Enhance Enzymatic Digestibility of Rice Straw by Ammonia Modification Process at Ambient Condition

Abstract

As a lignocellulosic biomass material, rice straw consists of cellulose, hemicelluloses, and lignin. Lignin might cover cellulose and hemicelluloses from chemical or biological treatment. Therefore, delignification process is needed to remove lignin from lignocellulosic biomass structures and increase the productivity of cellulose and hemicelluloses conversion. Many researchers were trying to have a better method for delignification by using many chemical in various conditions, such as sulphuric acid, NaOH, Ca(OH)2, NH4OH, NMMO, etc. In this study, delignification was carried out in mixture solution from ammonia and sodium hydroxide at ambient temperature for various time of pretreatment (0.5, 1, 2, 5, 24, 48 hrs, 7 and 14 days). Rice straw is mainly consisting of 33 wt% cellulose, 26 wt% hemicelluloses, and 18 wt% lignin, respectively. The results indicate that about 90 wt% lignin was removed with the mix solution in 24 hrs, compared to 28% with water, 55% with sodium hydroxide and 69% with ammonia only. As a linier correlation, the sodium hydroxide and ammonia mixture solution shown the better result also for enzymatic digestibility compare to use them separately.