Steam Explosion of the Softwood Pinus Radiata with Sulphur Dioxide Addition. II. Process Characterisation

Abstract The enzymatic digestibility of the softwood Pinus radiata is substantially enhanced by SO2-catalysed steam explosion. The factors controlling the effectiveness of this pretreatment have been studied. Under conditions of constant time (3 minutes) and temperature (215°c) the effects of SO2-impregnation levels from 0–11.8% were examined. Up to about 3% SO2 there is a pronounced effect on the enzymatic digestibility of the pretreated substrate and a rapid increase in the yield of water soluble sugars. At 2.55% SO2, a total sugar yield of 57.4 g/100 g oven-dry wood was obtained. SO2 levels above 3% had no beneficial effects in terms of increased sugar yields. Equivalent total sugar yields could be obtained by shortening the treatment time to 1 minute and increasing the temperature to 235°c (still at 2.55% SO2). Percentage solubilisation of wood glucan correlates strongly with the enzymatic digestibility of the pretreated substrate and also with the surface area accessible to a 51A molecule. This sugge...

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