Bingbing Xia,Zhiwei Li,Jinao Wei,Ganpeng Hu,Jingwen Yang,Hongbin Zhang,Xueqin Hu
Dextranases are hydrolases that exclusively catalyze the disruption of α−1,6 glycosidic bonds . A series of variant enzymes were obtained by comparing the sequences of dextranases from different sources and introducing sequence substitutions. A correlation was found between the number of amino acids in the 397–401 region and the hydrolytic process. When there were no more than 5 amino acids in the 397–401 region, the enzyme first hydrolyzed the dextran T70 to a low molecular weight dextran with a molecular weight of about 5000, then IMOs 1 appeared in the system if the degradation continued, showing a clear sequential relationship. And when there are more than 5 amino acids in the 397–401 region, IMOs were produced at the beginning of hydrolysis and continue to increase throughout the hydrolytic process. At the same time, we investigated the enzymatic properties of the variants and found that the hydrolytic rate of A-Ca was 11 times higher than that of the original enzyme. The proportion of IMOs produced by A-Ca was 80.68%, which was nearly10% higher than the original enzyme, providing a new enzyme for the industrial preparation of IMOs.
Li Zhou,Fenglu Han,Kunyu Lu,Yanbing Qiao,Erchao Li
Prebiotic fermentation by gut microbiota is a key foundation for prebiotics exhibiting physiological functions. However, the relationship among prebiotic type, gut microbiota and gut microbiota metabolism remains unclear. In this study, the gut microbiota of shrimp ( Litopenaeus vannamei ) was inoculated into medium containing 1% fructooligosaccharide (FOS), galactooligosaccharide (GOS), mannanoligosaccharide (MOS), inulin, β-glucan, isomaltooligosaccharide (IMO) and xylooligosaccharide (XOS). The pH value, digestive enzyme activity, short-chain fatty acid yield and gut microbiota in the fermentation liquid were evaluated. The results showed that after 12 h of in vitro fermentation, β-glucan exhibited the lowest pH value and highest amylase activity among the other types of prebiotics. β-glucan had a higher ability to produce short-chain fatty acids (SCFA) and inhibit the formation of branched-chain fatty acids (BCFA) than the other types of prebiotics. At the genus level, β-glucan markedly promoted the growth of Bacillus . These findings suggest that β-glucan was the most suitable type of prebiotic and had greater prebiotic effects than the other types of prebiotics on the basis of in vitro fermentation by the gut microbiota of shrimp ( Litopenaeus vannamei ).
危险品化学品经营许可证（带存储）