Xylan is one of the major hemicelluloses present in plant cell wall matrix, where it is closely associated with other cell wall components, cellulose and lignin. Xylan has enormous potential as a renewable biopolymer and recently, research in the direction of isolation and utilization of xylan is gaining lot of research attention. Extraction of xylan from the plant cell walls involves the hydrolysis of xylan and its transfer from the plant cell wall matrix to the hydrolyzing media. Current process of extraction involves prolonged heating of the biomass with the hydrolysis media at high temperature and/or pressure that leads to molecular degradation of xylan and limits its high potential polymeric applications. In this research, microwave assisted alkaline extraction of polymeric xylan from birch wood is investigated as an alternative to the time intensive conventional extraction. The hypothesis to be tested is that the microwave’s selective heating ability leads to the generation of hot spots through its interaction with the alkali present in the fibers and the resulting "explosion effect" loosen the recalcitrant fiber structure network thereby facilitating the hydrolysis of xylan and its dissolution before undergoing significant degradation. Effect of microwave extraction on the yield of xylan and wood solubilization, physico-chemical properties of wood fibers and of isolated xylan were investigated in comparison with conventional extraction. Low power input microwave (110 W) alkaline extraction was found to be an efficient alternative to the conventional extraction. FTIR and chemical composition of wood fibers after extraction demonstrated an increased removal of xylan from the wood fibre using microwave extraction. SEM, X-ray microtomography, and X-ray crystallinity studies of wood fibers demonstrated a porous and loosened fibre structure after microwave extraction confirming the hypothesis. Molecular weight of the isolated xylan using microwave extraction was found to be higher compared to the xylan isolated using conventional extraction indicating less molecular degradation. About 75% of xylan present in birch wood could be extracted using a low power input microwave heating under optimized extraction conditions of 8wt% NaOH solution, 1:8 (g:mL) solid to liquid ratio, and 25 minutes of extraction time.

Orientador: Francisco Maugeri Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-10T15:34:14Z (GMT). No. of bitstreams: 1 Motta_FelipeBastos_M.pdf: 972824 bytes, checksum: a462e688ab46d2def7974c05146d274b (MD5) Previous issue date: 2008 / Resumo: A endo-1,4-ß-xilanase (E.C. 3.2.1.8), comumente chamada de xilanase, possui grande aplicação em diferentes tipos de indústrias tais como a de ração animal, alimentos, têxteis, de papel, de produção de etanol a partir de biomassa, entre outras. Isso se deve ao fato de que esta enzima atua na hidrólise da xilana, o segundo mais abundante polissacarídeo encontrado na natureza, que está presente ligado a hemicelulose da parece celular de plantas. O objetivo deste trabalho foi selecionar, através do método de screening em placas de Petri, e avaliar a atividade enzimática de leveduras silvestres isoladas de diversas regiões do Brasil (Mata Atlântica, Floresta Amazônica, Cerrado e Pantanal) quanto à produção de xilanase. Para o screening em placas, utilizou-se um meio de cultura no qual a única fonte de carbono era a xilana para induzir a produção da enzima. De um total de 349 microrganismos analisados, foram obtidas 84 cepas produtoras, porém somente 37 possuíam um índice de relação enzimática (diâmetro do halo descolorido / diâmetro da colônia) maior que 2,5. Em função deste resultado prosseguiu-se com a seleção dos melhores microrganismos para a produção da enzima em meio líquido. Após observações preliminares apenas 9 cepas obtiveram um crescimento satisfatório em meio líquido a 30ºC e 150 rpm. Estes foram avaliados em dois meios de culturas diferentes em relação à atividade enzimática do caldo enzimático à 50ºC por 5 min em shaker. Dentre estes, os microrganismos AAD5 e AY10 se destacaram por apresentarem a atividade enzimática em torno de 2 µmol/mL.min . Posteriormente, foi realizada a caracterização das enzimas produzidas, sendo que a proveniente do microrganismo AAD5 possui condições ótimas na faixa de 57,5 ¿ 67,5 ºC e pH entre 4,7 ¿ 5,5, além de meia vida de 21,33 horas a 52ºC e pH 5,3, com vmax de 1,77 µmol/mL.min e Km de 0,44 g/L. Já a enzima produzida pela cepa AY10 possui condições ótimas na faixa de pH entre 4,8 ¿ 4,1 à temperatura de 80°C, além de meia vida de 11,21 horas a 72ºC e pH 5,3, com vmax de 5,47 µmol/mL.min e Km de 1,37 g/L. Estes resultados demonstram o potencial de aplicação de leveduras na produção de xilanase, porém, para as cepas estudadas, há a necessidade de purificação das enzimas produzidas para que estas sejam aplicadas industrialmente / Abstract: Endo-1,4-ß-xylanase (E.C. 3.2.1.8), commonly called xylanase, has great application in different types of industries such as feed, food, textiles, paper, ethanol from biomass, among others. These enzymes act in hydrolysis of the xylan, one of the most abundant polysaccharides found in the nature, present in cell plants linked to the hemicelullose. The main goal of this work was to select, through a screening method using Petri dishes, and to evaluate the enzymatic activity of isolated wild yeasts from several brazilian regions (Atlantic Forest, Amazonian Forest, Cerrado and Pantanal) about the production of xylanase. For the screening in Petri dishes, the culture medium used has xylan as the only carbon source to induce the production of the enzyme. From 349 evaluated microorganisms, 84 could produce xylanase, although only 37 showed an enzymatic ration (diameter of the undye halo/diameter of the colony) higher than 2.5. And, after initial assays in submerged method, 9 strains showed a satisfactory growth at 30ºC and 150 rpm. Among them, the microorganisms AAD5 and AY10 presented a higher potential, with the enzymatic activity above 2 µmol/mL.min. The characterization of the produced enzymes was carried out and the one produced by the strain AAD5 has, as optimal conditions, temperature between 57.5 ¿ 67.5 ºC and pH 4.7 ¿ 5.5. Also, it was shown 21.33 hours of half-life at 52ºC and pH 5.3, with vmax of 1.77 µmol/mL.min and Km of 0.44 g/L. The enzyme produced by the strain AY10 has, as optimal conditions, pH between 4.8 ¿ 4.1 and temperature around 80ºC. The half-life of the enzyme was 11.21 hours at 72ºC and pH 5.3, with vmax of 5.47 µmol/mL.min and Km of 1.37 g/L. These results demonstrate the potential application of the yeasts for xylanase production, although, for those enzymes, further works are necessary to establish the actual industrial and technical potentialities / Mestrado / Mestre em Engenharia de Alimentos

Orientador: Francisco Maugeri Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-15T18:37:14Z (GMT). No. of bitstreams: 1 Motta_FernandaLopes_M.pdf: 741375 bytes, checksum: 2dd5dcca312294d6118957b0bf359271 (MD5) Previous issue date: 2010 / Resumo: O interesse no estudo dos sistemas das xilanases vem sendo estimulado pela sua utilidade em uma variedade de processos biotecnológicos. Estas enzimas podem ser aplicadas em indústrias de panificação, melhorando a textura, o volume da massa e o tempo de prateleira dos produtos; em vinícolas e cervejarias, favorecendo a etapa de filtração e a clarificação, além de ser adicionada à ração animal de aves e suínos para aumentar a digestibilidade. Diante da importância da aplicação das xilanases e da necessidade desenvolver condições que otimizem a produção dessas enzimas a fim de tornar sua utilização comercial menos restrita, estudos têm sido realizados visando obter maior produtividade e substratos de baixo custo. O objetivo deste trabalho foi otimizar a produção de xilanase a partir de uma cepa de levedura silvestre isolada da Mata Atlântica utilizada em estudo anterior, indicando potencial para produção de uma enzima estável. Duas cepas foram testadas inicialmente a fim de selecionar a mais adequada para este estudo. Uma vez selecionada, a cepa foi utilizada para testar a influência do tampão fosfato sobre a produção de xilanase e os resultados mostraram que a adição de tampão fosfato ao meio de cultura exerce um efeito negativo tanto em relação à biomassa da levedura quanto à produção e atividade da enzima. A partir desses resultados optou-se pela exclusão do tampão do meio e foi aplicado um