Application of fungi in biotechnological processes for the pulp and paper industry

[摘要] English: Lignin, hemicellulose and cellulose occur together in wood and agriculturalwastes that are used in industries such as the pulp and paper industry. Biodegradationcould be applied by these industries to save cost and reduce environmental impact.Lignocellulose degradation is very complex and must be understood for the optimisationof biotechnological processes. White-rot fungi degrade lignin, cellulose andhemicellulose while brown-rot fungi modify lignin slightly, but also break down celluloseand hemicellulose. The most important enzymes in lignin degradation are manganeseperoxidase, lignin peroxidase and laccase, which these fungi produce extracellularly.Decay fungi establish on organic material, which leads to the degradation oflignocellulose during the colonization process. A distinction must be made betweenprimary and secondary colonisers during degradation, because of succession that takesplace. Ophiostoma piliferum is an example of a primary coloniser, which is used toproduce Cartapip 9if). This product was developed to treat wood chips during storage toreduce fibre degradation. The fungus was previously not available in South Africabecause of a possible threat to local forest species. South African forestry companieswanted to test Cartapip 97® in industrial processes and it was, therefore, necessary todemonstrate that the fungus is not pathogenic. It also had to be confirmed that the fungusis a strain of 0. piliferum before certification and importation into South Africa would beallowed. Cultural and morphological characteristics of the anamorph of the Cartapip fungus were found to be similar to those of O. piliferum and it was released for fieldtrials. The pathogenicity of the fungus was compared with Ophiostoma ips andSphaeropsis sapinea, causes of sapstain on Pinus spp. in South Afiica, to demonstratethat O. piliferum does not pose a threat to forestry. Different pine species wereinoculated and the results indicated that O. piliferum is not a pathogen and it is, therefore,safe to use Cartapip 9if) in South Afiica. Hardwood and softwood chips weresubsequently treated with Cartapip 97® and pulped using different pulping methods, butthe benefits were not obvious. It is, however, possible that the extractives content of thechips was reduced. A slight increase in strength of kraft pulp from softwood andhardwood and also of Soda-AQ pulp from A. mearnsii, was observed after pre-treatmentwith Cartapip 97®. Bagasse contains fibres that can be used for the production of paper. However,bagasse has to be stored for long periods during which time decay occurs. Stored bagassecould be pre-treated with fungi to preserve and possibly improve the quality of thebagasse. In this study, Lenzites betulina and Pycnoporus sanguineus were used to treatbagasse before pulping. Inoculum production, pulping processes and different incubationperiods were evaluated to optimise biopulping. Ultrastructural studies of treated bagassewere used to determine the effect that fungal treatment has on bagasse. Pulping resultsobtained from bagasse treated with L. betulina were variable and P. sanguineus did notimprove the pulping. These results indicated that colonisation and degradation strategiesof biopulping fungi must be fully understood before an attempt is made to optimizepulping processes.

[发布机构] University of the Free State