The rough crystal of exopolysaccharide produced by Enterococcus durans, a strain of lactic acid bacteria screened from the intestine of a cock in our laboratory, was purified by CM-cellulose column chromatography, DEA...The rough crystal of exopolysaccharide produced by Enterococcus durans, a strain of lactic acid bacteria screened from the intestine of a cock in our laboratory, was purified by CM-cellulose column chromatography, DEAE-Sephadex A-25 ionexchange and Sephadex G-100 gel chromatography to give EPS-Ⅰ. The EPS-Ⅰ was eluted as a single peak in HPLC analysis, indicating the homogeneity of EPS-Ⅰ and free from low-molecular-weight polysaccharides. The molecular weight of the EPS-Ⅰ was determined as 42 000 by the light scattering method. The result of its elemental analysis was C 41.08% and H 7.23% without the elements of N, P and S. Monosaccharide analysis showed that it was composed of Glc and Man in a molar ratio of 4∶1. Sugar composition analysis, methylation analysis and 1H and 13C NMR spectroscopy revealed that the EPS-Ⅰ was composed of pentasaccharide repeating units. The sequence of sugar residues was determined by using two-dimensional NMR, including heteronuclear multiple-bond correlation(HMBC) and nuclear overhauser effect spectroscopy(NOESY). The structure of the pentasaccharide repeating unit of EPS-Ⅰ was given, a new excellular polysaccharide from lactic acid bacterium compared with other EPSs was reported.展开更多
利用接合转移的方法将不同来源的二型硫酯酶(TEII,type II thioesterase)导入链霉菌S.avermitilis NRRL8165中构建了两种突变株,同时研究比较了两种突变株与野生型在等量发酵时阿维菌素产量的变化。结果表明:导入Tetrocarcin A的TEII突...利用接合转移的方法将不同来源的二型硫酯酶(TEII,type II thioesterase)导入链霉菌S.avermitilis NRRL8165中构建了两种突变株,同时研究比较了两种突变株与野生型在等量发酵时阿维菌素产量的变化。结果表明:导入Tetrocarcin A的TEII突变株阿维菌素的产量提高了96.52%;导入氯丝菌素(Chlorothricin)的TEII突变株阿维菌素的产量提高了38.06%。进一步验证了TEII对聚酮类次级代谢产物的生物合成具有编辑和纠错功能。展开更多
基金the Ministry of Science and Technology(200007801),the National Natural Science Foundation of China(20321202,90206005,20372080,20332040,20425208),and the Chinese Academy of Sciences.
文摘The rough crystal of exopolysaccharide produced by Enterococcus durans, a strain of lactic acid bacteria screened from the intestine of a cock in our laboratory, was purified by CM-cellulose column chromatography, DEAE-Sephadex A-25 ionexchange and Sephadex G-100 gel chromatography to give EPS-Ⅰ. The EPS-Ⅰ was eluted as a single peak in HPLC analysis, indicating the homogeneity of EPS-Ⅰ and free from low-molecular-weight polysaccharides. The molecular weight of the EPS-Ⅰ was determined as 42 000 by the light scattering method. The result of its elemental analysis was C 41.08% and H 7.23% without the elements of N, P and S. Monosaccharide analysis showed that it was composed of Glc and Man in a molar ratio of 4∶1. Sugar composition analysis, methylation analysis and 1H and 13C NMR spectroscopy revealed that the EPS-Ⅰ was composed of pentasaccharide repeating units. The sequence of sugar residues was determined by using two-dimensional NMR, including heteronuclear multiple-bond correlation(HMBC) and nuclear overhauser effect spectroscopy(NOESY). The structure of the pentasaccharide repeating unit of EPS-Ⅰ was given, a new excellular polysaccharide from lactic acid bacterium compared with other EPSs was reported.
文摘利用接合转移的方法将不同来源的二型硫酯酶(TEII,type II thioesterase)导入链霉菌S.avermitilis NRRL8165中构建了两种突变株,同时研究比较了两种突变株与野生型在等量发酵时阿维菌素产量的变化。结果表明:导入Tetrocarcin A的TEII突变株阿维菌素的产量提高了96.52%;导入氯丝菌素(Chlorothricin)的TEII突变株阿维菌素的产量提高了38.06%。进一步验证了TEII对聚酮类次级代谢产物的生物合成具有编辑和纠错功能。