planejamento experimental variando as condições de fermentação visando a otimização da produção da xilanase. Primeiramente, realizou-se um delineamento Plackett & Burman (PB) para determinar os efeitos principais das sete variáveis estudadas em relação à atividade enzimática, onde a temperatura e a concentração de xilanase foram consideradas estatisticamente significativas. Em seguida, realizou-se um Delineamento Composto Central Rotacional (DCCR) de 11 ensaios onde as variáveis independentes foram aquelas consideradas significativas pelo PB. Os resultados obtidos pelos DCCR foram analisados por ferramentas estatísticas que confirmaram a confiabilidade do modelo preditivo para a atividade da enzima xilanase. De acordo com este modelo, a máxima atividade enzimática (67,45 UI) foi encontrada para os pontos centrais do planejamento, onde a concentração de xilana foi de 20 g.L-1 e a temperatura de 30°C / Abstract: The interest in the study of systems of xylanases has been stimulated by its usefulness in a variety of biotechnological processes. These enzymes could be applied to bakery, improving texture, volume and mass of the shelf life of products, wineries and breweries, supporting the step of filtration and clarification; also it could be added in poultry and pigs feed to increase digestibility. Due to this importance of application of xylanases and the necessity to develop conditions that optimize the production of these enzymes in order to make its commercial use less restricted, studies have been done to achieve higher productivity with low cost substrates. The objective of this work was to optimize the production of xylanase from a wild yeast strain isolated from Mata Atlântica. Two strains were tested initially in order to select the most appropriated one for this study. Once selected, it was tested the influence of phosphate buffer on the production of xylanase and the results showed that the addition of phosphate buffer to the culture medium has a negative effect on yeast biomass and activity enzyme produced. From these results it was decided to exclude the buffer used in medium and it was applied an experimental design aimed to optimize the conditions for xylanase production. At first, a design Plackett & Burman (PB) was done to determine the main effects of each variable studied in relation to enzymatic activity, where the temperature and the concentration of xylanase were considered statistically significant. Then, a central composite rotational design (DCCR) of 11 trials was carried out, where the independent variables were those considered significant by the PB. The results obtained by DCCR were analyzed by statistical tools that confirmed the reliability of the predict model to the xylanse activity enzyme. According to this model, the maximum enzyme activity (67,45 UI) was found at the central points of planning, where the concentration of xylan was 20 gL-1 and temperature of 30 ° C / Mestrado / Mestre em Engenharia de Alimentos

Xylan dissolved during kraft cooking and later redeposited on fibre surfaces has been shown to give higher pulp yield and better strength properties. This is economically interesting from an industrial point of view. Many studies have been done to investigate xylan behaviour during kraft cooking, to discover the xylan-cellulose attachment mechanism, to find the optimal xylan retention or adsorption process, and to discover relations between xylan structure and strength enhancement. Most of them have concentrated on hardwood xylan. However, softwoods are the major raw materials for the pulp industries in the northern hemisphere. Earlier studies have shown that the xylan characteristics, rather than simply the amount of xylan, influence the strength-enhancing effect of xylan. To obtain optimal utilization of spruce xylan as a strength enhancer, it is essential to know what the beneficial xylan characteristics are and how cooking conditions affect the characteristics. In this study, kraft cooking of spruce chips was performed under varied cooking conditions and the xylan in the black liquor was precipitated and characterized. It was found that dissolved spruce xylan had a much higher amount of bound lignin compared to previous studies on xylan dissolved from hardwoods. Increased cooking temperature increased the dissolution rate of xylan. The lower alkali charge and higher ionic strength of the cooking liquor resulted in a lower amount of dissolved xylan. Apart from the effect of the amount, cooking conditions also affected substitution of dissolved xylan. Higher temperature and higher ionic strength led to a lower amount of MeGlcA, while the MeGlcA amount of dissolved xylan was preserved during lower alkali cooking. By distinguishing how different cooking conditions affect the characteristics of the xylan dissolved in the black liquor, xylans with different structures were designed to study their effects on pulp strength, that is, the addition of black liquors with certain known xylan characteristics in the kraft cooking process. It was found that the best effect of xylan on tensile strength occurred when the xylan penetrated some distance into the subsurface of the fibre wall. Both low molecular weight and high degree of substitution lowered the tendency of xylan to aggregate, which enabled the dissolved xylan to penetrate some distance into the exposed fibre surface. Upon beating, this xylan was exposed, thus facilitating improvement of fibre-fibre joint formation, which led to increased tensile strength. / <p>QC 20130326</p>

Glycerol thermal processing (GTP) is studied as a novel biomass pretreatment method in this research with the purposes to facilitate biopolymer fractionation and biomass saccharification. This approach is performed by treating sweet gum particles on polymer processing equipment at high temperatures and short times in the presence of anhydrous glycerol. Nine severity conditions are studied to assess the impact of time and temperature during the processing on biopolymer structure and conversion. The GTP pretreatment results in the disruption of cell wall networks by increasing the removal of side-chain sugars and lignin-carbohydrate linkages based on severity conditions. After pretreatment, 41% of the lignin and 68% of the xylan is recovered in a dry powdered form by subsequent extractions without additional catalysts, leaving a relatively pure cellulose fraction, 84% glucan, as found in chemical pulps. Lignin structural analysis indicated GTP processing resulted in extensive degradation of B-aryl ether bonds through the C-y elimination, followed by abundant phenolic hydroxyl liberation. At the same time, condensation occurred in the GTP lignin, providing relatively high molecular weight, near to that of the enzymatic mild acidolysis lignin. Better thermal stability was observed for this GTP lignin. In addition to lignin, xylan was successfully isolated as another polymer stream after GTP pretreatment. The recovered water insoluble xylan (WIX) was predominant alkali soluble fraction with a maximum purity of 84% and comparable molecular weight to xylan isolated from non-pretreated fibers. Additionally, the narrow molecular weight distribution of recovered WIX, was arisen from the pre-extraction of low molecular weight water-soluble xylan. Additionally, a 20-fold increase of the ultimate enzymatic saccharification for GTP pretreated biomass was observed even with significant amounts of lignin and xylan remaining on the non-extracted fiber. The shear and heat processing caused a disintegrated cell wall structure with formation of biomass debris and release of cellulose fibrils, enhancing surface area and most likely porosity. These structural changes were responsible for the improved biomass digestibility. Additionally, no significant inhibitory compounds for saccharification are produced during GTP processing, even at high temperatures. While lignin extraction did not promote improvement in hydrolysis rates, further xylan extraction greatly increases the initial enzymatic hydrolysis rate and final level of saccharification. The serial of studies fully demonstrate glycerol thermal processing as a novel pretreatment method to enhance biomass saccharification for biofuel production, as well as facilitate biopolymer fractionation. Moreover, the study shows the impact of thermally introduced structural changes to wood biopolymers when heated in anhydrous environments in the presence of hydrogen bonding solvent. / Ph. D.

