Abstract
BackgroundUse of lignocellulosic biomass has received attention lately because it can be converted into various versatile chemical compounds by biological processes. In this study, a two-step pretreatment with dilute sulfuric acid and aqueous ammonia was performed efficiently on rice straw to obtain fermentable sugar. The soaking in aqueous ammonia process was also optimized by a statistical method.ResultsResponse surface methodology was employed. The determination coefficient (R2) value was found to be 0.9607 and the coefficient of variance was 6.77. The optimal pretreatment conditions were a temperature of 42.75°C, an aqueous ammonia concentration of 20.93%, and a reaction time of 48 h. The optimal enzyme concentration for saccharification was 30 filter paper units. The crystallinity index was approximately 60.23% and the Fourier transform infrared results showed the distinct peaks of glucan. Ethanol production using Saccharomyces cerevisiae K35 was performed to verify whether the glucose saccharified from rice straw was fermentable.ConclusionsThe combined pretreatment using dilute sulfuric acid and aqueous ammonia on rice straw efficiently yielded fermentable sugar and achieved almost the same crystallinity index as that of α-cellulose.
Highlights
Use of lignocellulosic biomass has received attention lately because it can be converted into various versatile chemical compounds by biological processes
The rice straw that had been subjected to dilute-acid pretreatments to remove a large portion of amorphous hemicellulose was pretreated again with aqueous ammonia to remove lignin
Response surface methodology analysis Rice straw was pretreated with dilute sulfuric acid under previously optimized conditions: 142°C temperature, 1.21% concentration of sulfuric acid, and 11.6 min reaction time [11]
Summary
The combined pretreatment using dilute sulfuric acid and aqueous ammonia on rice straw efficiently yielded fermentable sugar and achieved almost the same crystallinity index as that of α-cellulose.
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