The aim of this work is to contribute to the process development of the ECF light bleaching sequence Q(OP)D(PO) by providing a better understanding of the bleaching of softwood kraft pulp. There are few published studies on this type of sequence, and more knowledge is needed on how to reduce environmental impact, improve cost-effectiveness and ensure a high pulp quality. Firstly, this research showed that using a pH buffer to stabilize the pH at a near-neutral level during bleaching with chlorine dioxide can lower the formation of adsorbable organically bound halogens (AOX) without altering the bleaching efficiency. A near-neutral pH decreases the formation of strongly chlorinating species so that the AOX content in the bleaching effluents is reduced by up to 30%. The increased pH in the near-neutral pH D stage compared with the reference lowered the chlorine dioxide consumption, resulting in a higher kappa number and viscosity. A lower degradation of hexenuronic acid correlated well with a lower AOX content in the effluents, affirming earlier theories that hexenuronic acid has an important impact on AOX formation. Secondly, this research aimed at studying bleachability in (OO)Q(OP)D(PO). The bleachability was defined as delignifying and brightness gain bleachability, which is suited to ECF light bleaching sequences. The delignifying and brightness gain bleachability were used to evaluate the stages in (OO)Q(OP)D(PO) in regard to the unbleached kappa number. When comparing different stages, it is possible to distinguish the bleaching efficiency in each stage. For this ECF light sequence, the bleachability depends on the purpose of the stage. It was found that in the stages that are mainly delignifying (OO and D), a higher unbleached kappa number is beneficial for the delignifying bleachability, although the brightness gain is not improved. However, in the stages that are mainly brightness increasing (OP and PO), the brightness gain bleachability is improved by a lower unbleached kappa number. Thirdly, the bleaching of the pulp samples in this study with the ECF light sequence was most effective with a kappa number around 32 after cooking. Although an even higher kappa number resulted in a higher yield after cooking, it seemed that this bleaching sequence cannot preserve the yield gain. Kappa number 32 also gave the best results in regard to brightness ceiling and viscosity. On the other hand, kappa number 27 was the most favourable with regard to yellowing and chemical charge. / <p>Examinator: Helena Håkansson, lektor, Karlstads universitet</p>

Chemical components in wood contain multiple anionic groups, including carboxyl groups and hydroxyl groups. During kraft cooking and bleaching, such structures are also formed, degraded or modified by the action of reactions both deliberate and unwanted. It has previously been found by Laine that anionic groups with pKa values of 3.3 and 5.5 can explain the observed anionic charge on chemical fibres, corresponding to carboxylic acids on hemicelluloses as well as oxidized lignin structures, respectively. It has further been found that most of the fibre charge can be accounted for through the contribution from methylglucuronic acids as well as hexenuronic acids. This study aimed to provide additional information regarding the charge component unaffiliated with either of the aforementioned uronic acids by studying kraft pulps procured from an industrial kraft mill corresponding to unit operations through a fibreline using the ODHot(EOP)D1D2 bleaching sequence. Each sample had its total charge determined by means of conductometric titration, its content of methylglucuronic acid determined by means of methanolysis followed by GC, and its content of hexenuronic acids determined by means of the HUT-method for the determination of hexenuronic acids, followed by either UV absorbance measurements or calculations based on the reduction in kappa number during the selective acid hydrolysis. The lignin content was determined by means of kappa number analysis as well as by calculations based on the kappa number after selective acid hydrolysis, which was assumed to be characteristic of the kappa number addition from