Efficient of Acid Hydrolysis of Oil Palm Empty Fruit Bunch Residues for Xylose and Highly Digestible Cellulose Pulp Productions

Acid hydrolysis of oil palm empty fruit bunches was developed to produce xylose in liquid solution and cellulose pulps in solid residues. The residual cellulose pulps were further investigated for their enzymatic digestibility. The effecting factors including substrate loading (5–25% w/v), sulfuric acid concentration (0.5–7.5% v/v) and hydrolysis time (30–90 min) were optimized employing response surface methodology. Enzymatic digestibility of residual cellulose pulps was evaluated in the condition consisting of 1% w/v substrate loading, 20 FPU/g cellulose pulp for cellulase from Trichoderma reesei and, 4 U/g cellulose pulp for cellobiase from Aspergillus niger by operating for 2 days at 50 °C with 160 rpm shaking. The maximum xylose production of 48.25 g/L with xylose yield of 57.50% were carried out at 24.81% substrate loading, 4.78% acid concentration and 73.89 min hydrolysis time. On the other hand, at lower acid concentration of 3.77% and a shorter hydrolysis time of 68.97 min achieved of 96.49% xylose yield with 22.56 g/L xylose production. In addition, increasing of acid concentration and hydrolysis time was highly affected on furfural and HMF liberations. The highest furfural concentration was 2.22 following 1.66 and 1.54 g/L with acid concentration (6–7.5% (v/v) for 60–75 min while HMF was the highest at 1.92 g/L following 1.86 and 1.53 g/L with acid concentration of 4–7.5% (v/v) for 60–75 min. For enzyme digestibility condition of cellulose pulps, the results indicated that glucose production and glucose yield were related to substrate loading concentration and increasing of hydrolysis time could enhanced glucose yield. The highest enzyme digestibility was 32.30% with the highest glucose production and glucose yield of 3.23 g/L and 6.14%, respectively which were carried out at 10% (w/v) substrate loading, 2% (v/v) acid concentration and 75 min hydrolysis time.