A large part of the world paper manufacturing consists of production of corrugated board components, kraftliner and fluting, that are used in many different types of corrugated boxes. Because these boxes are stored and transported, they are often subjected to changes in relative humidity. These changes together with mechanical loads will increase the deformation of the boxes compared to the case where the same loads are applied in a static environment. This enlarged creep due to the changes in relative humidity is called mechano-sorptive or accelerated creep. Mechano-sorptive creep forces producers to use high safety factors when designing boxes, and therefore, this is one of the key properties of kraftliner boards.   Different strategies to decrease mechano-sorptive creep, and to simultaneously gain more knowledge about the causes for this phenomenon in paper, are the aim of this work. Derivatised and underivatised black liquor lignins, a by-product produced in pulp mills in large quantities, have been used together with biomimetic methods, to modify the properties of kraftliner pulp. Furthermore, the properties of kraftliner pulp have been compared to other pulps in order to evaluate the influence of fibre morphological factors, such as fibre width and shape factor, on the mechano-sorptive creep. In addition the influence of the chemical composition of the kraftliner pulp has been evaluated both by means of treating a kraftliner pulp with chlorite and xylanase and by producing pulps with different chemical composition.   By using lignin and biomimetic methods, to create radical coupling reactions, it has been shown that it is possible to increase the wet strength of kraftliner pulp sheets. This method of treating the pulp showed, however, no significant effects on the mechano-sorptive creep. The addition of an apolar suberin-like lignin derivative, which has been shown to be possible to produce from natural resources, did show a positive effect on mechano-sorptive creep properties, but at the expense of stiffness properties in constant climate. Different pulps were compared with a kraftliner pulp and it was observed that the ratio between tensile stiffness and hygroexpansion can be used to estimate the mechano-sorptive creep properties. The hardwood kraft pulps investigated had lower hygroexpansion, probably due to more slender and straighter fibres, and higher tensile stiffness, probably due to lower lignin content. As the lignin content was varied by different methods in kraft pulps, it was observed that increased lignin content gives an increased hygroexpansion and decreased tensile stiffness as well as an increased mechano-sorptive creep. There were also indications of increased mechano-sorptive creep due to higher xylan content. / En stor del av världens papperstillverkning utgörs av produktion av wellpappkomponenter, kraftliner och fluting, som används i en uppsjö av olika wellpapplådor. När dessa lådor lagras och transporteras utsätts de ofta för förändringar i relativa luftfuktigheten. Dessa förändringar tillsammans med mekanisk belastning ökar lådornas deformation jämfört med om samma belastning skulle ha applicerats vid ett statiskt klimat. Denna förhöjda krypning på grund av förändringarna i relativ luftfuktighet kallas mekanosorptiv- eller accelererad krypning. Mekanosorptiv krypning tvingar producenterna att ha höga säkerhetsmarginaler vid dimensioneringar av lådor och är därför en av nyckelegenskaperna för kraftliner.   Olika strategier för att minska denna effekt, och på samma gång erövra mer kunskap om orsakerna till detta fenomen, har varit syftet med arbetet. Derivatiserade och oderivatiserade svartlutslignin, en biprodukt möjlig att få ut i stora kvantiteter från massabruk, har används tillsammans med biomimetriska metoder, för att modifiera kraftlinermassas egenskaper. Dessutom har kraftlinermassans egenskaper jämförts med andra massors egenskaper för att utvärdera inverkan av fibermorfologiska faktorer, såsom fiberbredd och fibreform på det mekanosorptiva krypet. Också inverkan av den kemiska sammansättningen av kraftliner massan har undersökts både genom behandling med klorit och xylanas och genom att producera massor med olika kemiska sammansättningar.   Genom att använda lignin och biomimetriska metoder för att skapa radikal-kopplingsreaktioner har det visats på möjligheten att öka våtstyrkan i massa-ark. Det här sättet att behandla massa visade dessvärre inga signifikanta effekter på det mekanosorptiva krypet. Tillsatts av ett apolärt suberin-liknande ligninderivat, som visats möjligt att producera ur naturliga råmaterial, visade en positiv effekt på det mekanosorptiva krypegenskaperna även om det var på bekostnad av styvheten vid konstant klimat. Olika massor jämfördes med en kraftlinermassa och det observerades att relationen mellan dragstyvhet och hygroexpansion kan användas för att uppskatta de mekanosorptiva krypegenskaperna. Lövvedssulfatmassorna som undersöktes hade lägre hygroexpansion, antagligen beroende på smalare och rakare fibrer, och högre dragstyvhet, troligen beroende på en lägre ligninhalt. När ligninhalten varierades i sulfatmassor med olika metoder observerades att ökad ligninhalt ger en ökad hygroexpansion och minskad dragstyvhet liksom en ökad mekanosorptiv krypning. Dessutom fanns indikationer på en ökad mekanosorptiv krypning till följd av högre xylaninnehåll. / QC 20100629

The sulfite pulping process is today practised in only a small number of pulp mills around the globe and the number of sulfite mills that use sodium as the base (cation) is less than five. However, due to the increasing interest in the wood based biorefinery concept, the benefits of sulfite pulping and especially the sodium based variety, has recently gained a lot of interest. It was therefore considered to be of high importance to further study the sodium based sulfite process to investigate if its benefits could be better utilized in the future in the production of dissolving pulps. Of specific interest was to investigate how the pulping conditions in the initial part of the cook (≥ 60 % pulp yield) should be performed in the best way. Thus, this thesis is focused on the initial phase of single stage sodium bisulfite cooking of either 100 % spruce or 100 % pine wood chips. The cooking experiments were carried out with either a lab prepared or a mill prepared cooking acid and the temperature and cooking time were varied. Activation