Studies on biological kraft pulping of compression-baled wood chips with lignin-degrading fungi.

摘要

Biopulping protocols have mostly been carried out on few wood species and small wood samples under highly controlled conditions involving sterilization, pure fungal cultures, optimal temperature and relative humidity, nutrient supplements and aeration. These represent technical and economic barriers to realistic applications of biopulping. The present study intended to elucidate how the compression-baling technique could best afford an alternative to fungal incubation of wood chips before kraft pulping without the need for contending with the restrictions mentioned above. Jack pine chips which had been inoculated (with Ceriporiopsis subvermispora or Phanerochaete chrysosporium), compression-baled, and stored for 45 days were cooked using various kraft pulping schedules. It was found that the former fungus facilitated a 20% reduction in total cooking time while maintaining pulp and paper properties at levels comparable to those derived from the control chips. Hydrogen peroxide bleaching showed that the brightness gains were statistically identical for the control and C. subvermispora-pretreated wood. P. chlysosporium, on the other hand, did not engender any improvements as most of the resulting paper strength properties were worse.;The ability of one of the P. chrysosporium strains to selectively degrade lignin was significantly improved when the aspen substrate blocks had been impregnated with disodium octaborate tetrahydrate or trifluoperazine (a calmodulin inhibitor) at the concentrations examined. This study indicated that the selective delignification exhibited by some white-rot fungal strains could be improved by chemically modifying the wood substrate.;Studies on the conidial germination of two P. chrysosporium strains using a contact-agar approach showed that compression of aspen chips enhanced the germination of both on sapwood, an observation that was verified on wood chips using scanning electron microscopy. This could result from a decrease in the number of viable parenchyma cells and modifications of chemical component profiles in wood after compression. The latter was confirmed by gas chromatographic analyses of acetone extracts from agar placed in contact with the wood chips. Introduction of aspen expressed liquid into the conidial suspensions led to enhanced germination rates for P. chrysosporium on heartwood chips, an effect which could be attributed to increases in the nutrient levels for the fungus.