SUBSTRATE REACTIVITY AS A FUNCTION OF THE EXTENT OF REACTION IN THE ENZYMATIC-HYDROLYSIS OF LIGNOCELLULOSE

In an effort to better understand the role of the substrate in the rap id fall off in the rate of enzymatic hydrolysis of cellulose with conv ersion, substrate reactivity was measured as a function of conversion. These measurements were made by interrupting the hydrolysis of pretre ated wood at various degrees of conversion; and, after boiling and was hing, restarting the hydrolysis in fresh buffer with fresh enzyme, The comparison of the restart rate per enzyme adsorbed with the initial r ate per enzyme adsorbed, both extrapolated back to zero con version, p rovides a measurement of the substrate reactivity without the complica tions of product inhibition or cellulase inactivation. The results ind icate that the substrate reactivity falls only modestly as conversion in creases. However, the restart rate is still higher than the rate of the uninterrupted hydrolysis, particularly at high conversion. Hence we conclude that the loss of substrate reactivity is not the principal cause for the long residence time required for complete conversion. ( C) 1997 John Wiley & Sons, Inc.