Utilization of wood-decay fungi for biokraft pulping of softwood
| dc.contributor.advisor | Rabie, C. J. | |
| dc.contributor.advisor | Wingfield, M. J. | |
| dc.contributor.author | Wolfaardt, Jacobus Francois | |
| dc.date.accessioned | 2017-06-13T06:37:58Z | |
| dc.date.available | 2017-06-13T06:37:58Z | |
| dc.date.issued | 1999-05 | |
| dc.description.abstract | English: The forest products industry is one of the most important earners of foreign exchange for South Africa. The major focus of the industry is the production of pulp with an annual capacity of 2,4 million tons. Wood from plantations of exotic trees is the most important source of fibre, but other fibre sources are also used. Biotechnology can play a significant role in the industry to produce high value products at lower cost and could reduce the environmental impact of conventional processes. Biopulping is potentially the most important of these biotechnological processes, because it can influence all downstream operations. The aim of this study was, therefore, to develop a biopulping process for the treatment of softwood at the Sappi Ngodwana kraft mill in Mpumalanga. Initially, 278 strains of wood-decay fungi were collected from various natural habitats. This collection represents a diversity of fungal families and included species that have not previously been recorded from South Africa. The first step in selecting suitable fungal strains for biopulping was to characterize different groups on the basis of the enzymes that they produce and their oxidase reactions. The suitability of these strains for the pre-treatment of softwood chips prior to kraft pulping was subsequently assessed by evaluating their influence on kappa number, yield and strength properties of pulp. Seven of the strains tested were able to reduce the kappa number of pulp significantly, without having a significant influence on the pulp yield. These strains were more efficient than strains of Phanerochaete chrysosporium and Ceriporiopsis subvermispora that have been patented for other biopulping applications. Treatment of wood with strains of Peniophora sp., an unidentified specie as well as two strains of Stereum hirsutum resulted in pulp with improved strength properties. The envisaged biopulping process aimed at treating wood chips in outside chip storage with a biopulping fungus. The aim of one study was to investigate conditions such as temperature, moisture, CO2 and microbial populations that develop in a chip pile, and to determine the suitability of the chip pile for colonization by biopulping fungi. High temperatures and high moisture levels were observed in some areas of the chip pile, which suggested that part of the pile was unsuitable for colonization by mesophilic fungi. It will, therefore, be necessary to manage the chip pile to maintain a suitable environment for biopulping. Problems were experienced with poor colonization of freshly chipped softwood by biopulping fungi. The effect of contaminating microbes and inhibitory compounds present in wood was, therefore, studied. It was found that the inhibition of biopulping fungi by α-pinene and by contaminating microbes were both very important. The inhibition by microbes, as well as by extractives, was mitigated by a short steam treatment of wood chips. Steaming for ten minutes under atmospheric pressure could be an economical method to improve colonization by biopulping fungi. Alternatively biopulping fungi with good competitive ability and tolerance to monoterpenes could be selected. Pinus patula wood chips were pre-treated with a selected strain of Stereum hirsutum to determine the optimal conditions for the kraft pulping of pre-treated softwood and to do an economic evaluation of the process. Chips were pulped on a small scale under various pulping conditions. Lignin content, yield, and viscosity of the pulp as well as alkali consumption were evaluated. The results were used to develop models for biokraft pulping. This study showed that biopulping can reduce the kappa number of pulp or reduce the pulping time. Pulp yield losses were relatively small when pulps with low kappa number were produced. Increased alkali consumption was, however, an important factor in the economic evaluation. | en_ZA |
