Deactivation and stabilization of cellulase complex

Abstract

During enzymatic hydrolysis of cellulose, the cellulase complex was found to be deactivated significantly and the utilization efficiency of cellulase for practical application was found to be very low and only 30\% of the initial enzyme activity. In order to find out the causes for the cellulase deactivation and low utilization efficiency and at the same time to find the method of stabilizing the cellulase, the effects of shear and air-liquid interface on the cellulase activity were investigated. The cellulase solution displayed rheological properties of a dilatant fluid with a consistancy factor 9.82 $10^{-5}$ and a power index 1.56. When cellulase solution was subjected to the shear by allowing it to flow through a capillary tubing and also was exposed to renewable air-liquid interface, the combined effect of shearing and air-liquid interface on the cellulase deactivation was found to be far more significant as compared to the effect of shear itself. In the presence of air-liquid interface approximately 60\% of cellulase activity was lost after 4hr shearing at 850 $\sec^{-1}$, while no measurable deactivation was observed at the same condition but without interface. It was also found that with increasing cellulase concentration, deactivation due to the presence of air-liquid interface decreased. The effect of air-liquid interface was considered to be primarily on adsorbed protein at the interface. And the dependence on protein concentration was explained by the point that the ratio of surface excess to bulk protein decreases as the protein concentration increases in the constant surface excess region. Some surface active agents were tested of its stabilizing effect on cellulase with air-liquid interface and at 850 $\sec^{-1}$. Zonyl FSN, Triton X-100, and bovine serum albumin turned out to be effective such that nearly no deactivation was observed after 4 hr shearing with air-liquid interface. The effect of Zonyl against surface deactivation was possibly due ...