Enhancing catalytic stability and cadaverine tolerance by whole-cell immobilization and the addition of cell protectant during cadaverine production

A whole-cell (cadaverine-producing strain, Escherichia coli AST3) immobilization method was developed for improving catalytic activity and cadaverine tolerance during cadaverine production. Cell-immobilized beads were prepared by polyvinyl alcohol (PVA) and sodium alginate (SA) based on their advantages in biocatalyst activity recovery and mechanical strength. The following optimal immobilization conditions were established using response surface methodology: 3.62% SA, 4.71% PVA, 4.21% CaCl2, calcification, 12 h, and freezing for 16 h at -80 degrees C, with a cell concentration of 0.3% (g dry cell weight (DCW) per 100 mL) of immobilized beads. After a 2-h bioconversion, the immobilized beads maintained 85% of their original biocatalyst activity, which was 1.8-fold higher than that of free cells. Furthermore, the effects of cell protectants on immobilized biocatalyst activity were examined by fed-batch bioconversion experiments. The results showed that the addition of polyvinylpyrrolidone (PVP) into the immobilized matrix effectively protected biocatalyst activity, with 95% of the relative activity remaining after the 2-h bioconversion. The performance of PVA-SA-PVP-immobilized E. coli AST3 showed continuous production of cadaverine, with an average cadaverine yield of 29 +/- 1 g gDCW(-1) h(-1) after 12 h, suggesting that this method is capable of industrial scale cadaverine production.