Role of fragmentation activity in cellulose hydrolysis

Most studies of cellulose hydrolysis have been carried out on three components of the cellulolytic systems, viz, endoglucanases, exoglucanases, and cellobiases. Little attention has been paid to the fragmentation activity of certain cellulolytic systems. We have noticed that despite being a more powerful degrader of modified cellulose (CMC), the 7-day grown culture filtrate of Myrothecium verrucaria was less effective than that of Trichoderma reesei at degrading pure unmodified cellulose. Scanning electron microscopy imaging showed that one distinguishing feature of the latter is its ability to fragment (macerate) the cellulose. Cellulose particle size decreased with time as it was incubated in the culture filtrate of T. reesei at 37 °C. This was used as a pre-treatment. Pre-treated cellulose was then washed and incubated with fresh T. reesei or M. verrucaria culture filtrates. Pre-treatment increased liberation of reducing sugars during subsequent incubation of cellulose in T. reesei culture filtrate but not in subsequent incubation in M. verrucaria culture filtrate. It was hypothesized that fragmentation activity of the pre-treatment opened up attack sites for further hydrolysis, but these were not available for attack by other enzyme systems.