Monday, May 5, 2008
8-17

Enhanced enzymatic hydrolysis of rice straw biomass by an electron beam irradiation pretreatment process

Jin Seop Bak1, Ja Kyong Ko1, and Kyoung Heon Kim2. (1) Division of Food Bioscience and Technology, Korea University, College of Life Sciences and Biotechnology, Anam-dong, Seongbuk-gu, Seoul, South Korea, (2) School of Life Science & Biotechnology, Korea University, College of Life Sciences and Biotechnology, Anam-dong, Seongbuk-gu, Seoul, South Korea

The feasibility of using electron beam irradiation (EBI) as a pretreatment process to increase the enzymatic digestibility of lignocellulosic biomass by cellulose hydrolysis enzymes.  Depending on strength of the EBI, the pretreated rice straw by EBI demonstrated the different magnitudes physical and chemical changes.  In particular, the EBI pretreatment resulted in an increase of enzyme digestibility using cellulose hydrolysis enzymes (Trichoderma reesei cellulase and Aspersillus niger beta-glucosidase).  However, there was no significant change in the carbohydrate and lignin composition of the rice straw after the pretreatment by EBI.  The optimum EBI pretreatment condition (1 MeV-80 KGy) yielded 8.6 fold improvement in enzymatic digestibility compared to that of the control which was not pretreated at all.  The possible causes of the enhanced the enzyme digestibility were further investigated by using scanning electron microscope (SEM) and X-ray diffraction.  The relation between crystallinity index (CrI) and enzyme digetibility indicates strong correlation by giving an R2 value of 0.9052.  When certain EBI pretreatment conditions such as 1 MeV-92.4 KGy, 1.5 MeV-92.4 KGy and 2 MeV-92.4 KGy were excluded, the CrI and enzyme digestibility yielded a higher R2 value of 0.9555.  The three dimensional plot established by the relations of enzyme digestibility, electron beam energy, and irradiation dose successfully indicated the optimum ranges of EBI pretreatment conditions for achieving the maximum value of enzyme digestibility.


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