New pulp biobleaching system involving manganese peroxidase immobilized in a silica support with controlled pore sizes

Attempts hare been made to use manganese peroxidase (MnP) for chlorine-free pulp biobleaching, but they have not been commercially viable because of the enzyme's low stability. We developed a new pulp biobleaching method involving mesoporous material-immobilized manganese peroxidase from Phanerochaete chrysosporium, MnP immobilized in FSM-16, a folded-sheet mesoporous material whose pore size is nearly the same as the diameter of the enzyme, had the highest thermal stability and tolerance to H2O2. MnP immobilized in FSM-16 retained more than 80% of its initial activity even after 10 days of continuous reaction, We constructed a thermally discontinuous two-stage reactor system, in which the enzyme (39 degreesC) and pulp-bleaching (70 degreesC) reactions were performed separately. When the treatment of pulp with MnP by means of the two-stage reactor system and alkaline extraction was repeated seven times, the brightness of the pulp increased to about 88% within 7 h after completion of the last treatment.