energies for different wood components were investigated as well as side reactions concerning the formation of thiosulfate and sulfate. / Single stage sodium bisulfite cooking was carried out on either spruce or pine wood chips to investigate the influence of several process parameters in the initial phase of such a cook i.e. between 100 % and 60 % pulp yield. The cooking experiments were carried out with either a lab prepared or a mill prepared cooking acid and the temperature and time in the initial stage were varied. The influence of dissolved organics and inorganics components in the cooking liquor on the final pulp properties and side reactions were investigated. The impact of temperature and time on the pulp components were analyzed with respect to carbohydrates, lignin, extractives and thiosulfate. Kinetic equations were developed and the activation energies for delignification and carbohydrate dissolution were calculated using the Arrhenius equation. It was found that if using a mill prepared cooking acid, this had a beneficial effect with respect to side reactions, better extractives removal and higher pH stability during the cook, compared to a corresponding cook with a lab prepared cooking acid. Cooking with mill prepared and lab prepared cooking acids showed the same behaviour with respect to delignification and carbohydrate degradation, but the lab acid experiments resulted in a higher thiosulfate formation during the cook. The cellulose yield was not affected at all during the initial phase of the sulfite cook verifying earlier results by other researchers. The temperature had an influence on both the delignification rate and the rate of hemicelluloses removal.  The corresponding activation energies were found to increase in the following order; cellulose, xylan, glucomannan and lignin. / <p>Artikel 1: "The Initial Phase of Sodium Bisulfite Pulping of Spruce: Part 1" ingick i avhandlingen som manuskript. Nu publicerad.</p>

Thesis (PhD (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: There is growing interest to utilise xylan as speciality biopolymers in similar ways as high molecular weight polysaccharides such as starch and cellulose. The need to utilise xylan as alternative to cellulose and starch has increased because the cellulose and starch have many other competing uses. Unlike cellulose and starch, xylans are heteropolymers with higher degree of substitution and are of lower molecular mass and therefore, do not readily become insoluble to form hydrogels and biofilms. Consequently, xylans do not suit applications of starch and cellulose as speciality biodegradable additives and coatings in the food, pharmaceutical, pulp and paper and textile and many other industries. This study was conducted to develop an enzyme technology, based on recombinant α-L-arabinofuranosidase and purified α-D-glucuronidase with polymeric xylan substrate specificity, for controlled reduction of the solubility of water soluble polymeric xylan, leading to formation of insoluble nanohydrogels. Although xylan is available in abundance, a large proportion of it is currently wasted in lignocellulose process waste streams with little prospects for recovery and addition of value. Lignocellulosic materials including Eucalyptus grandis, Pinus patula, Bambusa balcooa (bamboo) and sugarcane (Saccharum officinarum L) bagasse (bagasse) found in South Africa were investigated as sources of water soluble xylan for enzyme modification. Two mild alkali-low temperature methods (alkali charge of < 14% and temperature of < 80ºC), one with ultrapurification denoted as the Hoije and the other with ethanol precipitation, denoted as Lopez method, were evaluated for their selective extraction of water soluble xylans from the specified lignocellulosic materials. The water soluble xylans were extracted from P. patula, bagasse, E. grandis and bamboo by the Hoije method with extraction efficiencies of 71.0, 66.0, 35.0 and 20.0% respectively. Using the Lopez method, the xylans from bagasse and E. grandis were extracted with extraction efficiencies of 28.0 and 12.0% respectively. The xylans extracted from P. patula, bamboo and bagasse were identified as arabinoglucuronoxylans, which were substituted with arabinose and 4-O-methyl-D- glucuronic acid (MeGlcA) side chains, whereas, the xylan extracted from E. grandis were identified as 4-O-methyl-β-D-glucuronoxylan (glucuronoxylan) substituted with MeGlcA groups on the main xylan chain. In addition, the glucuronoxylans contained some traces of arabinose and rhaminose sugar residues. The extracted xylan fractions had degree of polymerisation (DP) of > 10 and were water soluble, which suited the required properties of xylans for customised enzyme modification. The selective removal of the arabinose, MeGlcA and acetyl groups to create linear regions of xylose units in xylans that causes intra and inter-polymer bonding is considered to be the key process for reducing the solubility of water soluble xylans. The α-L-arabinofuranosidase of Aspergillus niger (AbfB) and α-D-glucuronidase of Schizophyllum commune (AguA) are special enzymes so far identified with the ability to selectively remove arabinose and MeGlcA side chains respectively, from water soluble xylans. Large scale application of the AbfB and AguA for reducing solubility of the water soluble xylans would require their extracellular production in large quantities and free of contamination from the xylan main chain degrading enzymes including the endo-1,4-β -xylanase. Selective production of the AbfB free of xylanase activity was achieved in recombinant A. niger D15 [abfB] strain under the transcriptional control of the glyceraldehyde-3-phosphate dehydrogenase promoter (gpdP) and glucoamylase terminator (glaAT). The recombinant AbfB was secreted extracellulary in 125 mL shake flasks and 10 L bioreactor fermentation cultures with volumetric activities of up to 10.0 and 8.0 nkat mL-1 respectively, against para-nitrophenol arabinofuranoside (pNPA). The secretion of the recombinant AbfB was growth associated and therefore, increased up to 2.5 times with addition of concentrate corn steep liquor (CCSL) as an additional source of nitrogen in the 2 x minimal standard cultivation media. The biomass specific activity of the recombinant AbfB against the pNPA substrate was approximately 366 nkat g-1 (dry weight basis). The recombinant AbfB displayed a single pure species band on 10% SDS-PAGE