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Research On The Efficient Mechanism For Degrading Cellulose In The Rumen Of Luxi-Cattle

Posted on:2012-05-09Degree:MasterType:Thesis
Country:ChinaCandidate:J L WangFull Text:PDF
GTID:2210330338961761Subject:Biochemistry and Molecular Biology
Abstract/Summary:PDF Full Text Request
The development and utilization of biomass energy is currently a hot issue which attracted universal attention from all over the world. Rumen of the ruminant animal (such as cattle) is one of the most highly efficient natural systems for cellulose degradation. Luxi-Cattle, an excellent species for animal husbandry in Shandong Province, has strong ability in digesting the roughage (such as hay and straw). In-depth study of the mechanism of Luxi-Cattle rumen's high efficiency in degrading cellulose may provide new insight into the achievement of the large-scale industrialization of biomass energy.In this study, we found that the rumen fluid of Luxi-cattle has the ability to degrade hemicellulose, free cellulose and crystalline cellulose, and its cellulase activity is higher than that of the crude enzyme system of Trichoderma pseudokoningii S38. The endoglucanses of the rumen fluid show optimal CMCase activity at a neutral pH around 6.0 and 50℃, and the hemicellulases of the rumen fluid show optimal xylanase activity at a neutral pH around 5.0 and 45℃. Through Native-PAGE improved, we further found that there are at least 10 xylanases,12 endoglucanses,1 exoglucanase and 2β-glucosidases components in rumen fluid. Through the observation of the ultrastructure of cellulose substrates (such as CF11 cellulose powder) degraded in situ in rumen, we discoved that some grooves appear on the surface of CF11 cellulose powder and some holes appear on the bottom of these grooves. The width of the grooves in the surface of CF11 cellulose powder is approximately equal to the diameter of Ruminococcus flavefaciens in the rumen.After the preliminary separation from the chyme of rumen, using the character that cellulases can strongly bind to cellulose substrates and the technology of molecular sieve column chromatography, we isolated a component with high molecular weight, high mass to charge ratio and variety of glycoside hydrolase activity. All these properties were very similar to that of the cellulosome produced by anaerobic bacteria reported before. However, when separated from the bacteria, the concentration liquid of cellulosomes displayed a relatively low degradation ability for the crystalline cellulose substrates (such as CF11 cellulose powder and filter paper), despite it shows high enzyme activity for carboxymethyl cellulose-sodium. Besides, there is no groove and hole observed on the surface of the substrates.Based on these results, we consider the rumen of Luxi-cattle can efficiently degrade natural cellulose substrates with high crystallinity. We predicted that the efficient mechanism mainly depended on the variety of glycoside hydrolase produced by their symbiotic anaerobic microbes in the rumen, especially the cellulosomes produced by Ruminococcus. Through a way of rolling movement, together with the cellulosomes binding to its surface, Ruminococcus is able to break down the crystalline structure of cellulose, and then gradually degrade the natural cellulose substrate. The Ruminococcus-cellulosome complex may be a prerequisite to degrade crystalline cellulose. The cellulosome will lose most of its ability in degrading natural crystalline cellulose when separated from bacteria.
Keywords/Search Tags:Cellulosome, Rumen, Luxi-Cattle, Ultrastructure, Cellulase
PDF Full Text Request
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