Transformation of oil palm fronds into pentose sugars using copper (II) sulfate pentahydrate with the assistance of chemical additive

Among the chemical pretreatments available for pretreating biomass, the inorganic salt is considered to be a relatively new but simple reagent that offers comparable pentose (C5) sugar recoveries as the conventional dilute acid hydrolysis. This study investigated the effects of different concentrations (1.5-6.0% (v/v)) of H2O2 or Na2S2O8 in facilitating CuSO4·5H2O pretreatment for improving pentose sugar recovery from oil palm fronds. The best result was observed when 0.2 mol/L of CuSO4·5H2O was integrated with 4.5% (v/v) of Na2S2O8 to recover 8.2 and 0.9 g/L of monomeric xylose and arabinose, respectively in the liquid fraction. On the other hand, an addition of 1.5% (v/v) of H2O2 yielded approximately 74% lesser total pentose sugars as compared to using 4.5% (v/v) Na2S2O8. By using CuSO4·5H2O alone (control), only 0.8 and 1.0 g/L xylose and arabinose, respectively could be achieved. The results mirrored the importance of using chemical additives together with the inorganic salt pretreatment of oil palm fronds. Thus, an addition of 4.5% (v/v) of Na2S2O8 during CuSO4·5H2O pretreatment of oil palm fronds at 120 °C and 30 min was able to attain a total pentose sugar yield up to ∼40%.