the lignin content of the samples. The hexenuronic acid content was successfully determined according to the HUT-method. A difference in content was observed when results for the unbleached and oxygen delignified samples that was obtained from UV measurements were compared with the observed difference in kappa number prior and after selective acid hydrolysis for said samples. In both cases, the results based on the difference in kappa number was higher. No correlation between remaining charge and lignin content could be made. It was instead observed that individual bleaching steps had binary effects on each of the analysed components of the fibre charge. A significant increase in charge unaffiliated with methylglucuronic acid or hexenuronic acid was observed during the EOP step, indicating an oxidation of chemical structures in the pulp: this effect could not be correlated to lignin content. / Kemisk massa kan ses som ett kompositmaterial bestående av cellulosa, hemicellulosa och lignin. Dessa beståndsdelar, liksom separata lågmolekylära föreningar, innehåller anjoniska kemiska grupper som bidrar till att ge träfibrer en anjonisk laddning. Ytterligare sådana grupper kan bildas under reaktioner vid kokning och blekning, tillika kan sådana grupper modifieras eller brytas ner. Laine har tidigare visat att fiberladdningen kan förklaras genom två skilda kategorier av kemiska grupper med pKa värden på 3,3 samt 5,5, vilka kan kopplas till karboxylsyragrupper på hemicellulosor respektive till lignin. Man har därtill funnit att stora delar av fiberladdningen kan förklaras genom tillskott från de två uronsyrorna metylglukuronsyra och hexenuronsyra. Denna studie syftar till att undersöka det laddningstillskott som inte kan länkas till någon av dessa två uronsyror. Detta har gjorts genom att studera kemiska massor från industrin, tagna från de olika stegen i en bleksekvens av typen ODHot(EOP)D1D2. Massornas totalladdning mättes medelst konduktometrisk titrering, emedan metylglukuronsyrahalten mättes via methanolysis följt av GC och hexenuronsyrahalten mättes via selektiv syrahydrolys per HUT-metoden följt av UV-karakterisering respektive beräkningar baserade på differensen i kappa tal före och efter sagda hydrolys. Ligninhalten i samtliga prov mättes via kappatalsmätningar samt genom beräkningar baserade på kappatalet efter selektiv syrahydrolys, vilket anses vara kappatalsbidraget från ligninföreningarna. Hexenuronsyrahalterna uppmätta medelst UV-karakterisering respektive kappatalsdifferens jämfördes mot varandra och fanns ge olika resultat för de oblekta och syrgasdelignifierade massorna. I bägge fallen gav mätningen baserade på kappatalsdifferens högre utslag. Ingen korrelation mellan kvarvarande laddning - totalladdning minus tillskottet från uronsyrorna - och ligninhalt kunde observeras. Istället observerades binära effekter för varje uppmätt komponent under vardera blekningssteg. Under EOP-steget observerades ett tillskott till den kvarvarande laddningen, vilket skulle kunna förklaras genom oxidation av trästrukturer. Dock kan ej heller detta relateras till ligninhalten i proverna.

The aim with this project was to investigate how the amount and composition of resins varied during the process producing bleached birch pulp at the mill SCA Packaging Munksund. A literature study about how the resin removal can be improved has also been included. Problems with resins in the process are common at pulp and paper mills, especially when birch is used as a raw material. The resin can cause deposits on the equipment leading to process stops, but also lowered mechanical properties and spots on the paper products. The addition of tall oil to the digester is one way of improving the removal of resins, seasoning of wood, and a good debarking are other ones. Also the different washing and bleaching steps can affect the amount of resin remaining in the pulp. In this study pulp samples from eight different positions in the process were analyzed. To extract the samples a Soxtec device was used. Results showed that the most effective resin removal happened during the washing in their first washing step after the digester, a DD-washer. Here 77 % of the resin was