Development of an efficient biocatalytic system based on bacterial laccase for the oxidation of selected 1,4-dihydropyridines

Biocatalytic oxidations mediated by laccases are gaining importance due to their versatility and beneficial environmental effects. In this study, the oxidation of 1,4-dihydropyridines has been performed using three different types of bacterial laccase-based catalysts: purified laccase from Bacillus licheniformis ATCC 9945a (BliLacc), Escherichia coli whole cells expressing this laccase, and bacterial nanocellulose (BNC) supported BliLacc catalysts. The catalysts based on bacterial laccase were compared to the commercially available Trametes versicolor laccase (TvLacc). The oxidation product of 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate was obtained within 7-24 h with good yields (70-99%) with all three biocatalysts. The substrate scope was examined with five additional 1,4-dihydropyridines, one of which was oxidized in high yield. Whole-cell biocatalyst was stable when stored for up to 1-month at 4 degrees C. In addition, evidence has been provided that multicopper oxidase CueO from the E. coli expression host contributed to the oxidation efficiency of the whole-cell biocatalyst. The immobilized whole-cell biocatalyst showed satisfactory activity and retained 37% of its original activity after three biotransformation cycles.