Enhancement of fermentable sugars production from oil palm empty fruit bunch by ligninolytic enzymes mediator system

• Enzymatic pretreatment for OPEFB were investigated.
• Enzymatic pretreatment using ligninolytic enzyme-mediator systems were developed.
• Laccase and MnP enzyme mediator were combined in one pretreatment system.
• Ligninolytic enzymes with HBT + Mn(II) enhanced fermentable sugars production.

The impact of crude ligninolytic enzyme-mediator pretreatment on the bio-modification and partial removal of oil palm empty fruit bunch (OPEFB) lignin prior to cellulose hydrolysis was evaluated. The OPEFB was first treated with ligninolytic enzyme together with mediators and then hydrolysed with commercial cellulase for its fermentable sugars production. Two mediators of laccase, hydroxybenzotriazole (HBT) and azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) were compared in the pretreatment of OPEFB whereas manganese sulphate was used as mediator for manganese peroxidase (MnP). Optimum pretreatment conditions with maximum Klason lignin removal were achieved at concentration of 1.5% HBT, 4 mM ABTS and 2 mM manganese (II) with as much as 8.02%, 8.68% and 3.7% respectively as compared to raw OPEFB. lignin was removed from OPEFB by 8.8% at 50 °C and 8.16% at 10% of substrate loading, respectively. Pretreatment verifications at optimal condition was determined by cellulose hydrolysis of pre-treated OPEFB from the combination of HBT-Mn (II) and ABTS-Mn (II) which increased sugar yield by 16%–17% with approximately 30 g/L of fermentable sugars as compared to crude ligninolytic alone with 19.1 g/L, suggesting that mediators had played important roles in modification and partial removal of lignin, thus improved cellulose accessibility.