Intensification of the freeze-thaw pretreatment of disintegrated poplar wood
This research was focused on the effect of water content in the cells of disintegrated Populus nigra L. on a freeze-thaw pretreatment method before an enzymatic hydrolysis. Two chipped and sieved fractions 2.5 mm and 0.7 mm and two milled fractions, characterized as 18°SR (Shopper–Riegler index) and 37°SR, of the disintegrated 5 years old poplar tree were used for our experiment. Glucose and xylose yields were measured after 24 and 48 hours of enzymatic hydrolysis with a 15% load of the enzyme measured to a total cellulose content. The influence of nine freeze-thaw cycles under -20°C and +20°C was considered. The results showed that an increase in moisture content positively affects yields in all fractions but a desirable result was achieved mainly for the 0.7 mm fraction where the total yield increased by about 16%. More effective way is a finer wet beating of wood mass, while wood fibre receives moisture already in the technological process. The highest glucan conversion 51,74% and the total hemicelluloses conversion 47,72% was achieved for the finest fraction 37°SR. The higher moisture content has a positive effect on the increase in the conversion of oligosaccharides, especially glucan, in chipped fractions.