Effect Of White-rot Fungus Pretreatment To Populus Xiaohei On Bio-chemical Pulping

White-rot fungus and poplar were selected as materials in this paper. Culture and screening of white-rot fungus were done. Differences of Laccase activity production of white-rot fungus were analyzed and screened. Fungus producing Laccase were picked out. So, the suitable method of white-rot fungus culture was found. And then, the better white-rot fungus was inculcated on the poplar. Chemical properties and fiber figure of poplar before and after fungus pretreatment were analyzed. The most suitable white-rot fungus and time for the next bio-chemical pulping were probed. In these conditions, the poplar was made pulping, and the kappa number, the pulp yield, residual alkalis and viscosity of the pulp before and after fungus pretreatment were measured, and then the paper was made, finally physics indexes of the paper were determined. Study results were as follows:1. Through solid culture and by the method of Bavendamm, the amount of Laccase activity was took as screening fungus strains that could produce Laccase. In the end, Phlebia radiate, Polystictus versicolor, Coriolus versicolor, Pleurotus streatus, Pleurotus florida, and Lentinus edodes were progressively choosed out. But there was no demonstration of laccase of Schizophyllum commune. Then the amount of producing Laccase activity of different carbon source, nitrogen source, and pH value of the liquid medium were contrasted, and finally found out the better of them were the glucose, the protein peptone, and and5.0, respectively. The best formulas of white-rot fungus accordingly composed of potatoes 200g/L, glucose 20g/L, and protein peptone 5g/L, agar 15-20 g/L, KH₂PO₄ 3.0g/L, MgSO₄·7H₂O1.5g/L and VB₁ 0.01g/l, After the liquid medium and solid medium were compared, and the actual situation was considered, so, finally the potato synthesis culture medium for culturing fungus was determined for the next poplar pretreatment.2.During the entire processing, the level of lignin degradation of different fungus strains from high to low were: Lentinus edodes, Coriolus versicolor, Polystictus ersicolor, Phlebia radiate, Pleurotus florida, and Pleurotus streatus. The holocellulose degeneration of Lentinus edodes was the highest, next were Phlebia radiate, Lentinus edodes, Pleurotus florida, Pleurotus streatus and Polystictus versicolor. After Polystictus versicolor pretreatment, the average pentose content was to be the highest, next were Coriolus versicolor, Pleurotus streatus, Polystictus versicolor, Pleurotus florida, and Lentinus edodes. 1%NaOH extractives was the highest after Polystictus versicolor pretreatment, others from high to low were Coriolus versicolor, Phlebia radiate pleurotus florida, Lentinus edodes, and Pleurotus streatus. Ashes contents from high to low were Coriolus versicolor, Polystictus versicolor, Phlebia radiate, Pleurotus streatus, Pleurotus florida, and Lentinus edodes. Changes of chemical compositions were gentle from 0 to 20 days, fiercest from 20 to 30 days, and gradually enlarged from 30 to 50 days. In line with the least processing time , the holocellulose degradation was lower, and the lignin degradation rate was higher, so , Polystictus versicolor, Phlebia radiata, Lentinus edodes, and Pleurotus florida were took as fungus strains for the biological pretreatment,30 days was the best pretreatment time.3. After pretreatment, the range of the average fiber length degradation of Phlebia radiate, Pleurotus streatus, and Pleurotus florida were higher than Polystictus versicolor, Coriolus versicolor, and Lentinus edodes. The fiber length to width were all improved after fungus pretreatment, and changes of them from 0 days to 20 days, from 20 days to 40 days and from 40 days to 50 days were closer, different, and consistent, respectively. During the entire time, after fungus pretreatment, the lumen diameter was increased, and the double wall thickness and the ratio of the double wall thickness to lumen diameter were decreased.As the principle of the average fiber length was longer, the fiber length to width was bigger, and the ratio of the double wall thickness to the lumen diameter was smaller. Polystictus versicolor, Phlebia radiate, Lentinus edodes, Pleurotus florida were selected as the next fungus for bio-pulping, and 30 days was the best processing time.4. Orthogonal experiments results showed the best condition of pulping was:alkali quantity, sulfidity, fluid ratio, the maximum temperature, and the holding time were 16%, 24%, 1:4.5,165℃, and 60minutes, respectively.5. Compared to the control sample, results of bio-pulping showed:(1) After Phlebia radiata, Polystictus versicolor, and Pleurotus florida pretreatment, the kappa number was decreased, the pulp yield , viscosity and delignification selectivity were increased;(2) After Lentinus edodes pretreatment, the kappa number and delignification selectivity were increased and decreased, respectively, but the pulp yield and viscosity decreased.6. After dealing by white-rot fungus, the beating degree was higher than the comparison sample, which would do good to energy conservation in the same conditions.7. Physical properties of the paper was measured, compared to control sample, indexes of tensile strength and the tear ability were improved after Phlebia radiate, Polystictus versicolor and Pleurotus florida pretreatment. But indexes of tensile strength and tear ability were reduced after by Lentinus edodes pretreatment. After the four white-rot fungus pretreatment, the folding endurance and brightness were increased.