Monosaccharides such as glucose, xylose and arabinose are the main monomer units of which cellulose and hemicelluloses are composed. The cellulose and hemicelluloses content in many biomass species makes them suitable for 2G bioethanol production. Today, when 1G bioethanol production is closely monitored due to its enormous consumption of food raw materials such as wheat or corn grains, larger companies are gradually moving to pilot operations of 2G bioethanol production. However, cellulose and hemicelluloses contained in biomass are only very slightly accessible to enzymes used in 2G bioethanol production. Therefore pretreatment methods such as steam explosion are very suitable to use for fractionation of cell structure. In this paper, we tested the cellulose accessibility. We compared the cellulose accessibility of wheat straw particles with wooden particles obtained from beech and poplar. Particle size was less than 0.7 mm. We identified the optimal conditions of steam explosion pretreatment at reaction temperature of 200 °C for wheat straw, poplar and beech wood particles. The main indicator of accessibility was concentration of monomers obtained from enzymatic hydrolysis. The concentration of monomer was determined by high performance liquid chromatography. The experimental results showed different accessibility measure for each type of biomass species.
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.
The effect of steam explosion on enzymatic hydrolysis of various parts of poplar tree (heartwood, sapwood and 1-year coppice) was investigated. These parts were milled, the obtained sawdust was chemically analysed and then steam explosion of 0.7 mm poplar particles at temperature of 205°C was performed. Concentration of monomers obtained after enzymatic hydrolysis was considered as the main indicator for cellulose accessibility. Analysis of high performance liquid chromatography showed that non-treated poplar sawdust does not enable sufficient cellulose accessibility, while excessively high temperature and rapid pressure release resulted in substantial breakdown of polysaccharides and lignin and formation of inhibitors. The concentration of monomers increased gradually in the order of coppice, sapwood and heartwood. Steam exploded heartwood gave the maximum monosaccharides concentration of 90.0 g. L-1 after 72 hours of enzymatic hydrolysis. However, glucose concentration culminated after 48 hours of this hydrolysis. This corresponds to the best holocellulose accessibility for enzymes. The maximum concentration of inhibitors (9.3 g. L-1) was determined for poplar coppice after 24 hours of enzymatic hydrolysis.
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