The nitric acid pretreatment on palm oil mill effluent (POME) to enhance reducing sugar production

Abstract

Nitric acid pretreatment can improve the reducing sugar (RS) recovery by converting the hemicellulose contained in cellulosic materials. The RS is containing functional groups capable of being digested in the subsequent process, such as fermentation. In this study, nitric acid (HNO3) pretreatment was performed on palm oil mill effluent (POME) under the range of reaction time from 5 to 30 minutes, reaction temperature from 25 to 70°C, and HNO3 concentration from 0.1 to 3% w/v to determine the reducing sugar content measured by using Dinitrosalicyclic Acid (DNS) method. The Box-Behnken Design (BBD) based on Response Surface Method (RSM) was performed to determine the optimal conditions of 9.9 minutes, 65.56 °C, and 2.04% w/v HNO3 concentration. Under these conditions, 2031.73 mg/L reducing sugar was recovered, a value close to the predicted result calculated by the model. The reducing sugar recovery was improved by 13% compared to the untreated POME. Hence, the study established the importance of statistical tools to enhance the reducing sugar output, increasing the energy conversion efficiency of the industrial wastes