Jiaxun Feng

Guangxi University, Yung-ning, Guangxi Zhuangzu Zizhiqu, China

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Publications (2)0 Total impact

  • Li Liu · Jiliang Tang · Jiaxun Feng
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    ABSTRACT: To analyze the diversity of bacterial community in Guangxi buffalo rumen and to identify the possible cellulolytic bacterial group. Metagenomic DNAs were isolated directly from a buffalo rumen and its enriched culture, and were used as PCR templates to amplify 16S rRNA genes. Two libraries carrying 16S rRNA genes of bacteria in the two samples were constructed. The bacterial community composition was revealed by the constructed phylogenetic tree of known sequences and the sequences randomly selected from the libraries. We found that both samples contained low G + C Gram-positive bacteria (LGCGPB) and Cytophaga-Flexibacter-Bacteroides (CFB) phyla as the majorities, and Spirochaetes as the minorities. LGCGPB accounts for 56.66% and 73.33% of the bacterial communities in buffalo rumen and its enriched culture. We detected Fibrobacteres in the rumen sample (3.33%) but not in the enriched sample. Furthermore, we found Proteobacteria as a major component in the enrichment (13.33%) but not in the rumen sample. Clone R46 was not clustered into any known phyla and might belong to a novel taxonomic group. The LGCGPB and Proteobacteria may play important roles in the hydrolysis of cellulose in buffalo rumen. The bacterial composition in the rumen of buffalo is quite similar to those in the rumen of yak, cattle and sheep.
    No preview · Article · Mar 2009 · ACTA MICROBIOLOGICA SINICA
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    ABSTRACT: Metagenomic cosmid libraries containing 1.26 x 10(5) clones, covering about 4.8 x 10(6) kb metagenomic DNA of uncultured microorganisms from the contents of buffalo rumens were constructed, and 118 independent clones expressing beta-glucosidase activity were isolated from the libraries. Screening of these clones showed that eight clones expressed relatively higher beta-glucosidase activity at pH 5.0 and 37 degrees C. One out of the eight clones was subcloned. Sequencing analysis showed that an open reading frame (ORF) of 2223 bp, termed umcel3G, potentially encodes a beta-glucosidase. The encoded product shared highest homology with a beta-glucosidase from Bacillus sp. at 60% identity and 73% similarity. The umcel3G was over-expressed in Escherichia coli and the size of the translated product Umcel3G on SDS-PAGE was in agreement with the predicted molecular mass. Zymogram analysis showed that Umcel3G exhibited beta-glucosidase activity, confirming that this ORF encodes a beta-glucosidase. The Umcel3G, purified with Ni-NTA column, exhibited optimal activity at pH 6.0-6.5 and 45 degrees C. Certain ions such as Ca2+, Zn2+ had significant positive effect on the activity of Umcel3G. However, some ions such as Fe3+, Cu2+ gave significant inhibitory effect on the enzyme. The Ni-NTA purified recombinant beta-glucosidase Umcel3G had a specific activity of 22.8 IU/mg at pH4.5, 35 degrees C and at the presence of 5 mmol/L Ca2+, indicating that this enzyme has potential applications in the fermentative production of ethanol by simultaneous saccharification and cofermentation (SSCF) of lignocelluloses.
    No preview · Article · Mar 2008 · Sheng wu gong cheng xue bao = Chinese journal of biotechnology