Preparation of porous chitin beads from waste crayfish shell and application in the co-immobilization of PLP and its dependent enzyme

In this study, co-immobilization of PLP and its dependent enzyme were investigated using a novel type of porous chitin bead (PCB). Crayfish shell was used to prepare PCB via dissolution of it to form beads, followed by the removal of CaCO 3 and protein in-situ. Scanning electron microscopy, Fourier transform infrared spectroscopy , and Brunauer-Emmett-Teller method showed that the PCB had abundant porous structures with deacetylation degree of 33 % and the specific surface area of 35.87 m 2 /g. Then, the beads are used to co-immobilize pyridoxal 5-phosphate (PLP) and l -lysine decarboxylase fused with chitin-binding protein ( Sp LDC-ChBD). Laser scanning confocal microscopy revealed that the beads could co-immobilize PLP and Sp LDC-ChBD successfully. In addition, a packed bed was also constructed using the PCB containing co-immobilized Sp LDC-ChBD and PLP. The substrate conversion remained at 91.09 % after 48 h with 50 g/L  l -lysine, which showed good continuous catalysis ability. This study provides a novel method for co-immobilization of enzyme and PLP, as well as develops a new application of waste crustacean shells.