removed, of totally 88 % during the whole process. Another step which was effective was the final washing step, the PO-press. About 36 % of the remaining resins in the pulp which entered the PO-press were washed out here. The extracts were analyzed with GC-FID and GC-MS to identify and quantify the substances, and determine how the composition varied over the manufacturing process. Twelve different compounds were identified, and the birch bark resin, betulinol, turned out to be the hardest component to remove. Over all, the sterols and triterpenols were hard to deresinate, while the removal of resin acids, fatty acids, and fatty alcohols was more effective. The PO-reactors showed a positive effect on the fragmentation of components consisting of long carbon chains and double bonds, like squalene and betulaprenols. / Målet med projektet var att utreda hur mängden och sammansättningen av hartser varierade i den blekta björkmassan under tillverkningsprocessen på pappersbruket SCA Packaging Munksund. Att göra en litteraturstudie för att ta reda på vilka metoder som kan användas för att förbättra avhartsningen var en annan del av målet. Att pappers- och massatillverkare har problem med hartser är vanligt, speciellt när björkved används som råmaterial. Hartserna kan orsaka beläggningar på utrustningen som i sin tur kan leda till processtop, men även prickar och försämrade mekaniska egenskaper hos pappersprodukten. Att tillsätta tallolja till kokaren är en vanlig metod som används för att förbättra hartsreningen, att lagra träet innan koket, och lägga fokus på att förbättra barkningen är andra metoder. Även de olika blek- och tvättstegen som används under tillverkningen av massan kan påverka hartshalten. I denna studie analyserades massaprover från åtta olika positioner i processen. En Soxtec-utrustning användes för att extrahera massaproverna. Resultatet visade att den mest effektiva avhartsningen sker under tvätten i det första tvättsteget efter kokaren, DD-filtret. Här tvättades 77 % av hartserna ut, och totalt minskade mängden hartser med 88 % under hela processen. PO-pressen var ett annat tvättsteg som var effektivt ur avhartsningssynpunkt. Här togs 36 % av den kvarvarande mängden hartser bort från massan. Extrakten som erhållits från extraktionen analyserades vidare med GC-MS och GC-FID. Dessa metoder användes för att identifiera och kvantifiera extraktivämnena, och bestämma hur sammansättningen varierade under tillverkningsprocessen. Tolv olika ämnen identifierades och den substans som visade sig vara svårast att tvätta bort var björkbark hartset, betulinol. Stort sett så var steroler och triterpenoler svårast att bli av med, medans avhartsingen av hartssyror, fettsyror och fettalkoholer var mer effektiv. Det visade sig även att PO-reaktorerna hade en sönderdelande effekt på substanser såsom squalen och betulaprenoler, dessa består av långa kolkedjor med många dubbelbindningar mellan kolatomerna.

Syftet med detta examensarbete var att öka reaktiviteten hos förhydrolyserad kraftmassa genom att använda tidigare förhydrolysat och svavelsyra under förhydrolysen. Först bestämdes den kemiska sammansättningen av två olika vedråvaror (Acacia crassicarpa och Eucalyptushybrider) för att observera och korrelera med förhydrolysprocessen. Därefter studerades effekten av att för förhydrolyskraftkokning använda vatten, förhydrolysat och svavelsyra med olika koncentration under förhydrolysen vilket korrelerades med avlägsnandet av pentosan, utbyte, viskositet, kappanummer och ljushet. Därefter valdes en av vardera syrabaserad förhydrolyskraftmassa att blekas helt till dissolvingmassa för bestämning av Fock-reaktivitet, vilket jämfördes mot den vattenbaserade förhydrolysen som referens. Den slutliga kvaliteten på de olika förhydrolyskraftmassorna studerades också. Detta examensarbete visade att användandet av förhydrolysat och svavelsyra kan ge högre Fock-reaktivitet jämfört med vatten under liknande processförhållanden. Däremot gav syrabaserad förhydrolyskraftmassa lägre utbyte än vattenbaserad förhydrolyskraftmassa. Syrabaserad förhydrolyskraftkokning gav även lägre pentosanhalt, lägre halt extraktivämnen och lägre viskositetsvärden. Förhydrolysatbaserad