Different pulps were chemically (nitren) and biologically (enzyme) treated in order to improve the chemical accessibility and dissolution capacity in cold NaOH. The treatments effect on the pulp properties was accessed by studying the changes on their chemical and macromolecular structure and by analyzing the dissolution performance in cold NaOH.The nitren treatment has the effect of removing a large part of the xylan present in a dissolving pulp and is also removing mannans. Increasing the nitren concentrations will extract also cellulose and decrease its mean molar mass. These extractions are favorable for the dissolution in cold NaOH–water, being more effective with higher nitren concentrations. A maximum of 44.7% increase on the dissolution yield was achieved.The new enzymatic treatment shows a higher efficiency on promoting fibers accessibility to NaOH ions, (directly correlated with the enzymatic load), allowing a maximum increase of 150% on the dissolution yield. A slight decrease of the average molar mass was also seen. The different pulps reacted differently to the treatments, showing that the pulping pretreatments have an influence on the enzymatic efficiency. Using a mixture of enzymes and endoglucanase showed that the synergistic effect of these two enzymes is more effective on cellulose activation.Both nitren and enzymatic treatments are improving the pulp chemical accessibility mostly by modifying the structure of the primary wall and S1 wall. This promotes the swelling of these wood cell structures, allowing the access of the NaOH solvating ions into fiber regions not accessible on the original pulp. The nitren is disassembling the fiber surface with extraction of hemicelluloses and degrading the cellulosic structure.The use of this enzyme on the cellulose pulps activation towards dissolution in cold NaOH is of great importance. It presents a high potential in both technical, with further development and industrial implementation, and fundamental research fields, with further studies on mechanisms of cellulose activation.The work was performed in Cemef - Mines ParisTech, Sophia Antipolis, France, and TI / Hamburg University, Germany and financed by Sappi, Tembec, Lenzing, Viskase and Spontex and had support from EPNOE (European Polysaccharide Network of Excellence). / Different pulps were chemically (nitren) and biologically (enzyme) treated in order to improve the chemical accessibility and dissolution capacity in cold NaOH. The treatments effect on the pulp properties was accessed by studying the changes on their chemical and macromolecular structure and by analyzing the dissolution performance in cold NaOH.The nitren treatment has the effect of removing a large part of the xylan present in a dissolving pulp and is also removing mannans. Increasing the nitren concentrations will extract also cellulose and decrease its mean molar mass. These extractions are favorable for the dissolution in cold NaOH–water, being more effective with higher nitren concentrations. A maximum of 44.7% increase on the dissolution yield was achieved.The new enzymatic treatment shows a higher efficiency on promoting fibers accessibility to NaOH ions, (directly correlated with the enzymatic load), allowing a maximum increase of 150% on the dissolution yield. A slight decrease of the average molar mass was also seen. The different pulps reacted differently to the treatments, showing that the pulping pretreatments have an influence on the enzymatic efficiency. Using a mixture of enzymes and endoglucanase showed that the synergistic effect of these two enzymes is more effective on cellulose activation.Both nitren and enzymatic treatments are improving the pulp chemical accessibility mostly by modifying the structure of the primary wall and S1 wall. This promotes the swelling of these wood cell structures, allowing the access of the NaOH solvating ions into fiber regions not accessible on the original pulp. The nitren is disassembling the fiber surface with extraction of hemicelluloses and degrading the cellulosic structure.The use of this enzyme on the cellulose pulps activation towards dissolution in cold NaOH is of great importance. It presents a high potential in both technical, with further development and industrial implementation, and fundamental research fields, with further studies on mechanisms of cellulose activation.The work was performed in Cemef - Mines ParisTech, Sophia Antipolis, France, and TI / Hamburg University, Germany and financed by Sappi, Tembec, Lenzing, Viskase and Spontex and had support from EPNOE (European Polysaccharide Network of Excellence).

