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 enzymatic hydrolysis of cellulosic substrates, alpha -cellulose was hydrolysed 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: continuous at low-speed (25 rpm), continuous at high-speed (150 rpm) and an intermittent regime comprised of high and low-speed shaking intervals. The continuous, high-speed shaking produced the highest conversion yields, whereas the intermittent and low-speed shaking regimes resulted in lower conversions. 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 concentration (68, 63 and 68%). As the substrate concentration increased, the conversion yields at intermittent shaking gradually approached those resulting from 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 Science B.V. All rights reserved.