förhydrolyskraftmassa hade värden mellan de som uppvisades av vattenbaserade- och svavelsyrabaserade förhydrolyskraftmassor. Dessutom hade förhydrolyskraftmassor från Eucalyptushybrider högre Fock-reaktivitet, lägre pentosanhalt, lägre halt extraktivämnen och högre viskositet än förhydrolyskraftmassor från Acacia crassicarpa. / The worldwide demand for dissolving pulp has been increasing significantly in Asia which is majorly produced from prehydrolysis kraft pulping and most of the prehydrolysis kraft pulp are consumed in viscose rayon production. Thus, it is interesting to have research in the process of prehydrolysis kraft pulping to make it a cleaner and more sustainable production. One of the most important qualities of prehydrolysis kraft pulp in viscose rayon is reactivity, which can lead to less chemical consumption and lower production cost. The aim of this research project is to increase the reactivity of prehydrolysis kraft pulp by using prehydrolysate and sulfuric acid during prehydrolysis cooking. Firstly, the wood chemical composition of two different hardwood species (Acacia crassicarpa and Eucalyptus hybrids) were determined and correlated with the prehydrolysis kraft pulping process. Secondly, prehydrolysis kraft cooking using water, prehydrolysate, and sulfuric acid with different concentration during prehydrolysis were studied and correlated with pentosan removal, yield, viscosity, kappa number, and brightness. Later, one of each acid based prehydrolysis kraft pulping were chosen to be proceed to fully bleached dissolving pulp for determining Fock reactivity which was compared to water prehydrolysis kraft pulping as the reference. The final quality of different prehydrolysis kraft pulps were also studied. From this research project, it showed that prehydrolysate and sulfuric acid prehydrolysis kraft pulp improved the Fock reactivity as compared to water prehydrolysis in similar pulping condition. However, acid based prehydrolysis kraft pulping gave lower yield than water prehydrolysis kraft pulping. Acid based prehydrolysis kraft cooking provided lower pentosan and extractive content, but lower viscosity values. Meanwhile, the prehydrolysate kraft pulp had the intermediate values between water and sulfuric acid prehydrolysis kraft pulping. In addition, Eucalyptus hybrids prehydrolysis kraft pulping had higher Fock reactivity, lower pentosan content, lower extractives, and higher viscosity than Acacia crassicarpa. To conclude, the more acidic prehydrolysis increased Fock reactivity with lower pulp yield, pentosan, extractive and viscosity.

The kraft pulping process is the most dominant pulping process consisting of 90% of the chemical virgin pulp production in the world. This process is extensive, especially considering the large chemical recycling, and improvements are constantly ongoing [1]. In 1966, G.H. Tomlinson II published a patent in where a white liquor of 100% sulphidity was used, i.e. only sodium sulphide (Na2S) as a cooking chemical and not sodium hydroxide (NaOH). A higher sulphidity gives an improved delignification and a stronger pulp with a higher yield. In addition, when NaOH is not used in the process, the causticizing plant can be eliminated. According to Tomlinson II, this would mean lower investment and operating costs.  The smelt from the recovery boiler undergoes leaching or evaporating to separate the sodium carbonate (Na2CO3) and Na2S. Na2CO3 recirculates to the black liquor to reduce the sulphur/sodium ratio, which is necessary for the function of the recovery boiler. A sufficiently high proportion of recirculated Na2CO3 is used to ensure that no SO2-emissions occur from the recovery boiler [2]. The purpose of this thesis is to investigate different cases of high sulphidity processes through heat and mass balances and compare it with a reference case of kraft pulp, in order to potentially find a more efficient process. The high sulphidity cases vary with e.g. dry solids content, effective alkali charge and the amount of recirculated Na2CO3. Also, a combination between the conventional kraft pulping process and high sulphidity process will be investigated. Tools for these calculations are given from AFRY and is done in excel. The focus is on the recovery boiler, since it is the most critical aspect in the process, but overall flow charts will also be made.  