The use of enzyme recycling and the influence of sugar accumulation on cellulose hydrolysis by Trichoderma cellulases

The enzymatic hydrolysis of cellulose was initially investigated using the alkaline peroxide-treated fraction derived from steam-exploded Eucalyptus viminalis chips and a cellulase mixture of the commercial Celluclast and Novozym preparations. Nearly complete saccharification of the substrate was obtained when hydrolysis was carried out at a substrate concentration of 6% (w/v) and an enzyme loading of 10 FPU g−1 of cellulose. Lower rates of hydrolysis were observed when high sugar concentrations accumulated in the reaction mixture. The removal of soluble sugars liberated during hydrolysis enhanced the efficiency of hydrolysis of the residual substrate. Most of the cellulase activity was shown to be associated with the undydrolyzed residue. The enzyme mixture used to obtain complete hydrolysis of the substrate at a 2% (w/v) concentration was successfully recycled for five consecutive steps, with an elapsed time of 48 h between each recycling step. This same enzyme preparation could be reused an additional four times if the duration of hydrolysis was extended to 120 h; however, the efficiency of cellulose hydrolysis gradually decreased with each subsequent recycling step.