Modification of kraft pulp fibers by fungal pre-treatment of Iranian hornbeam chips

Industrial hornbeam chips were pre-treated by Trametes versicolor for 1, 2, and 3 wk, and after being well-washed by distilled water, were used for kraft pulping to achieve a kappa number of about 20. The kraft pulps from fungal pre-treated, reference and control samples, were analyzed by Bauer McNett classifier, Kajaani Fiberlab optical analyzer, and SEM. The results showed that the fungal pre-treatment can slightly degrade the lignin and carbohydrate structures of hornbeam chips after 3 wk, which affects kraft pulping and its fiber characteristics. The chemical charge in kraft pulping was similar for all of the samples. In comparison with the reference and control samples, a lower amount of fines and higher amount of long fiber fraction were observed in fiber classification for fungal pre-treated samples. Fiber properties such as fiber length, cross-sectional area, width, cell wall thickness, and volume index were slightly increased by increasing fungal pre-treatment time, while a slight reduction was observed in fines length, fiber coarseness, and fiber curl. Based on the findings of this study, a 3-wk T. versicolor pre-treatment was recommended to produce acceptable overall fiber properties in kraft pulping of hornbeam chips.

► We used Trametes versicolor for industrial hornbeam chips pre-treatment for fiber development of kraft pulp.
► Chips pre-treatment was done in 1, 2 and 3 weeks.
► 3 weeks fungal pre-treatment is recommended for producing acceptable overall fiber properties in kraft pulping of hornbeam chips.
► Since this fungus was not selective toward lignin degradation, degradation of carbohydrate structure would be unavoidable.