| dc.description.abstract | Afrikaans: Die bosbou-industrie is een van die belangrikste bronne van buitelandse valuta vir Suid-Afrika. Die industrie fokus hoofsaaklik op die produksie van pulp met 'n jaarlikse produksiekapasiteit van 2,4 miljoen ton. Die belangrikste roumateriaal vir die industrie is hout uit plantasies van uitheemse bome, maar ander bronne word ook benut. Biotegnologie kan 'n belangrike rol in die industrie speel om hoë-waarde produkte te vervaardig teen 'n laer koste en om die omgewingsimpak van konvensionele prosesse verminder. Bioverpulping is potensieël die belangrikste metode, omdat alle verdere vervaardigingsprosesse daardeur beïnvloed word. Die doel van hierdie studie was dus om 'n bioverpulpingsproses te ontwikkel vir die behandeling van sagtehout by die Sappi Ngodwana kraft-meule in Mpumalanga. Aanvanklik is 278 isolate van witvrot fungi versamel uit verskillende natuurlike habitatte. Hierdie versameling het 'n verskeidenheid fungus families verteenwoordig en het ook spesies ingesluit wat nie voorheen in Suid-Afrika beskryf IS me. Die eerste stap om geskikte isolate vir bioverpulping te kies, was om verskillende groepe te karakteriseer in terme van hulle produksie van ensieme en oksidase-reaksies. Die geskiktheid van hierdie isolate vir die behandeling van houtskerfies voor kraft-verpulping is vervolgens beslis deur hulle invloed op kappagetal, opbrengs en sterkte van pulp te bepaal. Sewe van die isolate wat getoets is, het die kappagetal van pulp betekenisvol verlaag sonder om pulpopbrengs betekenisvol te verlaag. Hierdie isolate was meer doeltreffend as isolate van Phanerachaete chrysasparium en Ceripariapsis sub vermispara, wat vir ander toepassings van bioverpulping gepatenteer is. Behandeling van die hout met 'n isolaat van Peniophora sp., 'n isolaat wat nie geidentifiseer is nie en twee isolate van Stereum hirsutum, het pulp met verbeterde sterkte-eienskappe gelewer. Die voorgestelde bioverpulpingsproses het ten doel gehad om houtskerfies met die bioverpulpingsfungus te behandel waar dit in die buitelug gestoor word. Die doel van een studie was om toestande soos temperatuur, houtvog, C02 en populasies van mikrobe te ondersoek, sodat die geskiktheid van die hope vir kolonisasie deur bioverpulpingsfungi bepaal kon word. Hoë temperature en houtvog wat in sommige areas van die houthope waargeneem is, het laat blyk dat gedeeltes van die hope ongeskik sal wees vir kolonisasie deur mesofiele fungi. Dit sou dus nodig wees om bestuurspraktyke toe te pas om 'n geskikte omgewing vir bioverpulping te handhaaf. Probleme IS ondervind met swak kolonisasie van varsgekapte sagtehoutskerfies deur bioverpulpingsfungi. Die invloed van kontaminerende mikrobes en inhiberende verbindings in hout is daarom ondersoek. Dit is gevind dat inhibisie van bioverpulpingsfungi deur a-pineen en deur kontaminerende mikrobes beide baie belangrik is. Die inhibisie deur mikrobe sowel as vlugtige bestanddele is verlig deur die houtskerfies vir 'n kort periode met stoom te behandel. Stoom vir tien minute by atmosferiese druk kan 'n ekonomiese oplossing wees om kolonisasie van bioverpulpingsfungi te verbeter. Alternatiewelik kan isolate vir bioverpulping met goeie kompeterende vermoë en verdraagsaamheid vir monoterpene geselekteer word. Pinus patula-skerfies is met 'n geselekteerde isolaat van Stereum hirsutum behandel om die optimale toestande vir die kraft-verpulping van fungusbehandelde hout te bepaal en 'n ekonomiese evaluasie van die bioverpulpingsproses te doen. Skerfies is op 'n klein skaalonder verskillende toestande verpulp en die lignien inhoud, opbrengs en viskositeit van die pulp asook alkali-verbruik bepaal. Die data is gebruik om modelle te ontwikkel vir biokraft-verpulping. Die studie het getoon dat die kappagetal of verpulpingstyd deur bioverpulping verminder kan word. Verlies aan pulpopbrengs was relatief laag waar pulp met lae kappagetalle geproduseer is. Die verhoogde alkali-verbruik was egter 'n belangrike faktor by die ekonomiese evaluasie. | af |
| dc.description.sponsorship | Sappi Ltd | en_ZA |
| dc.description.sponsorship | CSIR | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11660/6358 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Basidiomycetes | en_ZA |
| dc.subject | Biodiversity | en_ZA |
| dc.subject | Biopulping | en_ZA |
| dc.subject | Biotechnology | en_ZA |
| dc.subject | Fungi | en_ZA |
| dc.subject | Inhibition | en_ZA |
| dc.subject | Kraft | en_ZA |
| dc.subject | Pulping | en_ZA |
| dc.subject | White-rot | en_ZA |
| dc.subject | Wood | en_ZA |
| dc.subject | Forests and forestry | en_ZA |
| dc.subject | Forest products -- Biotechnology | en_ZA |
| dc.subject | Fungi -- Biotechnology | en_ZA |
| dc.subject | Fungi -- Industrial applications | en_ZA |
| dc.subject | Thesis (Ph.D. (Microbiology and Biochemistry))--University of the Free State, 1999 | en_ZA |
| dc.title | Utilization of wood-decay fungi for biokraft pulping of softwood | en_ZA |
| dc.type | Thesis | en_ZA |