In the forest products industry the opportunity exists to extract currently under-utilised compounds from the process or waste streams and thereby derive more value from the wood entering the process. A big portion of the hemicellulose content of wood does not form part of the final product. Extracting the hemicelluloses from the waste streams or other locations in the process would allow them to be used more effectively. The predominant hardwood hemicellulose, xylan, is polymeric xylose. Xylose is an important platform sugar in bioconversion strategies and can be converted to fuels and other valuable chemicals. The xylan polymer can be hydrolysed to its xylose monomers by a number of conversion strategies; the most widely known being chemical and enzymatic digestion. Chemical conversion is usually done using acid at elevated temperatures, but high yields are often offset by degradation of the product. On the other hand, enzymatic hydrolysis can be better regulated to prevent unwanted degradation of the monomeric sugar products. Enzymatic hydrolysis has been pronounced the environmentally friendly choice of technology, although it is hampered by low conversions and high cost of enzymes. To date commercial enzymes for biomass conversion are not readily available most of which are still in development. In understanding how to best utilise a xylan, recovered from the pulping process, the potential to convert hardwood xylan to xylose with enzymes currently available on the market was studied. A hardwood xylan extracted from fully bleached Eucalyptus pulp with a chelating agent, Nitren, was used as substrate to evaluate the ability of some commercial enzymes to degrade the extracted xylan to xylose monomers. The enzymes used in this study were not dedicated biomass conversion enzymes, but rather chosen for their xylan degrading potential, i.e. xylanase content. By means of hydrolysis profiles on commercial Birchwood and Oat Spelts xylan as substrates and enzyme characterisation, Multifect xylanase was identified as most promising enzyme for xylan conversion. Multifect contained high levels of xylanase and xylosidase activity in the enzyme preparation. Commercial Birchwood xylan and the extracted Eucalyptus xylan were found to be chemically similar, both composed predominantly of xylose. The hydrolysis profiles obtained on Birchwood xylan could therefore serve as a benchmark against which the hy-drolysis of Eucaluptus xylan could be compared. Full conversion of the Eucalyptus xylan with Multifect could not be achieved, although Multifect completely degraded the Birchwood xylan. The maximum xylose yield that could be obtained on Eucalyptus xylan was 80 % and it was concluded that the remaining 20% was unhydrolysable by the enzyme, most likely due to the limitations in the employed extraction method. It was however noted that up to the point of 80 % conversion higher hydrolysis rates were observed on Eucalyptus xylan than Birchwood xylan with equal charges of Multifect. The differences in hydrolysis rates may have indicated that the Eucalyptus xylan is more accessible to enzyme attack than the Birchwood xylan, likely as a result of the extraction methods used to prepare the xylans. A simple economic evaluation illustrated the weight of various costs in process profitability. The most economic operation of a continuous steady state reactor is at a low enzyme charge, 17 IU/ℓ, and a long retention period, five days, due to the high cost of the enzyme compared to other factors. For a reduced retention time, an investigation into enzyme immobilisation and the use of a packed-bed type reactor is recommended. / Dissertation (MEng)--University of Pretoria, 2009. / Chemical Engineering / unrestricted

Different pulps were chemically (nitren) and biologically (enzyme) treated in order to improve the chemical accessibility and dissolution capacity in cold NaOH. The treatments effect on the pulp properties was accessed by studying the changes on their chemical and macromolecular structure and by analyzing the dissolution performance in cold NaOH.The nitren treatment has the effect of removing a large part of the xylan present in a dissolving pulp and is also removing mannans. Increasing the nitren concentrations will extract also cellulose and decrease its mean molar mass. These extractions are favorable for the dissolution in cold NaOH-water, being more effective with higher nitren concentrations. A maximum of 44.7% increase on the dissolution yield was achieved.The new enzymatic treatment shows a higher efficiency on promoting fibers accessibility to NaOH ions, (directly correlated with the enzymatic load), allowing a maximum increase of 150% on the dissolution yield. A slight decrease of the average molar mass was also seen. The different pulps reacted differently to the treatments, showing that the pulping pretreatments have an influence on the enzymatic efficiency. Using a mixture of enzymes and endoglucanase showed that the synergistic effect of these two enzymes is more effective on cellulose activation.Both nitren and enzymatic treatments are improving the pulp chemical accessibility mostly by modifying the structure of the primary wall and S1 wall. This promotes the swelling of these wood cell structures, allowing the access of the NaOH solvating ions into fiber regions not accessible on the original pulp. The nitren is disassembling the fiber surface with extraction of hemicelluloses and degrading the cellulosic structure.The use of this enzyme on the cellulose pulps activation towards dissolution in cold NaOH is of great importance. It presents a high potential in both technical, with further development and industrial implementation, and fundamental research fields, with further studies on mechanisms of cellulose activation.The work was performed in Cemef - Mines ParisTech, Sophia Antipolis, France, and TI / Hamburg University, Germany and financed by Sappi, Tembec, Lenzing, Viskase and Spontex and had support from EPNOE (European Polysaccharide Network of Excellence).