FATE OF RESIDUAL XYLANASE AFTER TREATMENT AND BLEACHING OF SOFTWOOD KRAFT PULP

A series of experiments was conducted to assess the level of enzyme pr esent in both pulp and filtrate after each step of a conventional blea ching sequence with xylanase prebleaching. Two types of assays, xylana se activity using the DNS method and radiolabelling, were used to trac e the fate of a xylanse from Streptomyces lividans, from its addition at the brownstock stage through to the end of the bleaching sequence. Results showed that the majority of the enzymatic activity disappeared from the pulp after the first caustic extraction, and no activity was detected after the first chlorine dioxide stage. In contrast, radiola belled enzyme was still detected after the second caustic extraction, but had completely disappeared again after the final chlorine dioxide stage.