One-pot fabrication of chitin-shellac composite microspheres for efficient enzyme immobilization

In this study, all-natural composite microspheres were fabricated through adding shellac into chitin solution followed by self-assembly via thermally-induced phase separation. The pore structure of the composite microspheres was altered into wedge-shape from ink-bottle-shape of the chitin microspheres, whereas, the crystalline structure of these two kinds of microspheres remained unaltered. The as-fabricated chitin-shellac composite microspheres were used for enzyme immobilization through adsorption. And yeast alcohol dehydrogenase (YADH) was chosen as the model enzyme, which is a multimer consisting of 4 subunits. The loading capacity of the as-prepared composite microspheres was up to 79.0 mg/g (enzyme/carrier). The immobilized enzyme exhibited a comparable catalytic activity compared to its free counterpart and maintained 49.3% of its initial activity after 54 days' storage at 4 °C while the free enzyme lost all its activity.