Study on the enzymatic bleaching of kraft pulp

为了明确白腐真菌在纸浆生物漂白系统中长期培养过程中分泌的细胞外酶的作用，我们开发了一种使用膜过滤器的培养系统，该系统可以防止菌丝与硫酸盐纸浆直接接触，但允许细胞外酶攻击硫酸盐纸浆。体外处理5 d后，sordida Phanerochaete YK-624使牙髓亮度提高21.4点，达到54.0%，显著高于黄孢Phanerochaete chrysosporium和corolus versicolor。这些结果表明，来自体外漂白系统的无细胞、膜过滤成分能够去除未漂白的硫酸盐纸浆。能够脱木质素和漂白硫酸盐纸浆的过滤试剂的明显候选是过氧化物酶和酚氧化酶蛋白质。在真菌YK-624的体外漂白过程中，可过滤成分中分泌的锰过氧化物酶活性显著。观察到锰过氧化物酶水平与纸浆光亮度呈正相关。

To Clarify the role of the excreted extracellular enzymes during long-term incubation in a pulp biobleaching system with white-rot fungi, we have developed a cultivation system using a membrane filter which can prevent the direct contact between hyphae and kraft pulp, but allows extracellular enzymes to attack the kraft pulp. Phanerochaete sordida YK-624 brightened the pulp 21.4points to 54.0% brightness after 5-day in vitro treatment, which was significantly higher than phanerochaete chrysosporium and Coriolus versicolor did during 7-day treatment. These results indicate that cell-free, membrane-filtered components from the in vitro bleaching system are capable of delignifying unbleached kraft pulp. Obvious candidates for filterable reagents capable of delignifying and bleaching kraft pulp are peroxidase and phenoloxidase proteins. Secreted manganese peroxidase activity in the filterable components was substantial during the fungus YK-624 in vitro bleaching. A positive correlation between the level of manganese peroxidase and brightening of the pulp was observed.