Effects of pretreatment conditions and post-pretreatment washing on ethanol production from dilute acid pretreated rice straw

Rice straw pretreatment was examined in a full factorial study at temperatures of 120 degrees C and 160 degrees C and 0% and 1% [H2SO4]. Pretreatment efficacy was assessed by measuring hydrolysate composition and reducing sugar yield after enzymatic hydrolysis. Pretreatment with 1% [H2SO4] and 160 degrees C yielded the highest amount of reducing sugar, 259 mg g(-1) [dry matter], during enzymatic hydrolysis corresponding to 57% glucose conversion based on cellulose content of the pretreated solid. Under this pretreatment condition hydroxymethylfurfural and furfural were 0.19 and 0.68 g l(-1), respectively. Rice straw pretreated with 1% [H2SO4] at 160 degrees C was subjected to simultaneous saccharification and fermentation (SSF) using either Saccharomyces cerevisiae D(5)A or recombinant Escherichia coli KO11. Solid and hydrolysate separation and washing techniques were evaluated for their effect on ethanol production during SSF. Pretreated rice straw without liquid-solid separation or washing had the highest 7-d ethanol yield of 0.2 g [ethanol] g(-1) [dry substrate] for E. coli KO11. This finding has economic implications on the processing of rice straw to bioethanol. (C) 2015 IAgrE. Published by Elsevier Ltd. All rights reserved.