Temperature dependence of cellulase hydrolysis of paper fiber

The hydrolysis of cellulosic fiber used in papermaking by cellulase enzymes was studied as a function of fiber length and temperature. The rate of hydrolysis of the fines fraction increased with temperature but that of the longer fiber was relatively temperature independent. The binding of enzyme to the fiber was proportionately almost three times higher for the fines fraction. Binding of these enzymes to cellulose is known to be inversely temperature dependent, whereas the catalytic step should have a direct dependence on temperature. It is proposed that the two effects offset each other for the longer fiber where there is more free enzyme present as compared to the situation with fines. A similar effect was noted for the hydrolysis of cellulosic paper mill sludge where the rate of hydrolysis of the longer fiber was relatively temperature independent. A practical outcome is that the cost of heating long-fiber sludges to 50 °C, the reported optimum temperature for the enzyme, can be avoided.