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dc.contributor.advisorDu Preez, J. C.
dc.contributor.advisorChristopher, L.
dc.contributor.authorChipeta, Zawadi Arthur
dc.date.accessioned2018-07-31T07:53:20Z
dc.date.available2018-07-31T07:53:20Z
dc.date.issued2005-05
dc.identifier.urihttp://hdl.handle.net/11660/9043
dc.description.abstractEnglish: The application of xylanolytic enzymes in the pulp and paper industry is considered one of the most important new large-scale biotechnological applications of enzymes. Incorporation of these enzymes in the bleaching process has resulted in the decreased use of chlorinebased chemicals as well as the production of less hazardous waste waters. One of the factors limiting the widespread commercial application of xylanases is the cost of production, which may be decreased by the use of lignocellulosic materials as inducer as well as carbon substrate. The main objective of this study was to evaluate spent sulphite liquor (SSL) that had been concentrated five-fold at a South African pulp mill as an alternative inexpensive carbon feedstock for xylanase production by strains of Aspergillus and Gliocladium. These fungal strains were evaluated for xylanase production with SSL, xylan and D-xylose as carbon substrates initially in shake flask cultures. Aspergillus oryzae NRRL 3485 and A. phoenicis ATCC 13157 yielded higher xylanase activities with SSL than with xylan as carbon substrate, although xylan induced a higher xylanase activity per g cell mass. Xylose induced little to no xylanase activity in the fungal strains evaluated. Apart from the sugars in the SSL, the above Aspergillus strains also utilised a non-sugar component in the SSL as additional carbon substrate, as indicated by total organic carbon analysis. The utilisation of the nonsugar component in the SSL resulted in high biomass concentrations which gave high biomass yield coefficients if calculated in terms of only the sugars present in the SSL. Characterisation of the crude xylanase preparations of A. oryzae and A. phoenicis indicated three and two xylanase isozymes with molecular weights of approximately 32, 22, 19 and 25 and 21 kDa, respectively. The A. oryzae xylanase preparation exhibited unusually high pH and temperature optima of 6.5 and 65 °C, respectively, therefore being better suited for biobleaching applications in the pulp and paper industry, whereas the properties of the xylanase preparation from A. phoenicis were typical of fungal xylanases. In bioreactor cultures of A. oryzae using SSL as carbon substrate, the cultivation pH had a significant effect on xylanase production, with pH 7.5 resulting in the highest xylanase activity. The agitation rate in the range of 400 to 800 rpm had no effect on xylanase production by Aspergillus oryzae NRRL 3485. Xylose repression of xylanase production was alleviated in fed-batch culture operating at a constant feed rate of 2.38 g xylose h-1, where a xylanase activity of up to 210 U ml-1 was reached. Xylanase production was further increased up to 260 U ml-1 by increasing the (NH4)2SO4 concentration in the medium. These values rank amongst the highest xylanase activities reported for Aspergillus strains. Pretreatment of the SSL using ultrafiltration and overliming resulted in decreased xylanase activities. Although both pretreatment procedures resulted in the removal of compounds inhibitory to microbial growth, they may have also resulted in the removal of the inducing compound/s, hence the low xylanase activities obtained with the pretreated SSL. SSL, a waste water of the pulp and paper industry, therefore could serve both as carbon substrate and inducer for xylanase production, yielding high xylanase activities as well as biomass concentrations. Furthermore, these xylanase preparations were cellulase-free and in laboratory trials with hardwood pulp their application decreased the usage of chlorine bleaching chemicals by 20 to 30% without sacrificing brightness, thus demonstrating their potential for application as biobleaching agents in the pulp and paper industry.en_ZA
