The whole-cell biocatalyst displayed high catalytic activity at high temperatures (70–90°C), with almost 100% monomer conversion. Meanwhile, high monomer conversion values (>97%) were achieved in both hydrophobic and hydrophilic solvents, with the exception of dichloromethane (85%). Poly(ɛ-caprolactone) was obtained in 100% monomer conversion, with a number-average molecular weight of 2000g/mol and a polydispersity index of 1.47 in cyclohexane at 70°C for 72h. Furthermore, the whole-cell biocatalyst exhibited excellent operational stability, with monomer conversion values exceeding 90% over the course of 10 batch reactions. To verify the practicality of the procedure, scale-up reaction was also performed with isolated yield and number-average molecular weight of ca. 70% and 2140g/mol, respectively.