Characterization of an acidotolerant，thermophilic Thermoanaerobacter sp．xyl-d with a high xylose conversion

Abstract:

Abstract:［Objective］We screened a thermophilic xylolytic bacterium that produced fuel ethanol from a high-temperature oil reservoir，and provided microbial resources to genetic engineering strains construction and consolidated bioprocessing．［Methods］We adopted Hungate anaerobic technique to isolate strain xyl-d from oil reservoir water sample enriched for two years from Shengli Oilfield in China，and we identified strain xyl-d with morphological，physiological，biochemical and phylogenetic analysis．［Results］ Strain xyl-d was gram-negative，rod-shaped，spore-forming and strictly anaerobic．The growth temperature ranged from 30℃ to 85℃ (optimum 65℃) and the pH ranged from 3.0 to 10.0 (optimum 7.5) and salt concentration was 0%－4%(optimum at 2.0%)．It converted D-xylose into ethanol，acetate，CO2，trace amount of iso-butanol and propionate． The genomic DNA G + C contents of strain xyl-d was 45. 6 mol% ． Based on 16S rRNA gene sequence，strain xyl-d was most close to Thermoanaerobacter wiegelii DSM10319T and Thermoanaerobacter ethanolicus DSM 2246T both with the 99. 3% similarity． It produced more ethanol and less acetate at initial pH 8. 5 than other pH． Ethanol yield was increased significantly with yeast extract，and ethanol became the main end product． In addition，growth of strain xyl-d was inhibited obviously with ethanol concentration more than 7% (V/V)．In the optimum growth conditions，xylose degradation rates reached to 91.37%．［Conclusion］ Strain xyl-d was thermophilic，high xylose conversion rate，acidotolerant anaerobe． It was a potential bacterium that can be used for consolidated bioprocessing．