Competitive inhibition of cellobiohydrolase I by manno-oligosaccharides |
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| Institution: | 1. College of Forestry, Northwest A&F University, 3 Taicheng Road, Yangling 712100, China;2. Department of Food and Environmental Sciences, University of Helsinki, P.O. Box 27, FIN 00014 Helsinki, Finland;1. Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan;2. Biomass Engineering Program, RIKEN, 1-7-22, Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan;3. Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada, Kobe 657-8501, Japan;4. Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan;5. Center for Future Chemistry, Kyushu University, Fukuoka 819-0388, Japan;1. Department of Microbiology, Guru Nanak Dev University, Amritsar 143005, Punjab, India;2. Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, India;3. Centre for Structural and Functional Genomics, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec H4B 1R6, Canada;1. State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, Shandong, China;2. Advanced Research Center for Optics, Shandong University, Qingdao, Shandong, China |
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| Abstract: | In the hydrolysis of softwood, significant amounts of manno-oligosaccharides (MOS) are released from mannan, the major hemicelluloses in softwood. However, the impact of MOS on the performance of cellulases is not yet clear. In this work, the effect of mannan and MOS in cellulose hydrolysis by cellulases, especially cellobiohydrolase I (CBHI) from Thermoascus aurantiacus (Ta Cel7A), was studied. The glucose yield of Avicel decreased with an increasing amount of added mannan. Commercial cellulases contained mannan hydrolysing enzymes, and β-glucosidase played an important role in mannan hydrolysis. Addition of 10 mg/ml mannan reduced the glucose yield of Avicel (at 20 g/l) from 40.1 to 24.3%. No inhibition of β-glucosidase by mannan was observed. The negative effects of mannan and MOS on the hydrolytic action of cellulases indicated that the inhibitory effect was at least partly attributed to the inhibition of Ta Cel7A (CBHI), but not on β-glucosidase. Kinetic experiments showed that MOS were competitive inhibitors of the CBHI from T. aurantiacus, and mannobiose had a stronger inhibitory effect on CBHI than mannotriose or mannotetraose. For efficient hydrolysis of softwood, it was necessary to add supplementary enzymes to hydrolyze both mannan and MOS to less inhibitory product, mannose. |
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| Keywords: | Cellobiohydrolase Inhibition Mannan Manno-oligosaccharides Enzymatic hydrolysis |
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