Effect of Ultrasound-Assisted on Sequential Peracetic Acid and Alkaline Peroxide Pretreatment to The Enzymatic Hydrolysis of Oil Palm Empty Fruit Bunch

Abstract

Enzymatic hydrolysis of oil palm empty fruit bunch (OPEFB) that has been pretreated by modified pretreatment has been investigated in this study. The OPEFB used was pretreated by using sequential peracetic acid – alkaline peroxide solution. As the modification method, the assistance of pretreatment by ultrasound was conducted, in order to increase the enzyme accessibility. Therefore, it enhances the production of reducing sugar on the hydrolysis process. Prior to hydrolysis process, OPEFB was initially treated by using peracetic acid solution, comprise of CH3COOH (> 99%) and H2O2 (30% w/w), assisted by ultrasound for 3 hours at 35oC. Afterwards, OPEFB was treated by using alkaline peroxide solution, comprise of NaOH (40% w/w) and H2O2 (35% w/w), assisted by ultrasound for 10 hours at 35oC. OPEFB that has been pretreated was then subjected to enzymatic hydrolysis process using cellulase enzyme, in order to convert cellulose content into reducing sugar. Enzymatic hydrolysis was carried out at 50oC in a shaker incubator with 150 rpm for 48 hours. In this study, the effect of different enzyme concentration and hydrolysis time towards the sugar concentration in modified-pretreated OPEFB was observed and analyzed. Three different concentrations of enzyme were used, including 1.25, 2.5, and 5 g/L, and reducing sugar concentrations were analyzed at 30 and 45 minutes, and 1, 2, 4, 6, 24, 30, and 48 hours. Based on results, enzyme concentration has a significant effect to the production of reducing sugar. The reducing sugar concentrations obtained at the end of the hydrolysis process were 8.48, 11.06, 19.16 g/L, at the enzyme concentrations of 1.25, 2.5, and 5 g/L, respectively. At any hydrolysis time, the highest sugar concentration has been achieved on the highest enzyme concentration of 5 g/L. Moreover, the effective hydrolysis time were achieved at 6 hours, at all concentration of enzyme, since the production of reducing sugar were insignificant after 6 hours. This study showed an increase in reducing sugar production by 8.25% in the hydrolysis process using OPEFB pretreated by modified pretreatment compared to the non-modified pretreatment.