New pulp biobleaching system involving manganese peroxidase immobilized ina 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 t he enzyme's low stability. We developed a new pulp biobleaching method invo lving mesoporous material-immobilized manganese peroxidase from Phanerochae te chrysosporium, MnP immobilized in FSM-16, a folded-sheet mesoporous mate rial 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 co ntinuous reaction, We constructed a thermally discontinuous two-stage react or system, in which the enzyme (39 degreesC) and pulp-bleaching (70 degrees C) reactions were performed separately. When the treatment of pulp with MnP by means of the two-stage reactor system and alkaline extraction was repea ted seven times, the brightness of the pulp increased to about 88% within 7 h after completion of the last treatment.