It turns out that the amount of recirculated Na2CO3 is one of the major factors that determine the outcome of the results. An increased amount of Na2CO3, which contains inert carbon, leads to a lower heating load in the recovery boiler, resulting in too low temperatures. For the high sulphidity process to be feasible, a lower effective alkali charge is required in the digester to reduce the amount of chemicals in the process. This can be achieved through a pre-impregnation step in the digester. All high sulphidity cases also resulted in a decrease in CAPEX and OPEX compared to the reference case. The most interesting result is a combination between the high sulphidity and kraft pulping process, as the results was comparable with the reference case, but at the same time containing advantages of the high sulphidity process. / Kraftmassaprocessen är den dominerade massaframställningen bestående av 90% av världens kemiska jungfrumassa. Denna process är omfattande och förbättringar pågår ständigt, särskilt med tanke på den stora kemikalieåtervinningen [1]. 1966 publicerade G.H. Tomlinson II ett patent där en vitlut av 100% sulfiditet användes, alltså endast natriumsulfid (Na2S) och inte natriumhydroxid (NaOH) som kokkemikalie. En högre sulfiditet ger en förbättrad delignifiering och därmed en starkare massa med ett högre utbyte. När NaOH inte används i kokeriet kan dessutom kaustiseringen elimineras. Det skulle, enligt Tomlinson II, innebära lägre investerings- och driftskostnader.  Smältan som kommer ut från sodapannan genomgår en laknings- eller indunstningsprocess för att separera ut natriumkarbonatet (Na2CO3) och Na2S. Na2CO3 återcirkulerar till svartluten innan sodapannan för att på så sätt minska på svavel till natriumkvoten, vilket är nödvändigt för sodapannans funktion. En tillräckligt hög andel av Na2CO3 återcirkuleras för att inga SO2-emissioner ska förekomma [2]. Syftet med denna rapport är därför att undersöka olika fall av högsulfiditetsprocesser genom värme och massbalanser och jämföra med ett referensfall av kraftmassa, för att i slutändan undersöka en potentiellt mer effektiv process. Fallen varierar med torrhalt på svartluten, effektiv alkali laddning, och mängden återcirkulerad Na2CO3. Ett kombinerat fall mellan den konventionella kraftmassa- och högsulfiditetsprocessen kommer även att undersökas. Verktyg för dessa beräkningsbalanser fås via AFRY och används i Excel. Fokuset ligger på sodapannan då denna del av processen är avgörande för processens genomförbarhet.  Övergripande flödesscheman kommer även att göras för de olika fallen.  Det ska visa sig att mängden återcirkulerad Na2CO3 är en av de större faktorerna till förändringar i resultatet. En ökad mängd Na2CO3, som innehåller inert kol, ger en lägre värmebelastning i sodapannan, och därmed för låga temperaturer i pannan. För att högsulfiditetsprocessen ska kunna vara genomförbar krävs en lägre effektiv alkali laddning i kokeriet för att minska på mängden kemikalier i processen, detta kan göras via ett förimpregneringssteg i kokeriet. Alla högsulfiditetsfall gav även en minskning i CAPEX och OPEX jämfört med referensfallet. Mest intressant resultat gavs av en kombination mellan högsulfiditet och kraftmassaprocess, då den mest efterliknade referensfallet, men samtidigt innehåller fördelar av högsulfiditetsfallet.

La contamination des surfaces par des bactéries et l’émergence de souches résistantes aux antimicrobiens sont des problèmes très préoccupants dans différents domaines tel que les domaines hospitalier et alimentaire. Cette contamination commence par l’adhésion de bactéries pathogènes sur une surface jusqu’à la formation de biofilms. Ces derniers contribuent à l’émergence de résistances de certaines souches bactériennes aux traitements conventionnels. Pour répondre à ces problèmes de contamination des surfaces, ces travaux de thèse portent sur le développement de nouveaux matériaux antibactériens à base de fibres de pâte à papier. Nous nous sommes intéressés, dans une première partie, à l’élaboration d’un