Investigation of biological pre-treatment of hornbeam wood with two white rot fungi and their effects on the optical and strength properties of CMP pulp

Today, due to environmental and economic reasons, the preparation of biomachanical pulps has expanded. In this study, hornbeam wood were exposed to two white rotting fungi, Pleurotus eryngii (King oyster) and lacteus Irpex (tooth)) from the forests of northern Iran for three weeks. They were cultivated according to the relevant standards. After three weeks, the chips were washed with cold water to remove fungal residues and after that, the chips air dried.Then, the chips were cooked with CMP process (temperature 170 C, L/W ratio5:1 and 90 minutes). 60 g/m2 handsheets were prepared from produced CMP pulps. and the optical and strength properties of pulp were investigated. The results showed that the strength properties of the resulting paper from Irpex lacteus mushroom pretreated hornbeam chips were higher than those of the treated with Pleurotus eryngii fungus Considering the optical properties of papers, it can be concluded that the opacity reduced beacuase of the more compact texture of the paper obtained from the treated wood chips and therefore the reduction of the light reflection inside the paper fiber network. The reason for the decrease in brightness after fungal treatments is the formation of chromosphere groups during the incubation and pulping period.

Based on the results, it became clear that the Irpex lacteus fungus in the period of destruction has acted like the white rot fungus, Pleurotus eryngii.It can be said that both fungi have the same destructive power and they destroyed the wood of the hornbeam about the same intensity.The average weight loss percentage of hornbeam sapwoods was 4.13% due to the destruction of Irpex lacteus and 3.95% by Pleurotus eryngii.The study and comparison of the mechanical strengths of the paper obtained from the attack of Irpex lacteus against Pleurotus eryngii showed the relatively different abilities of this fungus in association with the mechanical resistance of the resulting papers.The results of analysis of variance of the tensile index of paper prepared from sapwood of the hornbeam after 3 weeks of exposure to decaying white fungi showed that the rate of increase in tensile index by Irpex lacteus is about 9.6% more than Pleurotus eryngii .Also, the average percentage reduction in the tear index in paper prepared from sapwood of the hornbeam due to the destruction of Irpex lacteus was 14.2% lower than that of Pleurotus eryngii. The average percentage increase in the burst index of samples in paper prepared from sapwood of the hornbeam due to the destruction of Irpex lacteus was 5.74 more than that of Pleurotus eryngii. Considering the results related to the optical properties of the papers, it can be concluded that the opacity of paper obtained from the wood chips treated with Irpex lacteus decreased compared to Pleurotus eryngii, as well as the brightness of the paper from the wood treated with Irpex lacteus compared to Pleurotus eryngii has been further declined.The denser texture of the paper from the treated wood chips reduces the reflection of light inside the paper fiber network, which in turn reduces the opacity.The reason for the decrease in brightness after fungal treatments is the formation of chromophore groups during the incubation and pulping period. This indicates that the Irpex lacteus is more capable of reducing the opacityof the resulting paper than the Pleurotus eryngii.

The optical and strength properties of pulps have been investigated.Evaluations on the papers showed that the strength properties of the produced papers were higher after the Irpex lacteus pretreatment of the hornbeam chips with the Irpex lacteus over 3 weeks compared to that of pretretead with the Pleurotus eryngii .