Optimization of enzymatic saccharification of steam pretreated rice biomass using OFAT method

Abstract

Rice biomass is one of the most abundant agricultural residue after harvesting of paddy rice in Malaysia. The potential of rice biomass which is rich of lignocellulosic material was investigated to synthesize fermentable sugars. In this study, rice biomass was selected to undergo enzymatic saccharification to produce fermentable sugars. Rice husk and rice straw with ratio of 1:3 was pretreated using steam pretreatment at 210 ºC and 10 minutes in order to degrade hemicellulose and to reduce lignin content of rice biomass. Weight loss of rice biomass was calculated after pretreatment. Characteristics of untreated and pretreated rice biomass had been observed by Scanning Electron Microscopy (SEM), and changes of functional groups were determined by Fourier Transform Infrared Spectroscopy (FTIR). Three parameters including enzyme concentration (1.5, 2.0 and 2.5 % v/v), pH (5.0, 5.5 and 6.0) and incubation time (24, 48 and 72 hours) were optimized during enzymatic saccharification using One-Factor-at-A Time Method (OFAT). Average weight loss content of rice biomass of 53.73% was achieved during steam pretreatment. SEM showed that the chemical structure of untreated rice biomass had been disrupted and altered from highly order and linear morphology to cracking and higher porosity during steam pretreatment. For FTIR, the peaks of Si-O-Si bonds, C=C stretching of lignin aromatic ring and H-C-H stretching vibration of methyl and methylene portions of cellulose were eliminated. The optimum condition for enzymatic saccharification was at 2.5 % (v/v) enzyme concentration, pH 5.0 and 72 h incubation time. Average reducing sugars concentration of 4.715 mg/ml was obtained in the experiment.