| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 97 === A cellulolytic bacterial strain was isolated from soil taken from southern Taiwan and identified as Acinetobacter junii F6-02 via phylogenetic and 16S rRNA sequencing analysis. Investigation of cellulases and xylanase production of Acinetobacter junii F6-02 showed that the activity of those cellulolytic enzymes were mainly located extracellularly. The optimal temperature and pH for xylanase activity 60oC and 7, respectively, while the best condition for xylanase production by A. junii F6-02 was 35oC, and 0.3 vvm aeration speed was the best xylanase production condition. The best carbon source concentration and nitrogen source to optimize xylanase production was 5 g/L each for CMC and xylan and peptone 1 g/L. Lyophilized enzyme bioagent produced from Acinetobacter junii displays better xylanase ability than supernatant of the fermentation broth. The enzyme bioagent displayed a stable long-term hydrolysis at a temperature of 50oC. Xylanase purification via FPLC shows that two xylanase enzymes exist in the supernatant of Acinetobacter junii and their molecular weight is about 70 and 85 kDa. The vmax and Km of xylanase with the substrate of xylan and NaOH pretreated straw was 8.6 g/L/h, 10.6 g/L and 3.6 g/L/h, 26.9 g/L, respectively. Batch H2 fermentation with Clostridium butyricum CGS5 shows that using hydrolysate of xylan and NaOH pretreated rice straw as the substrate, the maximum H2 production rate was 62.5 and 26.8 ml/h/L, respectively, and maximum H2 yield were 0.70 and 0.76 mol H2/mol xylose, respectively. Simultaneous enzymatic xylan saccharification and hydrogen fermentation was also investigated. Under a reaction temperature of 37oC, the hydrogen production rate reached a maximum value of 35.3 ml/h/L, which is markedly lower than that obtained from the two-stage process.
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