3. Results and discussion
3.1. Effect of different pretreatment on OPEFB digestibility
Untreated OPEFB has digestibility of only 3.4%, fungal pretreatment
improved the digestibility to 15.4%, which is 4.5 times higher
than the untreated. As the fungus primarily deligninfies lignocelluloses,
this improvement could most likely related to the reduction
of the lignin by fungal pretreatment. Phosphoric acid pretreatment
significantly increased the digestibility to 81.4% and combined pretreatment
resulted in 56.1% digestibility. It means the acid could
improve the digestibility by 24.0 times. Digestibility of combined
pretreatment was increased 16.5 times. Phosphoric acid pretreatment
shows highest improvement of digestibility and could be related
to the reduction of the crystallinity of OPEFB cellulose, this
corresponds with earlier report about phosphoric acid pretreatment
reducing the crystallinity of cellulose (Jeihanipour et al.,
2010)