stained with Coomassie blue and had an estimated molecular mass of 67 kDa. In addition, the recombinant AbfB showed optimal activity at 40-55ºC and pH 3.0-5.0 and was stable under cultivation, storage and operating conditions at temperatures between 30-60ºC and pH 3.0-6.0. Furthermore, the recombinant AbfB showed broad substrate specificity selectively removing arabinose side groups from low viscosity wheat and oat spelt arabinoxylans, larchwood arabinogalactan, debranched arabinan and arabiglucuronoxylans extracted from bagasse, bamboo and P. patula found in South Africa,. The recombinant AbfB was able to precipitate xylans extracted from bagasse, bamboo and oat spelt but not from P. patula. Over 95% of the activity of the recombinant AbfB against the pNPA was recyclable after selective hydrolysis of the xylan at 40ºC for 16 h. On the other hand, the purified AguA enzyme could only precipitate the birch glucuronoxylan but not the glucuronoxylan extracted from E. grandis and arabinoglucuronoxylans extracted from bagasse, bamboo and P. patula. The synergetic action of the recombinant AbfB and the purified AguA increased the removal of the arabinose side chains from bagasse xylan by 22% and from bamboo xylan by 33%, whereas, the removal of the MeGlcA side chains from bagasse xylan increased by only 5% and that from bamboo xylan decreased by 13%. The selective removal of the arabinose side chains from oat spelt, bagasse and bamboo xylans by the recombinant AbfB had higher apparent viscosity relative the corresponding untreated xylans. However, the apparent viscosity of both the treated and untreated xylans reduced with increased shear rate. The viscosity had an overall negative correlation with arabinose side chain removal reaching a minimum of 2.03 mPa.s for hydrolysis of oat spelt xylan that was performed for 9.0 h at a temperature of 45.8ºC with recombinant AbfB xylan specific dosage of 400.0 nkat g-1substrate . The alteration of the viscosity of the xylans by the selective removal of the side chains is of special interest in the production of speciality emulsifying, thickening and antifoaming agents. The optimal values for hydrolysis time, enzyme dosage and temperature for maximum degree of removal of arabinose side chains from oat spelt xylan by the recombinant AbfB and of the removal of MeGlcA side chains from birch xylan by the purified AguA were determined by the Box-Benhken response surface method (RSM). The experimental region covered the xylan specific dosage for the recombinant AbfB between 18.0 and 540.0 nkatg-1substrate and for the purified AguA xylan between 2.0 and 18.0 μkatg-1substrate at temperatures between 30 and 50ºC and hydrolysis time between 1 and 16 h. The temperature, enzyme xylan specific dosage and hydrolysis time had significant effect (p<0.05) on both the selective removal of arabinose from oat spelt xylan by the recombinant AbfB and the selective removal of MeGlcA from birch xylan by the purified AguA. However, the interaction of these hydrolysis parameters were significant (p<0.05) on only the removal of arabinose side chains from oat spelt xylan by the recombinant AbfB. The optimal values for hydrolysis time, temperature and xylan specific dosage were estimated to be 14-16 h, 38-45ºC and 607.0 nkatg-1substrate respectively, for maximum removal of 43% of the available arabinose in oat spelt xylan by the recombinant AbfB. Whereas, the optimal values for hydrolysis time, temperature and xylan specific dosage for maximum removal of 0.5% of the available MeGlcA side chains from the birch xylan by the purified AguA were estimated to be 11 h, 38ºC and 18.0 μkatg-1substrate respectively. The optimal values of the hydrolysis parameters for both the removal of the arabinose from oat spelt xylan by the recombinant AbfB and of MeGlcA side chains from birch by the purified AguA could be predicted using quadratic models that fitted the response surface plots with regression coefficients of > 0.9. The effects of in situ selective removal of arabinose and MeGlcA side chains by AbfB and AguA respectively, from water soluble xylans, on their precipitation and adsorption onto cotton lint were investigated. The cotton lint was treated with xylans extracted from bagasse, bamboo, P. patula and E. grandis using the Hoije method in the presence of the recombinant AbfB, AguA and the cocktail of the two enzymes. The effects of in situ selective hydrolysis of model xylans including birch, oat spelt and H2O2 bleached bagasse and E. grandis xylan gel by the enzymes on their adsorption onto cotton lint were used for reference purposes. The purified AguA increased the adsorption of arabinoglucuronoxylans extracted from bagasse bamboo and P. Patula using the Hoije method onto cotton lint the most compared to the effect of the recombinant AbfB and the cocktail of the recombinant AbfB and purified AguA. The purified AguA increased the adsorption of the xylans extracted from bagasse and E. grandis xylans by 334 and 29% respectively, but decreased that of E. grandis xylan gel and H2O2 bleached bagasse xylan by 31 and 6% respectively. Similarly, the presence of the recombinant AbfB increased the adsorption of the bamboo, P. Patula and oat spelt xylans by 31, 44 and 900% respectively, but decreased the adsorption of the xylan extracted from bagasse and the H2O2 bleached bagasse xylan by 13 and 30% respectively. Furthermore, different xylan-cellulose interactions and water adsorption capacities of the cotton lint were observed with the in situ modification and adsorption of the xylans extracted from bagasse, bamboo, E. grandis and P. patula in the presence of the recombinant AbfB and purified AguA. Therefore, the enzyme aided adsorption of xylans could be used to alter or improve functional properties of cellulosic materials. The performance of enzymatically formed xylan nanohydrogels as encapsulation matrices for slow delivery of bioactive agents was evaluated. Insoluble xylan nanohydrogels formed by selective removal of arabinose side chains from water soluble oat spelt xylan by the recombinant AbfB were characterized for particle size distribution, surface charge (zeta potential), morphology stability and ability to encapsulate and slowly release the HRP. The enzymatically formed oat spelt xylan hydrogels were spherical in shape with particle sizes ranging from 18 nm to > 10 000 nm. The xylan nanohydrogels exhibited a negative zeta potential of up to -19 