Tuesday, April 20, 2010
8-82

Enzymatic saccharification of rice straw pretreated using TiO2/UV for bioconversion to ethanol

Hee-Kyoung Kang1, Nahyun M. Kim2, Ghahyun Kim3, Hyun-Jung Kim4, Donal F. Day5, Jongho Kim1, and Doman Kim6. (1) The Research Institute for Catalysis, Chonnam National University, 300 Yongbong-dong, Gwangju, 500-757, South Korea, (2) Korean Minjok Leadership Academy, HeungoSeung Gun, Kangwon-do, 225-823, South Korea, (3) Department of Biology, UCSD, La Jolla, CA 92092, (4) Home School, Bundang-gu, Seongnam, South Korea, (5) Audubon Sugar Institute, LSU Agricultural Center, 3845 Hwy 75, St Gabriel, LA 70776, (6) School of Biological Sciences and Technology, Interdisciplinary Program of Graduate School for Bioenergy & Biomaterials, Chonnam National University, 300 Yongbong-dong, Gwangju, 500-757, South Korea

Rice straw is a lignocellulosic biomass that is a renewable organic substance and alternative source of energy. Presently, rice straw was pretreated in a novel manner using TiO2/UV system and the pretreated rice straw was hydrolyzed using Accellerase 1000™. Hydroxyl radicals (OH·) can degrade lignin and carbohydrates. UV irradiation of TiO2 solution, hydroxyl radicals producing system, was investigated for its ability to oxidize rice straw. The optimal conditions for TiO2/UV pretreatment were found to be: TiO2 concentration (0.1%, w/v), irradiation time (120 min), UV lamp type (UVC, 254 nm). Under these conditions, the cellulose saccharification was 346.68 mg glucose/g rice straw (81.41% of theoretical) and hemicelluloses saccharification was 55.08 mg xylose/g rice straw (25.91% of theoretical). These results show that UV irradiation of the TiO2 solution is an efficient pretreatment method to enhance rice straw digestibility. The fermentation of enzymatic hydrolysates containing 10.5 g/L glucose and 3.21 g/L xylose with Pichia stipitis produced 3.94 g/L ethanol with corresponding yield of 0.39 g/g rice straw. Also, the final ethanol concentration was about 1.37%, which is 75.1% of the stoichiometric and fermentation efficiency yields. For the first time, TiO2/UV system was developed for the pretreatment for saccharification of lignocelluloses. It is a potential pretreatment method for enabling ethanol production from lignocelluloses.

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