papier antibactérien par le greffage, via un lien triazine, de deux composés d’huiles essentielles, le thymol et le carvacrol, connus pour leurs activités antibactériennes. L’évaluation microbiologique des matériaux élaborés, sur les deux souches bactériennes testées, E.coli et S.aureus, a montré un effet bactériostatique. Ces matériaux bloquent donc la croissance bactérienne empêchant ainsi la formation des biofilms. Une synergie entre le thymol et le carvacrol lorsqu’ils sont greffés sur les fibres de pâte à papier a également été montré. Dans une deuxième partie, notre étude s’est focalisée sur l’élaboration d’un papier antibactérien qui n’acquière son activité qu’après greffage et formation du motif actif « aryl-1,2,3-triazole ». Le greffage est réalisé par une réaction de « Click Chemistry », la cycloaddition de Huisguen catalysée par le cuivre I. Les tests antibactériens révèlent l’importance du substituant de l’aryle, l’influence du temps de contact et la pertinence d’utiliser des mélanges de matériaux. L’activité antibactérienne observée sur les fibres de la pâte thermomécanique est meilleure dans les deux parties. Les différents résultats obtenus sont décrits dans ce manuscrit. / The contamination of surfaces by bacteria and the emergence of antimicrobial resistant strains are very worrying problems in different areas such as hospital and food. This contamination begins with the adhesion of pathogenic bacteria on a surface until the formation of biofilms. These biofilms contribute to the emergence of resistances of certain bacterial strains to conventional treatments. To answer these problems of surface contamination, this thesis work focuses on the development of new antibacterial materials based on pulp fibers. In the first part, we focused on the development of an antibacterial paper by grafting, via triazine link, two essential oil compounds, thymol and carvacrol, known for their antibacterial activities. The microbiological evaluation of the developed materials against the two bacterial strains tested, E. coli and S. aureus, showed a bacteriostatic effect. These materials block the bacterial growth thus preventing the biofilms formation. Synergy between thymol and carvacrol grafted onto paper has also been shown. In a second part, our study focused on the development of an antibacterial paper that acquires its activity only after the grafting and formation of "aryl-1,2,3-triazole", the active motif. The grafting is carried out by a reaction of "Click Chemistry", the copper (I)-catalyzed Azide Alkyne Cycloaddition. The antibacterial tests reveal the importance of the aryl substituent, the influence of the contact time and the relevance of using mixtures of materials. The antibacterial activity observed on the thermomechanical pulp fibers is better in both parts. The different results obtained are described in this manuscript.

QC 20120530

Made available in DSpace on 2015-03-26T14:01:03Z (GMT). No. of bitstreams: 1 texto completo.pdf: 684853 bytes, checksum: 5aab9bbea25fa23492af8fc69a587a05 (MD5) Previous issue date: 2010-06-10 / Efforts to develop new sources of energy from renewable resources has greatly increased. Great efforts have been made in pulp mills to incorporate in foreseeable future biorefineries operations to simultaneously achieve production of pulp and biofuels aiming total or partial substitution of fossil fuels. The objective of this study was to evaluate the feasibility of using LignoBoost technology in a modern eucalyptus pulp mill and its impact in the mill energy matrix and greenhouse gases emissions. / Tem aumentado grandemente os esforços para desenvolvimento de novas fontes de energia proveniente de recursos renováveis. Grandes esforços têm sido realizados, em fábricas de celulose, para que, num futuro próximo, possam ser incorporadas nestas empresas operações de biorefinarias, visando produção simultânea de celulose e biocombustíveis para substituição total ou parcial de combustíveis fósseis. O objetivo deste trabalho foi avaliar a viabilidade do uso da tecnologia LignoBoost em uma moderna fábrica de celulose kraft de eucalipto e seus impactos na matriz energética e na emissão de gases de efeito estufa.