mV and displayed self assembling behaviour when formed at xylan concentrations of higher than 1.5% (w/v) and hydrolysis time beyond 17 h. The xylan concentration significantly (P < 0.05) influenced both the particle size and zeta potential of the oat spelt xylan nanohydrogels whereas the recombinant AbfB hydrolysis time was significant (P < 0.05) on the zeta potential. The oat spelt xylan nanohydrogels successfully encapsulated the HRP enzyme both during and after formation of the oat spelt xylan nanohydrogels and the release of the encapsulated HRP in active form, was sustained for a period of 180 min. Therefore, the xylan side chain removing enzymes have a role in preparation of biodegradable nanoencapsulation devices. Overall, the AbfB and AguA have presented a novel tool for functionalising water soluble xylans to be used as speciality additives, coating and implantation or encapsulation matrices, with reduced impact on the environment. This will advance processing and expand the product spectrum of lignocellulosic materials. / AFRIKAANSE OPSOMMING: Daar is ‘n toenemende belangstelling om spesialiteit biopolimere uit xilaan ontwikkel, en op soortgelyke wyse as hoë molekulêre massa polisakkariede soos stysel en sellulose te benut. Die behoefte om xilaan biodegradeerbare polimere as ‘n alternatief tot sellulose en stysel te gebruik neem toe omdat laasgenoemde baie ander kompeterende gebruike het. Anders as sellulose en stysel is uit xilaan heteropolimere met ‘n hoë graad van substitusie in die hoofketling met sygroepe en lae molekulêre massas, en raak daarom nie geredelik onoplosbaar om hidrojel en biofilms te vorm nie. Gevolglik is xilaan nie geskik vir toepassings van stysel en sellulose as spesialiteit biodegradeerbare bymiddels en bedekkings in die voedsel-, farmaseutiese-, pulp en papier-, tekstiel-, en vele ander industrieë nie. Hierdie studie is uitgevoer om ‘n ensiemtegnologie te ontwikkel gebaseer op rekombinante α-L-arabinofuranosidase en gesuiwerde α-D-glukuronidase met polimeriese xilaan substraat spesifisiteit, vir beheerde vermindering van die oplosbaarheid van wateroplosbare polimeriese xilaan wat lei tot die vorming van onoplosbare nanohidrojels. Alhoewel xilaan volop beskikbaar is, word ‘n groot deel daarvan tans vermors in afvalstrome uit lignosellulose prosessering, primêr verpulping, met min vooruitsigte vir herwinning en toevoeging van waarde. Lignosellulose materiaal wat in Suid-Afrika geproduseer word, insluitend Eucalyptus grandis (E. grandis), Pinus patula (P. patula), Bambusa balcooa (bamboes) en suikerriet (Saccharum officinarum L) (bagasse), is ondersoek as bronne van wateroplosbare xilaan vir ensiem modifikasie. Twee gematigde, lae temperatuur alkali-metodes (‘nalkali lading van < 14% en temperatuur van < 80°C), een met ultrasuiwering aangedui as Hoije en die ander met etanolpresipitasie aangedui as Lopez metode, is evalueer vir selektiewe ekstraksie van wateroplosbare xilaan vanuit die genoemde lignosellulose materiale. Die wateroplosbare xilaan is ge-ekshaheer vanuit P. patula, bagasse, E. grandis en bamboes met die Hoije metode met ekstraksie doeltreffendhede van 71.0, 66.0, 35.0, en 20.0%, onderskeidelik. Met die Lopez metode is xilaan vanuit bagasse en E. grandis geëkstraheer met ekstraksie doeltreffendhede van 28.0% en 12.0%, onderskeidelik. Die xilaan wat vanuit P. patula, bamboes, en bagasse ekstraheer is, is as arabinoglukuronoxilaan geïdentifiseer, wat met arabinose en 4-O-metiel-D glukuronsuur sykettings vervang is, terwyl die xilaan wat vanuit E. grandis ekstraheer is as 4-O-metiel--D-glukuronoxilaan (glukuronoxilaan), met substitusie met MeGlcA en asetiel-groepe op die hoof xilaan-ketting (ruggraat) is. Die glukuronoxilaan het verder spore van arabinose en rhaminose funksionele groepe bevat. Die geëkstraheerde xilaan fraksies het grade van polimerisasie > 10 gehad en was wateroplosbaar, wat die vereiste eienskappe van die xilaan vir doelgemaakte ensiem modifikasies bevredig het. Die selektiewe verwydering van die arabinose, MeGlcA, en asetiel-groepe om xilose eenhede sonder substitusie in polimeriese xilaan te vorm, wat intra- en inter-polimeer binding veroorsaak, word beskou as die belangrikste proses vir die vermindering van die oplosbaarheid van wateroplosbare xilaan. Die α-L-arabinofuranosidase van Aspergillus niger (AbfB) en α-D-glukuronidase van Schizophyllum commune (AguA) is spsialiteutsensieme wat tot dusver is met die vermoë om selektief die arabinose en MeGlcA sykettings, onderskeidelik, vanaf wateroplosbare xilaan te verwyder. Grootskaalse toepassing van die AbfB en AguA ensieme, vir die vermindering van die oplosbaarheid van wateroplosbare xilaan , sal ekstrasellulêre produksie deur mikrobes in groot hoeveelhede en vry van kontaminasie van die xilaan hoofketting degraderende ensieme insluitend die endo-1,4--xilanase vereis. Selektiewe produksie van die AbfB vry van xilanase aktiwiteit is verkry deur kultivering van rekombinante A. niger D15 [abfB], met transkipsie van die abfB-geen beheer deur die gliseraldehied-3-fosfaat dehidrogenase promotor (gpdp) en glukoamilase termineerder (glaAT). Die rekombinante AbfB ensiem is ekstrasellulêr geproduseer in 125 mL skudflesse en ‘n10 L bioreaktor fermentasiekulture met volumetriese aktiwiteite van tot 10.0 en 8.0 nkat mL-1, onderskeidelik, teen para-nitrofenol arabinofuranosied (pNPA). Die uitskeiding van die rekombinante AbfB was groei geassosieerd en het daarom tot 2.5 keer toegeneem met die byvoeging van gekonsentreerde mielieweekvloeistof as ‘n addisionele bron van stikstof in die 2 x minimale standaard kwekingsmedium. Die biomassa spesifieke aktiwiteit van die rekombinante AbfB teen die pNPA substraat was ongeveer 366 nkat g-1 (droë massa basis). Die rekombinante AbfB het ‘n enkele suiwer spesie band getoon op 10% SDS-PAGE gevlek met Coomassie blou en het ‘n beraamde molekulêre massa van 67 kDa gehad. Die rekombinante AbfB het verder optimale aktiwiteit by 40-55°C en pH 3.0-5.0 getoon en was stabiel onder kweking-, storing-, en bedryfstoestande by temperature tussen 30-60°C en pH 3.0-6.0. Die rekombinante AbfB het ook wye substraatspesifisiteit getoon om arabinose sy-groepe selektief te verwyder vanaf lae viskositeit koring-en hawerbiopolimere, lariks arabinogalaktaan, onvertakte arabinaan, en arabinoglukuronoxilaan biopolimere, geëkstraheer vanaf bagasse, bamboes en P.patula wat in Suid-Afrika aangetief word. Die rekombinante AbfB kon xilaan, ge-ekshaheer