Study On Isolation,purification And Proliferation Activity Of Oligosaccharides From Yam

Dioscorea dioscorea is a homologous plant belonging to the genus Dioscorea in the family Dioscorea.Taking Chinese yam as raw material,the oligosaccharides were extracted,separated,purified and characterized,and the probiotic activity of Chinese yam oligosaccharides was explored.At the same time,the solid microcapsules of probiotics composed of them were studied.The main research results are as follows:1.By ultrasonic-assisted extraction method,polyamide and alcohol precipitation method were used to remove protein and polysaccharide.Three fractions were obtained by activated carbon column,and then three single fractions were obtained by LH-20 gel column,which were component one(Frl),component two(Fr2)and component three(Fr3).The results of infrared spectrum analysis showed that Frl and Fr2 were oligosaccharides with D-glucopyridinose,and Fr3 were oligosaccharides with D-glucopyranose.The molecular weights of the above three kinds of yam oligosaccharides were 0.74,0.95 and 1.25 kDa,respectively.Monosaccharide composition analysis showed that Frl and Fr2 were composed of glucose,galactose and mannose in different proportions,and Fr3 was composed of glucose,mannose,galactose and glucosamine.The Fr1 NMR results show that glucose and galactose exist in ?-configuration,mainly 1?6 linkage.By scanning electron microscope,it was found that the yam oligosaccharide showed a concave-convex structure with uneven surface.The structural formula of Frl was deduced as follows:mannose-?(1?6)glucose-?(1?4)galactose-?(1?6)glucose-?(1?6)glucose-glucose.The optimal structure of Frl was simulated by using COS software,and the possible active sites of Frl were discussed by using the advanced orbital theory.2.In the probiotic experiment,the OD600nm value of Bifidobacterium BB-12,Bifidobacterium bifidum bifidum and Lactobacillus reuteri were increased by 13.9%,8.24%and7.18%,respectively,compared with the xylo-oligosaccharide medium using yam oligosaccharide as carbon source.The three kinds of probiotics were further cultured with different components of yam oligosaccharide medium.The results showed that the experimental group was significantly higher than the sugar-free medium blank group(P<0.05),and the Fr1 and Fr2 groups were significantly higher than the sugar-free medium blank group(P<0.05).Meanwhile,the Frl and Fr2 groups had significant effects on the Fr3 group(P<0.05).In bifidobacterium bifidum BB-12 and bifidobacterium bifidum,there were differences between Frl and Fr2,but not significant(P>0.05).There was no significant difference between Frl group and Fr2 group in Lactobacillus reuteri(P>0.05).3.In the low temperature centrifugation experiment at 2×104 rpm for 15 min,for Bifidobacterium bifidum and Lactobacillus reuteri at the same concentration,the effect of yam oligosaccharide as a centrifugal protectant was better than that of fructose oligosaccharide and glucose,and the survival rates reached 82.34%and 79.82%,respectively.In the freeze-drying experiment,300g/L yam oligosaccharides had the best protective effect on bifidobacterium bifidum and bifidobacterium bifidum BB-12,and the survival rates reached 56.24%and 62.35%,respectively.4.In the beverage experiment,the probiotics capsules obtained by sharp space extrusion method had better particle shape,but larger volume;The microcapsules prepared by spray drying have good water solubility and are in the form of powder,but the temperature requirement is higher.After simulated gastric juice,bile juice and intestinal juice treatment,the number of BB-12 bifidobacterium microcapsules and BB-12 bifidobacterium naked bacteria decreased by 4.54 lg and 1.64 lg(CFU/mL),respectively.Meanwhile,at different storage temperatures,The preservation effect of microcapsules and naked bacteria powder at-20? was better than that at 4? and 20?,and the number of viable bacteria in microcapsules was significantly higher than that after activation of naked bacteria powder,which indicated that microencapsulation of probiotics could well reduce the death of bacterial strains and ensure the number of viable bacteria in products.