Made available in DSpace on 2015-03-26T14:01:04Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2018234 bytes, checksum: 43a78e55f7947551d68ec57851bddcc5 (MD5) Previous issue date: 2010-07-08 / In this study, data collected on an industrial scale for some years, underwent modeling using generalized additive models (GAM) and artificial neural networks (ANN) as tools to evaluate the influence of some variables, timber and process on production and digester alkali charge. Generalized additive models were fitted using the software R (R Development Core Team, 2010), through the library "mgcv" (Wood, 2006), specific settings for generalized additive models. Significance tests were applied for each model set. In order to supplement the data were analyzed using artificial neural networks.One hundred RNA were adjusted to relate to production and the digester alkali charge, and variables such as wood density, age, precipitation, dry content of wood chips, bulk density of chips, the wood basic density, pulp viscosity and kappa. In this step we employed the software Statistica (Statsoft, Inc., 2007). The results show that the Generalized Additive Model (GAM) is a good choice to represent the phenomena of the pulp industry, where the variables are highly variable and there is strict control, unlike what happens on data from experimental designs. Should the use of RNA to estimate the output from the digester alkali charge and also proved a useful tool, since the correlations between actual and estimated data were above 88% and 60% respectively. Several variables associated with the raw material and the pulping process that were studied showed similar behavior and / or equal to what the majority of experimental studies have found. / No presente trabalho, dados observados em escala industrial, durante alguns anos, foram submetidos à modelagem empregando modelos aditivos generalizados (GAM) e redes neurais artificiais (RNA), como ferramentas para avaliar a influência de algumas variáveis, da madeira e do processo, sobre a produção do digestor e carga alcalina. Os modelos aditivos generalizados foram ajustados utilizando o software R (R DEVELOPMENT CORE TEAM, 2010), através da biblioteca &#8220;mgcv&#8221; (WOOD, 2006), específica para ajustes de modelos aditivos generalizados. Foram aplicados testes de significância para cada modelo ajustado. De forma complementar os dados foram analisados por meio de redes neurais artificiais. Foram ajustadas 100 RNA para relacionar a produção do digestor e a carga alcalina, com as variáveis: densidade da madeira, idade, precipitação, teor seco dos cavacos, densidade aparente dos cavacos, densidade básica dos cavacos, viscosidade da polpa e kappa. Nesta etapa do trabalho foi empregado o software Statistica (Statsoft, INC, 2007). Os resultados mostram que o Modelo Aditivo Generalizado (MAG) constitui uma boa opção para representar os fenômenos da indústria de celulose, em que as variáveis apresentam alta variabilidade e não há um rigoroso controle, diferentemente do que ocorre em dados provenientes de delineamentos experimentais. No caso do uso de RNA para estimar a produção do digestor e para carga alcalina também mostrou ser uma boa ferramenta, visto que as correlações entre os dados reais e estimados ficaram acima de 88% e 60%, respectivamente. Várias variáveis associadas com a matéria-prima e com o processo de polpação que foram estudadas apresentaram comportamento semelhante e/ou iguais o que a maioria dos estudos experimentais encontraram.

Xylanases have an important role as biocatalysts in different agroindustrial processes, such as saccharification of plant residues for the production of ethanol and bleaching of wood pulp for the production of pulp. On an industrial scale, these processes may require extreme pH or temperature, which require enzymes compatible with these conditions. Most enzymes available or showing commercial potential is synthesized by fungi or bacteria belonging to a few genera. Evaluation of rare isolation bacteria is an important strategy to expand the diversity of xylanases and their potential in terms of activity, stability and technological application. The aim of this study was to evaluate a collection of common and rare isolation soil bacteria regarding to xylanase activity and characterize the stability conditions of temperature and pH. The analyzed collection consists of 120 isolates with representatives from six phyla that were subjected to screening for xylanase activity in pure cultures and in the extracellular proteic extract (EPE). The ratio between the halos diameters of xylan hydrolysis and in the colonies on solid medium (ratio H:C), incubated at 30 ° C for up to 14 days, was used for the evaluation of cultures as a selection criteria. The effects of different sources of variation in the bacteria isolation stage (original soil, culture medium, solidifying agent, inoculum