NR 06. Sugar production from rice straw

Abstract

The objective of this work was to assess the utility of the Ammonia Pressurization and Depressurization (PDA) process to enhance the enzymatic production of reducing sugars from rice straw (RS). Two experiments were carried out in duplicate. The first experiment involved a 20 min-treatment time and three moisture levels (15, 35 and 60 %). In the second experiment, three treatment times (0, 6 and 20 min) were tested with 35 % moisture-samples. NDF, ADF and ADL were determined in quadruplicate in the samples to estimate solubles, cellulose, hemicellulose and lignin. Samples were subjected to enzymatic hydrolysis by cellulase, cellobiase and hemicellulase (5 IU/g DM, 28.4 CBU/g and 2.5 mg/g, respectively). The ammonia treatment significantly increased solubles content of rice straw (P<.001), mainly with moisture content (up to 47.17 %). Moisture appears to help the ammonia penetrate the biomass for reaction. Sugar production increased significantly (P<.001) for PDA-treated samples compared to the control, and was greater with higher moisture contents and increased times. The best PDA condition, 60 % moisture content for a 20 min treatment, increased the sugar yield by 6.5 times to 67 % of theoretical. The high increase in sugar yield reflects the effect of the ammonia treatment on increasing the susceptibility of cellulose and hemicellulose to enzymatic hydrolysis. PDA treated RS provides an alternative source of sugars for animal feeding and may replace starch in appropriate applications.