vanaf bagasse, bamboes en hawer onoplosbaar maak, maar die xilaan geëkstraheer vanaf P. patula nie. Meer as 95% van die aktiwiteit van die rekombinante AbfB teen die pNPA kon hersirkuleer word na selektiewe hidrolise van die xilaan by 40°C vir 16 h. Aan die ander kant kon die gesuiwerde AguA-ensiem slegs berkehout glukuronoxilaan onoplosbaar maak, maar nie glukuronoxilaan wat vanaf E. grandis geëkstraheer is of arabinoglukuronoxilaan wat vanaf bagasse, bamboes en P. patula geëkstraheer is nie. Die sinergistiese aksie van die rekombinante AbfB en die gesuiwerde AguA het die verwydering van die arabinose sykettings vanaf bagassexilaan met 22% vermeerder en met 33% in die geval van bamboesxilaan. Die verwydering van MeGlcA sykettings vanaf bagassexilaan is met slegs 5% vermeerder, terwyl dit met 13% verminder het in die geval van bamboesxilaan. Die selektiewe verwydering van die arabinose sykettings vanaf xilaan van hawer, bagasse, en bamboes deur die rekombinante AbfB het hoër skynbare viskositeit gehad relatief tot die ooreenstemmende onbehandelde xilaan . Die skynbare viskositeit van beide die behandelde en onbehandelde xilaan het egter verminder met toenemende skuiftempo. Die viskositeit het ‘n algehele negatiewe korrelasie met arabinose syketting verwydering gehad en het ‘n minimum van 2.03 mPa.s bereik vir hidrolise van hawerxilaan wat uitgevoer is vir 9.0 h by ‘n temperatuur van 45.8°C met rekombinante AbfB xilaan met ‘n spesifieke dosering van 400.0 nkat g-1substraat. Die wysiging van die viskositeit van die xilaan deur die selektiewe verwydering van die sykettings is van besondere belang in die produksie van spesialiteit emulsifisering, verdikking- en skuimweermiddels. Die optimale waardes vir hidrolisetyd, ensiemdosering en temperatuur vir maksimum graad van arabinose syketting verwydering vanaf hawerxilaan met die rekombinante AbfB, en van MeGlcA syketting verwydering vanaf berkehout xilaan met die gesuiwerde AguA, is vasgestel deur middel van die Box-Benhken responsie oppervlak metode. Die eksperimentele gebied het die xilaanspesifieke dosering met die rekombinante AbfB tussen 18.0 en 540.0 nkat g-1substraat en vir die gesuiwerde AguA xilaan tussen 2.0 en 18.0 μkat g-1substraat by temperature tussen 30 en 50°C en hidrolisetye tussen 1 en 16 h gedek. Die temperatuur, ensiem xilaan spesifieke dosering en hidrolise tyd het elk ‘n beduidende invloed (p<0.05) gehad op beide die selektiewe verwydering van arabinose vanaf hawerxilaan met die rekombinante AbfB en die selektiewe verwydering van MeGlcA vanaf berkehout xilaan met die gesuiwerde AguA. Die interaksie van hierdie hidroliseparameters was egter net beduidend (p<0.05) in die geval van arabinose syketting verwydering vanaf hawer xilaan met die rekombinante AbfB. Die optimale waardes vir die hidrolise tyd, temperatuur, en xilaan spesifieke dosering is beraam om gelyk aan 14-16 h, 38-45°C, en 607.0 nkat g-1substraat, onderskeidelik, te wees vir maksimale verwydering van 43% van die beskikbare arabinose in die hawer xilaan met die rekombinante AbfB. Die optimale waardes vir die hidrolise tyd, temperatuur en xilaan spesifieke dosering vir maksimale verwydering van 0.5% van die beskikbare MeGlcA sykettings vanaf die berkehout xilaan met die gesuiwerde AguA is beraam om gelyk aan 11 h, 38°C, en 18.0 μkat g-1substraat, onderskeidelik, te wees. Die optimale waardes van die hidrolise parameters, vir beide die verwydering van die arabinose vanaf hawer xilaan met die rekombinante AbfB en van MeGlcA sykettings vanaf berkehout met die gesuiwerde AguA, kon voorspel word deur gebruik te maak van kwadratiese modelle wat die responsie-oppervlak grafieke met regressie koeffisiënte > 0.9 gepas het. Die effek van in situ selektiewe verwydering van arabinose en MeGlcA sykettings met rekombinante AbfB en gesuiwerde AguA, onderskeidelik, vanaf wateroplosbare xilaan op hulle presipitasie en adsorpsie op katoen lint is ondersoek. Die katoenlint is behandel met xilaan ge-ekstraheer vanuit bagasse, bamboes, P. patula, en E. grandis deur gebruik te maak van die Hoije metode in die teenwoordigheid van die rekombinante AbfB, AguA, en ‘n mengsel van die twee ensieme. Die effek van in situ selektiewe hidrolise, deur die ensieme van model xilaan insluitende berkehout, hawer en H2O2-gebleikte bagasse en E. grandis xilaan jel, op hulle adsorpsie op katoen lint is gebruik vir verwysingsdoeleindes. Die gesuiwerde AguA het die adsorpsie van arabinoglukuronoxilaan , wat vanuit bagasse, bamboes en P. patula ekstraheer is deur middel van die Hoije metode, op katoenlint die meeste laat toeneem in vergelyking met die effek van die rekombinante AbfB en die mengsel van die rekombinante AbfB en die gesuiwerde AguA. Die gesuiwerde AguA het die adsorpsie van die xilaan wat vanuit bagasse en E. grandis ekstraheer is met 334 en 29%, onderskeidelik, laat toeneem, maar het die adsorpsie van E. grandis xilaanjel en H2O2 gebleikte bagasse xilaan met 31 en 6%, onderskeidelik, laat afneem. Op ‘n soortgelyke wyse het die teenwoordigheid van die rekombinante AbfB die adsorpsie van die bamboes, P. Patula en hawer xilaan met 31, 44, en 900%, onderskeidelik, laat toeneem, maar die adsorpsie van die xilaan ekstraheer vanuit bagasse en die H2O2 gebleikte bagasse xilaan met 13 en 30%, onderskeidelik, laat afneem. Verskillende xilaan-sellulose interaksies en water adsorpsie kapasiteite van die katoen lint is opgemerk met die in situ modifikasie en adsorpsie van die xilaan ekstraheer vanuit die bagasse, bamboes, E. grandis en P. patula in die teenwoordigheid van die rekombinante AbfB en gesuiwerde AguA. Die ensiem bygestaande adsorpsie van xilaan kon daarom gebruik word om die funksionele eienskappe van die sellulose materiaal aan te pas of te verbeter. Die wekverrigting van ensimaties gevormde xilaan nanohidrojels as enkapsuleringmatrikse vir stadige vrystelling van bioaktiewe middels is geevalueer. Onoplosbare xilaan nanohidrojels wat gevorm is deur selektiewe verwydering van arabinose sykettings vanaf wateroplosbare hawer xilaan met die rekombinante AfbA, is gekarakteriseer vir partikelgrootteverspreiding, oppervlaklading (zeta potensiaal), morfologiese stabiliteit, en die vermoë om die ramenas peroksidase te enkapsuleer en stadig vry te stel. Die ensimaties gevormde hawer xilaan hidrojels het ‘n sferiese vorm gehad met partikelgroottes wat gewissel het van 18 nm tot > 10 000 nm. Die xilaan nanohidrojels het ‘n negatiewe zeta potensiaal van tot -19 mV getoon, en het self-vormings gedrag vir partikels ten toon gestel indien dit by xilaankonsentrasies hoër as 1.5% (m/v) en hidrolise tye langer as 17 h gevorm is. Die xilaan konsentrasie het beide die partikelgrootte en die zeta potensiaal van die hawerxilaan nanohidrojels beduidend (P < 0.05) beïnvloed terwyl die rekombinante AbfB hidrolise tyd beduidend (P < 0.05) was op die zeta potensiaal. Die hawer xilaan nanohidrojels, het die ramenasperoksidase ensiem suksesvol enkapsuleer, beide gedurende en na die vorming van die hawer xilaan nanohidrojels en die vrystelling van die geënkapsuleerde ramenas peroksidase in aktiewe vorm is volgehou vir ‘n periode van 180 min. Die ensieme wat die syketting van die xilaan verwyder het, het dus ‘n rol in die voorbereiding van biodegadeerbare nano-enkapsulasie geedskap. In die geheel veskaf die rekombinante AbfB en gesuiwerde AguA ‘n nuwe stel manier voor om wateroplosbare xilaan te funksionaliseer om as spesialiteit bymiddels, bedekking, en inplanting of enkapsulasiematrikse gebruik te word met ‘n verminderde impak op die omgewing. Dit sal prosessering bevorder en die produkspektrum van lignosellulose materiale uitbrei.

Up to 30% by mass of plant cell walls are comprised of hemicelluloses. The remainder is comprised of cellulose, lignin and extractives. Potential economic uses of hemicellulose include hydrogels, fibre additives in pulp mill paper-making and as a substrate for fermentation processes. Development of a fermentation process with sugars from hemicellulose has become of increasing interest due to their potential as a feedstock for fermentation-based liquid fuels and other bio-based chemicals. These can be incorporated into existing processes, in particular alkaline chemical pulping mills, where up to 50% of the hemicelluloses are today degraded and eventually combusted. The main objective of this project is to examine the solubility and aggregation properties of xylans (the predominant hemicellulose), as this will hopefully lead to better solubility-based separations for their recovery. This was done at Michigan State University by alkaline extraction at 85°C on milled birch wood, and at 130 and 170°C (both time-dependent) on birch chips, with 50 g/L sodium hydroxide. This was then followed by precipitation/aggregation experiments with ethanol, polyDADMAC (a polycationic flocculant) and by acidification. Characterisation was done by performing dynamic light scattering (DLS) and size exclusion chromatography (SEC) analysis on resolubilised recovered material from the different extraction conditions. From these, size distributions, molecular weights and degrees of polymerization (DP) could be estimated. The DP values for the extracted polymers were higher than the expected values for hardwood xylans, owing to the incoherent SEC chromatograms. This may be due to aggregate formation with other polymers or re-solubilisation issues of the hemicellulose precipitates. The estimated size range for model xylan was between 100 to 300 nm and the ethanol precipitates seemed to also lie around this region, as detected by DLS. One of the major factors contributing to the difficulty of analysing the results was the issue of re-solubilisation of the hemicellulose precipitates and flocculates. / <p>Validerat; 20120827 (anonymous); 2017-02-08 Nedladdad 414 gånger t.o.m. september 2016. Downloaded 414 times up until september 2016 (marisr)</p>

Kraft pulping, also known as sulphate pulping is a complex process where the wood components are liberated from each other facilitated by chemical reactions. During the pulping process some dissolved and degraded compounds end up together with the spent cooking chemicals in the black liquor. In kraft pulping of hardwood, the black liquor contains substantial amounts of dissolved hemicellulose, especially xylan due to the wood composition. The xylan content is of high value due to its ability to re-deposit by adsorption on cellulose fibres and its tendency to increase pulp strength and yield. In this work, the possibility of introducing xylan rich, hardwood black liquor from the hardwood digester into the softwood digester at the process of SCA – Munksund was studied. The objective was to investigate if hardwood black liquor addition in a softwood cook can increase the yield and pulp strength. The theoretical feasibility of altering the process was investigated by a literature review and a brief process investigation. During the study a total of eight lab cooks were conducted to obtain information on how hardwood black liquor addition changes the pulp quality of regular softwood cooks. The wood chips, white liquor and hardwood black liquor used were collected at Munksund and the process conditions in the lab cooks were chosen to simulate the actual process in the Munksund mill. In addition to the cooking, chemical and physical evaluation on pulps, cooking liquors and wood chips were performed. The theoretical evaluation indicates that the process in Munksund is well suited for introducing the hardwood black liquor in to the softwood digester. The chemical analysis of the black liquors show a xylan content that is approximately four times higher in the hardwood black liquor compared to the softwood black liquor. In the kappa number range of approximately 80-90, a total yield increase of 0.4%-units was obtained for two cooks with hardwood black liquor addition compared to their corresponding reference cooks. A carbohydrate analysis showed a higher xylan content in the pulp cooked with addition of hardwood black liquor compared to the corresponding reference pulp. One pulp with hardwood black liquor addition and its corresponding reference cook were refined in an Escher Wyss lab mill. The pulp with hardwood black liquor addition exhibits an increase or retained strength for all strength evaluation tests made on handmade pulp sheets. Strength increases of approximately 5% were obtained for tensile index and ISO-Z strength for a pulp with hardwood black liquor addition.   The results conducted in this study shows that it can be possible to slightly increase both the yield and some pulp strength parameters when adding hardwood black liquor in to the softwood cook in lab scale. It is also shown that the increase in the total yield most likely depends on xylan adsorption on the cellulose fibres. The calculated increased revenue for this process change could be over 400 000 Euro per year.