The utilization of hemicellulases in bleaching of kraft (sulphate) pulp is considered as one of the most important new large‐scale industrial applications of enzymes. This is partly due to the great potential of an environmentally safe method. This method has in a short period also proven to be economically realistic. The main enzymes needed in the enzyme‐aided bleaching have been shown to belong to the group of endo‐/gb‐xylanases. Xylanases act mainly on the relocated, reprecipitated xylan on the surface of the pulp fibres. Enzymatic hydrolysis of this specific type of xylan renders the structure of the fibres more permeable. The hydrolysis of xylan or mannan in the inner fibre layers may also enhance the bleachability. In practical process conditions, properties of the enzymes such as substrate specificity and the pH and temperature optima are of utmost importance. The benefits obtained by enzymes are dependent on the chemical bleaching sequence used as well as on the residual lignin content of pulp. The main goals in the enzyme‐aided bleaching of kraft pulps have been the reduction of consumption of chlorine chemicals in the bleaching process and consequently lowering the AOX of the effluents. Enzymes have been applied as a pretreatment both in conventional (C/D)EDED and in ECF (elementary chlorine‐free) bleaching sequences. In the production of TCF (totally chlorine‐free) pulps, enzymes have also been successfully used for increasing the brightness of pulp.

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Birch wood chips, with or without peroxyacetic acid pretreatment, were subjected to steam explosion treatment at 160, 220 and 250 °C for different periods of time to reach the same severity or P-factor values (1000, 15,000 and 96,000 min) at each temperature. The exploded pulp was subsequently extracted with water and a 0.4% alkali solution. The alkali soluble fraction was studied by means of elemental, methoxyl analysis, conductometric titration, 'H-, quantitative 13 C-NMR and FTIR spectroscopy, and gel permeation chromatography methods. With an increasing P-factor value, the polysaccharide content of the alkali soluble fraction decreases rapidly, the syringylpropane unit and aliphatic OH-group concentration decreases, the phenolic OH-group concentration increases, lignin side chains are subjected to oxidation and partial destruction, and pseudolignin is incorporated into lignin macromolecules. The increase in temperature at equal severity of steam explosion has some effect on the removal of the syringylpropane units and on pseudolignin formation. Peroxyacetic acid pretreatment does not have a pronounced effect on the structure of alkali soluble compounds.

Optimization of assay conditions for serum alanine aminotransferase (ALAT, GPT) and aspartate aminotransferase (ASAT, GOT) are described for English sole, Parophrys vetulus. Although most conditions for measurement of these fish enzymes parallel conditions in mammals, the optimal pH is lower for both these enzymes. Liver represents a potentially large source of ASAT activity, potential sources for ALAT activity are liver and kidney. As in mammals, the use of these enzymes as indicators of fish liver and kidney dysfunction may be warranted.

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