Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
The changes of the reactivity of cellulose during enzymatic hydrolysis and the adsorption capacity of cellulase into insoluble cellulose are two central features of several mechanistic models presented for enzymatic hydrolysis of cellulose. In the present study, these parameters were investigated for regenerated cellulose, i.e. amorphous cellulose. The regenerated pure cellulose was obtained by dissolution cotton linter in N-Methylmorpholine-N-oxide (NMMO) at 120 °C, and then regeneration by adding water. The data of adsorption of cellulase into cellulose was examined with the Langmuir isothermal model. The maximum adsorption capacity was obtained as 212, 35, and 5 mg protein/g substrate for regenerated cellulose, Avicel, and cotton, respectively. The substrate reactivity (SR) was measured while the effect of end products inhibition and also enzyme inactivation during enzymatic hydrolysis was eliminated. The SR of the regenerated cellulose was declined from 1 to 0.43 after conversion of 30% of substrate in 15 min. Then, there was no significant change in the SR until conversion of 92% of cellulose which was achieved by 6 h hydrolysis. This study shows that by regeneration of cellulose its capacity of cellulase adsorption is dramatically increased. However, the effect of reactivity of cellulose on the rate of hydrolysis is eliminated and SR may be deleted from its hydrolysis kinetic model.