dc.description.abstractAfrikaans: Die gebruik van xilanolitiese ensieme in die pulp- en papiernywerheid word as een van die mees belangrike nuwe grootskaalse biotegnologiese toepassings van ensieme beskou. Die inkorporering van hierdie ensieme in die verbleikingsproses het die verminderde gebruik van chloorgebaseerde chemikalieë asook die produksie van minder-gevaarlike afvalwater tot gevolg gehad. Een van die faktore wat die algemene kommersiële toepassing van xilanases beperk, is die produksiekoste, wat verlaag kan word deur die gebruik van lignosellulosestowwe as induseerder sowel as koolstofsubstraat. Die hoofdoel van hierdie studie was om die sulfietafvalwater (SAW) wat vyfvoudig deur 'n Suid-Afrikaanse pulpmeule gekonsentreer is, as 'n alternatiewe goedkoop koolstofbron vir xilanaseproduksie deur stamme van Aspergillus en Gliocladium te evalueer. Hierdie fungusstamme is ten opsigte van xilanaseproduksie met SAW, xilaan en D-xilose as koolstofsubstrate aanvanklik in skudfleskulture geëvalueer. Aspergillus oryzae NRRL 3485 en A. phoenicis ATCC 13157 het hoër xilanase-aktiwiteite met SAW as met xilaan as koolstofsubstraat gelewer, alhoewel xilaan 'n hoër xilanase-aktiwiteit per g selmassa geïnduseer het. Xilose het min tot geen xilanase-aktiwiteit in die fungusstamme wat geëvalueer is, geïnduseer. Buiten die suikers in die SAW het die bg. Aspergillus stamme ook 'n nie-suiker komponent in die SAW as addisionele koolstofsubstraat benut, soos wat deur totale organiese koolstofanalise aangedui is. Die benutting van die nie-suiker komponent van die SAW het hoë biomassa-konsentrasies tot gevolg gehad, wat hoë biomassaopbrengskoëffisiente gegee het indien dit in terme van slegs die suikers wat in die SAW teenwoordig was, bereken is. Karakterisering van die onsuiwer xilanase preparate van oryzae and A. phoenicis het drie en twee xilanase-isosieme met molekulêrgewigte van ongeveer 32, 22, 19 en 25 en 21 kDa, onderskeidelik, aangedui. Die A. oryzae xylanase preparaat het ongewoon hoë pH- en temperatuuroptima van onderskeidelik 6.5 en 65 °C getoon, en was derhalwe beter geskik vir bioverbleikingstoepassings in die pulp- en papiernywerheid, terwyl die eienskappe van die xilanase preparaat van A. phoenicis tiperend van fungus-xilanases was. In bioreaktorkulture van A. oryzae met SAW as koolstofsubstraat het die kwekings-pH 'n beduidende effek op xilanaseproduksie gehad, en pH 7.5 het die hoogste xilanase-aktiwiteit tot gevolg gehad. Die roersnelheid in die bestek van 400 tot 800 opm het geen effek op xilanaseproduksie deur Aspergillus oryzae NRRL 3485 gehad nie. Xilose-repressie van xilanaseproduksie is verminder deur gebruik te maak van 'n gevoerde lotkultuur ("fed-batch culture") wat teen 'n konstante voersnelheid van 2.38 g xylose h-1 bedryf is, waarin 'n xilanase-aktiwiteit van tot 210 E ml-1 bereik is. Xylanase-produksie is nog verder tot 260 E ml-1 verhoog deur die (NH4)2SO4 konsentrasie in die medium te vermeerder. Hierdie waardes is van die hoogste xilanase-waardes wat nog vir Aspergillus stamme gerapporteer is. Voorafbehandelilng van die SAW deur ultrafiltrasie en oorneutralisasie het verlaagde xilanase-aktiwiteite tot gevolg gehad. Alhoewel albei vooraf-behandelingsprosedures die verwydering van verbindings wat inhiberend vir mikrobiese groei was, tot gevolg gehad het, het hulle dalk ook die verwydering van die induserende verbinding/s meegebring; derhalwe die lae xilanase-aktiwiteite wat met die voorafbehandelde SAW verkry is. SAW, 'n afvalwater van die pulp- en papiernywerheid, kon dus as beide 'n koolstofsubstraat en induseerder vir xilanaseproduksie dien, wat hoë xilanase-aktiwiteite asook biomassakonsentrasies gelewer het. Verder, die xilanase preparate was sellulase-vry en in laboratoriumproewe met hardehoutpulp het hul aanwending die verbruik van chloor-verbleikingschemikalieë met 20 tot 30% verminder sonder om helderheid te benadeel, wat dus hul potensiaal vir aanwending as bioverbleikingsagense in die pulp- en papiernywerheid gedemonstreer het.en_ZA
dc.description.sponsorshipNational Research Foundation (NRF)en_ZA
dc.description.sponsorshipWater Research Commissionen_ZA
dc.description.sponsorshipSappi Saiccoren_ZA
dc.description.sponsorshipMicrobial, Biochemical and Food Biotechnology, University of the Free Stateen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectSpent sulphite liquoren_ZA
dc.subjectPulp and paperen_ZA
dc.subjectXylanaseen_ZA
dc.subjectXylanen_ZA
dc.subjectXyloseen_ZA
dc.subjectFungusen_ZA
dc.subjectAspergillusen_ZA
dc.subjectBiobleachingen_ZA
dc.subjectFungal enzymesen_ZA
dc.subjectSulfite waste liquoren_ZA
dc.subjectWood-pulp industry -- Waste disposalen_ZA
dc.subjectThesis (Ph.D. (Microbial, Biochemical and Food Biotechnology))--University of the Free State, 2005en_ZA
dc.titleFungal utilisation of pulp mill waste water for xylanase productionen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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