Enzymatic hydrolysis of microcrystalline cellulose in an oscillatory baffled reactor (OBR) and a parallel stirred tank (STR) were studied. In the proposed mechanistic model, saccharification of the intractable, crystalline portion of cellulose, E*Sx is important. Its rate, k3 (0.002), although much lower than k2 (9.05), the rate of product formation from the active E * Sc intermediate, makes appreciable contribution to the final glucose yield in the saccharification of cellulose. Shear deactivation of the cellulase is also considered in relation to average shear rate (ASR) in the reactor. At 200 Wm-3 ASR in the STR was twice that in the OBR (45:22.5 s -1 respectively). Correspondingly, 74% saccharification of cellulose was observed in the STR and 91% in the OBR after 168 h. The OBR has a more uniform shear field than the STR, hence, lower ASR even at the same power density as the STR. The OBR achieved the highest conversion at ~1/20th the power input of