The effect of shaking regime on the rate and extent of enzymatic hydrolysis of cellulose

In an attempt to elucidate the effect of mixing on the rate and extent of e nzymatic hydrolysis of cellulosic substrates, alpha -cellulose was hydrolys ed using a commercial cellulase preparation at varying levels of substrate concentration (2.5,5 and 7.5% (w/v)) and by using three shaking regimes: co ntinuous at low-speed (25 rpm), continuous at high-speed (150 rpm) and an i ntermittent regime comprised of high and low-speed shaking intervals. The c ontinuous, high-speed shaking produced the highest conversion yields, where as the intermittent and low-speed shaking regimes resulted in lower convers ions. After 72 h, at all shaking regimes (150 rpm, 25 rpm and intermittent) , using a low substrate concentration (2.5%) produced conversion yields (82 , 79 and 80%) higher than those obtained at high (7.5%) substrate concentra tion (68, 63 and 68%). As the substrate concentration increased, the conver sion yields at intermittent shaking gradually approached those resulting fr om high-speed shaking. Thus, it appears that intermittent shaking could be a beneficial process option as it can reduce the mixing energy requirements while producing reasonably high conversion yields. (C) 2001 Elsevier Scien ce B.V. All rights reserved.