Thermodynamic, kinetic, and operational stabilities of yeast alcohol dehydrogenase in sugar and compatible osmolyte solutions

Thermodynamic, kinetic, and operational stabilities of yeast alcohol dehydrogenase (YADH) were measured and compared in aqueous solutions containing various sugars (sucrose, glucose, and ribose) and compatible osmolytes (betaine and sarcosine). In the measurement of operational stability, native YADH was entrapped and physically immobilized in an ultrafiltration hollow fiber tube to retain the native characteristics of the enzyme. All the additives tested increased thermodynamic stability and kinetic stability of YADH. The order of the magnitude of stabilization effect among additives was different between thermodynamic and kinetic stabilities. Compared to the thermodynamic and kinetic stabilities, the effects of additives were much different in operational stability. Sucrose, glucose, and betaine stabilized YADH substantially while ribose and sarcosine destabilized the enzyme. These results show that the thermodynamic and kinetic stabilities do not necessarily guarantee the operational stability of YADH. The coexistence of stabilizing solute was proved effective to increase the productivity of the bioreactor with immobilized YADH.