Production of novel sugars by microbial fermentation

我们正在研究无乳链球菌荚膜多糖的生物合成，它具有唾液酸乳糖胺聚合物。唾液酸刘易斯糖是一种肿瘤特异性抗原。我们正试图通过重组DNA技术生产这些有用的糖，为此，我们试图提高糖的生产水平。我们已经分离出了一个基因簇，它包含了编码糖合成基因的多个基因。其中，cpsIaR基因与其他糖合成基因一起导入大肠杆菌。重组大肠杆菌具有较高的酶活。在25%蔗糖的高渗条件下，CpsIaR和其他糖合成酶的水平也有所提高。我们还分析了CpsIaJ的底物特异性，CpsIaJ被鉴定为β-1-4-半乳糖基转移酶。我们发现该酶可以将半乳糖基转移到人工受体和GlcNAc Gal Glc三糖上。

We are studying biosynthesis of the capsular polysaccharide of Streptococcus agalactiae, which has sialyl lactosamine polymer. Sialyl Lewis sugar was known as a tumor specific antigen. We are trying to produce these kinds of useful sugar by recombinant DNA technology.For this purpose, we tried to increase the production level of the sugar. We have already isolated a gene cluster, which contain multigenes those encoding sugar synthesis genes. Among them, cpsIaR gene was introduced in Escherichia coli with other sugar synthesis genes. This recombinant E.coli showed higher enzyme activity. Under high osmorality with 25% sucrose, both CpsIaR and other sugar biosynthesis enzymes level also increased. Together, these results suggest that CpsIaR positively regulates sugar biosynthesis.We also analyzed the substrate specificity of CpsIaJ which was identified as a β-1-4-galactosyl transferase. We found that the enzyme could transfer galactosyl moiety to both artificial acceptor and GlcNAc-Gal-Glc trisaccharide.