Enhancing Catalytic Activity and Stability of Yeast Alcohol Dehydrogenase by Encapsulation in Chitosan-Calcium Phosphate Hybrid Beads

A kind of calcium phosphate-mineralized chitosan beads (chitosan–CaP) was prepared via a one-pot method by adding droplets of Ca2+-containing chitosan aqueous solution into phosphate-containing sodium tripolyphosphate aqueous solution. The chitosan beads formed immediately coupled with in situ precipitation of calcium phosphate on the surface. The antiswelling properties of hybrid beads were greatly improved with the swelling degree as low as 5%. The morphology of the resultant chitosan–CaP hybrid beads was observed by scanning electron microscopy (SEM). Yeast alcohol dehydrogenase (YADH) was encapsulated in the hybrid beads with an about 40% lower enzyme leakage compared with that in the pure chitosan beads. The optimal temperature and pH value for enzymatic conversion catalyzed by YADH immobilized in the chitosan–CaP beads were 30 °C and 7.0, respectively, which were identical to those for free YADH. The immobilized YADH displayed obviously higher thermal stability, pH stability, recycling stability, and storage stability than the free YADH counterpart.