Immobilization of Alcohol Dehydrogenase on Titania Nanoparticles To Enhance Enzyme Stability and Remove Substrate Inhibition in the Reaction of Formaldehyde to Methanol

Both physical and chemical procedures were applied to immobilize yeast alcohol dehydrogenase (yADH) on titania nanoparticles. It was found that chemical immobilization is an authentic method due to providing a strong bond between the enzyme and the support. The immobilization was confirmed by Fourier transform infrared spectroscopy and transmission electron microscopy. The immobilization parameters such as enzyme concentration, time of immobilization, and glutaraldehyde concentration were optimized based on the maximum immobilization yield and the best enzyme catalytic performance. Activity and kinetics of yADH before and after immobilization were studied, and the stability of enzyme at different pHs and temperatures was investigated. The optimum pH for the incubation and activity of yADH was obtained at 7.0, and the activity of immobilized yADH reached more than 80% of its initial activity after 30 days of storage at 4 degrees C. The reusability of yADH was improved by immobilization as revealed by retaining 84% of its initial activity following 10 cycles. Finally, we suggested that the immobilization of yADH is a promising method for the removal of substrate inhibition in the reaction of formaldehyde to methanol.