dilution and plating method and incubation time to colony appearance) and the group of bacterial isolation (rare or common) on the frequency of isolates with high xylanase activity were evaluated based on the ratio H:C. EPEs were obtained in liquid media containing xylan inoculated with the eleven isolates with highest ratios H:C. The extracts were evaluated for the specific xylanase activity at 50 °C for 1 h. Extracts of the three isolates with the highest potential for activity under this condition were evaluated for optimum activity, stability, activity at 60 oC and at pH 4.0, 5.5 and 8.0. Twenty-two isolates (25%), including eight from rare isolation, showed xylanase activity under the conditions evaluated, and found a high variability (> 230%) between these isolates. No isolation factor or rare or common isolation condition were associated with efficiency of xylanase activity in solid medium. High variability in specific xylanase activity in EPEs was also found among isolates (1500%), highlighting two rare isolates (TC119 and TC21), from Alfaproteobacteria class, and one common isolate (TC99), from Ralstoniaceae family. Extracellular xylanases from TC21 and TC119 showed high relative activity at temperatures up to 70 oC and were insensitive to pH in the range 4.0 to 8.0; however, TC99 isolate showed optimum temperature at 40 °C and low stability to temperature and pH. Extracellular xylanases from TC119 showed no cellulolytic activity. Rare isolation soil bacteria show high potential as a source of extracellular xylanases adapted to extreme pH and temperature conditions, which are required in agroindustrial processes. / As xilanases apresentam papel relevante como biocatalisadores de diferentes processos agroindustriais, como a sacarificação de resíduos vegetais para a produção de etanol e o clareamento de polpas de madeira para a produção de celulose. Em escala industrial, estes processos podem requerer pH e, ou, temperatura extremos, os quais demandam enzimas compatíveis com estas condições. A maioria das enzimas disponíveis ou com potencial comercial é sintetizada de fungos ou de bactérias pertencentes a poucos gêneros. A avaliação de bactérias de isolamento raro constitui-se em estratégia importante para ampliar a diversidade de xilanases e suas potencialidades em termos de atividade, estabilidade e aplicação tecnológica. O objetivo deste trabalho foi avaliar uma coleção de bactérias do solo de isolamento comum e raro quanto à atividade de xilanases e caracterizar estas enzimas quanto à estabilidade a condições contrastantes de temperatura e pH. A coleção analisada é composta de 120 isolados com representantes de seis filos e foi submetida à seleção quanto à atividade de xilanases em culturas puras e no extrato proteico extracelular (EPE). Para a avaliação das culturas, utilizou-se como critério de seleção a relação entre os diâmetros de halos de hidrólise de xilana e das colônias em meio sólido (relação H:C), incubado a 30 oC por até 14 dias. Os efeitos de diferentes fontes de variação da fase de isolamento destas bactérias (solo de origem, meio de cultura, agente solidificante, diluição do inóculo e método de plaqueamento e tempo de incubação até surgimento de colônias) e do grupo de isolamento bacteriano (raro ou comum) sobre a frequência de isolados com alta atividade de xilanase foram avaliados com base na relação H:C. EPEs foram obtidos em meios líquidos contendo xilana inoculados com os onze isolados com maiores relações H:C. Os extratos foram avaliados quanto à atividade específica de xilanases a 50 oC, por 1 h. Os extratos dos três isolados com maior potencial de atividade sob esta condição foram avaliados quanto à temperatura ótima de atividade, estabilidade de atividade a 60 oC e a valores de pH 4,0, 5,5 e 8,0. Vinte e dois isolados (25%), incluindo oito de isolamento raro, apresentaram atividade de xilanase nas condições avaliadas, sendo encontrada uma alta variabilidade (>230%) entre estes isolados. Nenhum fator de isolamento ou a condição de isolado raro ou comum foram associadas à eficiência de atividade de xilanases em meio sólido. Alta variabilidade de atividade específica de xilanases nos EPEs também foi encontrada entre os isolados (1500%), com destaque para dois de cultivo raro (TC119 e TC21), da classe Alfaproteobacteria, e um de cultivo comum (TC99), da família Ralstoniaceae. As xilanases extracelulares de TC119 e TC21 apresentaram elevada atividade relativa em temperaturas de até 70 oC e foram pouco sensíveis ao pH na faixa de 4,0 a 8,0; entretanto, as de TC99 apresentaram temperatura ótima de 40 oC, baixa estabilidade a temperatura e pH. Xilanases extracelulares de TC119 não apresentaram atividade celulolítica. Bactérias do solo de isolamento raro apresentam alto potencial como fonte de xilanases extracelulares adaptadas a condições extremas de pH e temperatura requeridas em processos agroindustriais.