Degradation of the Lignocellulose by Using Clostridium xylanolyticum, a Symbiotic Bacterium in the Termite Gut
Date Issued
2009
Date
2009
Author(s)
Wu, Wei-Ching
Abstract
It was found that the symbiotic microorganisms in termite gut can digest lignocellulose, i.e., to degrade the cellulose and hemicellulose into short-chain oligosaccharides. In this study, Clostridium xylanolyticum, a symbiotic bacterium in termite gut has been used to degrade the lignocellulose. At the beginning, Congo red dye assay was applied to identify its capability in degradation of sodium carboxymethyl cellulose (CMC-Na) and xylan, and then cultivated with the modified peptone–yeast extract-glucose (PYG) medium. The major fermentation products are formate, acetate and ethanol. The accumulation of acetate will result in the decrease of pH, and a significant antiproliferative effect will occur when the ambient pH is lower than 5.0. The growth curve for this particular bacterium showed a 12 hrs lag phase, an 18 hrs exponential growth phase, and followed consequently the stationary phase. The mean generation time was found to be 2.4 hrs, and the optimal inoculation time was between 24-30 hrs. o evaluate its degradation ability about the cellulose and hemicellulose, experiments using different substrates such as glucose, cellobiose, sodium carboxymethyl cellulose, microcrystalline cellulose Avicel® PH-101, xylose, and xylan were conducted. The results showed Clostridium xylanolyticum had preference in degradation of xylan. Therefore, xylan was then selected as the substrate for acclimation of the inoculum. During acclimation, the ability of xylan degradation and acid resistance were significantly improved. In follow-up substrate fermentation experiment, the first subculture was used as the inoculum for its superiority in xylan degradation and could be reacted rapidly after one day of inoculation.n fermentation experiment of the annual Ma Bamboo, its sugar content was rapidly consumed at beginning 24 hrs, and large amount of acids, alcohol, hydrogen and carbon dioxide were produced with pH under control. Most hemicellulose in Ma Bamboo were almost completely used in this experiment, and 4.85 g/L of acetate, 0.14 g/L of alcohol, 99.3 mL of hydrogen and 179.6 mL of carbon dioxide were produced. Among these products, the acetate can be used as the substrate for methane fermentation, while hydrogen and alcohol can be used as the gaseous and liquid fuel, respectively.
Subjects
xylan
Ma Bamboo
Type
thesis
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