In Situ Generation of Mediator - A New Concept for Laccase-Catalyzed Delignification of Kraft Pulp, 2000 Pulping / Process & Product Quality Conference Proceedings

M. Amann, A. Candussio, R. Muller, V. Frey, M. G. Paice, R. Bourbonnais, S. Labonte, G. Sacciadis, S. Renaud--A very promising laccase mediator system (LMS ® ) had been developed with N-OH-acetanilide (NHA) as the mediator component. However, the high cost due to high mediator dosage and the potential for generating toxic by-products are concerns when implementing such a process in a mill’s bleaching sequence. Changing the system from a batch process to a continuous dosing technology can solve both of these problems. To adapt the proposed new procedure to existing mill equipment, a diacetylated mediator precursor was developed (DiAc; N-acetoxy-N-phenylacetamide), which generates NHA during the laccase stage (L). Mild alkaline conditions are optimal for the L-stage with DiAc to assure a quantitative NHA release. The process was analyzed in the lab first, and then transferred to a pilot plant scale. Due to the pH requirements laccase from Myceliophthora thermophila was used. Running a five stage ECF sequence LEpD0EoD1 produced a pulp comparable to a mill reference pulp (D0EopD1EpD2) with significant saving of bleaching chemicals (8,5 kg/tonne). Further work is required to develop an enzyme that is optimal for the DiAc mediator reaction conditions.