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Chemical changes in thermomechanical pulp (TMP) from Norway spruce at alkaline conditions were examined at pH levels 9, 10, and 11, and temperatures of 40, 50, and 60°C. Alkali treatments were also made in the presence of hydrogen peroxide. The anionic charge of the fibres increased rapidly, following the kinetics of ester bond cleavage. Already at pH 9 and 60°C, acetic acid, methanol, pectic acids, and some lignin material were dissolved. Dissolution of xylans required higher pH. Lignin and xylans slowly leached into the water without affecting fibre charge. Leaching caused substantial material loss during extended alkali treatment. At pH 11, hydrogen peroxide almost doubled the overall loss of wood material compared with alkali only. This was partly due to acceleration of the dissolution of xylans and lignin material, but also due to considerable formation of low-molar-mass oxidation products. The effect of hydrogen peroxide on fibre charge was considerable also during extended treatment. [ABSTRACT FROM AUTHOR]

The degradation of dissolved and colloidal substances from thermomechanical pulp (TMP) by bacteria isolated from a paper mill was studiedin a laboratory slide culture system. Burkholderia cepacia strains hydrolysed triglycerides to free fatty acids, and the liberated unsaturated fatty acids were then degraded to some extent. Saturated fatty acids were not notably degraded. However, the branched anteiso-heptadecanoic fatty acid was degraded almost like the unsaturated fatty acids. About 30% of the steryl esters were degraded during 11 days, increasing the concentrations of free sterols. Approximately 25% of the dehydroabietic, and 45% of the abietic and isopimaric resin acids weredegraded during 11 days. The degree of unsaturation seemed to be of greater importance for the degradation of fatty acids than the molar mass. No degradation of dissolved hemicelluloses could be observed with any of the nine bacterial strains studied. Burkholderia cepacia strains and one Bacillus coagulans strain degraded monomeric fructose and glucose in winter TMP water, but in summer TMP water, with much lower sugar concentrations, also other Bacillus strains degraded monomeric sugars. [ABSTRACT FROM AUTHOR]