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The article presents results of the elimination of sticky impurities from recovered paper in laboratory flotation of three pulp suspensions with different whiteness, obtained directly from the production line before entering flotation. A combination of commercial agents releasing undesirable substances from recovered paper and means for regulation and stabilization of froth and modified micronized bentonit was used. In the flotation purification of pulp suspension with a whiteness of 53%, the combination of Prodeink Extra, Prodeink AS10 and Hydrocol OT reduced the macrostickies content by 58%, the ash content decreased from 18.5% to 4.5%, the whiteness increased from 53% to 56.4% and the residual color content was reduced from 385 ppm to 294 ppm. The pulp suspension with a whiteness of 64% showed a reduction in the content of macrostickies by 66%, a reduction in the ash content by 23.2%, an increase in whiteness by 1.4% and a reduction in the residual color content from 245 ppm to 194 ppm. The pulp suspension with a whiteness of 68.3% showed a decrease in the content of macrostickies by 58.1%, the ash content decreased from 35.7% to 6.3%, the whiteness increased by 1.1% and the content of residual color decreased from 157 ppm to 117 ppm.

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The publication is focused on the effect of ultra low and high temperature on enzymatic pretreatment of beech wood (Fagus sylvaticaL.). Two fractions < 0.7 mm and 1.0 –2.5 mm of disintegrated branches sawdust were used for experiments. Glucose and xylose yields were measured after 24, 48, and 72 hours of enzymatic hydrolysis with 15 % load of the enzyme measured to total cellulose content. The influence of freezing under -80°C and boiling under pressure at +160°C on samples before enzymatic hydrolysis was observed. Mutual combination of boiling under pressure to obtain the maximum water uptake and subsequent freezing was used to better understand the process of cell destruction. The results show that the boiling pretreatment has a positive influence on thetotal monosaccharide yields and the subsequent freezing may slightly increase these yields even further. The maximum monosaccharide conversion (73.24%) was achieved using the fraction < 0.7 mm.