Study On Enzymolysis Of Rapeseed Polysaccharides And Prebiotic Activity Of Rapeseed Polysaccharides Enzymatic Derivatives

In this paper, the enzymolysis technology of extacted and purified rapeseed polysaccharides (RP-1 and RP-2) was investigated, and the chemical compositions and primary structures of rapeseed polysaccharides and their enzymatic derivatives (DRP-1 and DRP-2) were characterized. Furthermore, the proliferative effect of the RP-1, RP-2, DRP-1 and DRP-2 on probiotics in vitro was also studied. Finally, the effects of RP-1, RP-2, DRP-1 and DRP-2 on short chain fatty acids produced by fermentation were studied. The main contents and results are as follows:1. Study on the optimal enzymolysis conditions of rapeseed polysaccharides. Cellulase was selected to be the optimal tool enzyme. Single-factor experiments and orthogonal test were carefully designed to determine the optimal enzymolysis condition of rapeseed polysaccharides. The optimal condition for enzymolysis were obtained as cellulase concentration of 150 U/mL, reaction temperature of 50℃, and pH value of 5. The products of the enzymatic hydrolysis were purified with Sephadex G-50 column chromatography, and two enzymatic derivatives were obtained which were designated as DRP-1 and DRP-2, respectively.2. Study on the chemical compositions and structures of the rapeseed polysaccharides and their enzymatic derivatives. HPLC analysis showed that RP-1、DRP-1、RP-2 and DRP-2 were homogeneous, and molecular weights were 52485,7184,11908, and 5526 Da, respectively. The UV analysis revealed that no nucleic acid was found in polysaccharides and enzymatic derivatives. It also indicated that RP-1 and RP-2 contained protein in their structers, but DRP-1 and DRP-2 did not. The gas chromatography analysis showed that RP-1, RP-2, DRP-1 and DRP-2 were composed of rhamose, arabinose, xylose, mannose, glucose and galactose. Results showed that the molar ratios of total sugar, protein, uronic acid and sulfate in RP-1 were 68.23,13.26, 8.85 and 9.66%, respectively. Whereas, they were calculated to be 65.84,19.10,4.90and 10.16%, respectively, in RP-2. The molar ratios of total sugar, uronic acid and sulfate in DRP-1 were 81.40,6.38 and 12.22%, respectively. The molar ratios of these species were of 78.43,10.20, and 11.37%, respectively, in DRP-2.3. Study on the proliferative effect of the rapeseed polysaccharides and enzymatic derivatives on probiotics. The proliferative experiments of four selected probiotics (Bifidobacterium adolescentis, Bifidobacterium infantis, Bifidobacterium bifidum and Lactobacillus acidophilus) were conducted in vitro, and the effects were estimated according to the changes of OD and pH value of the cultivated media. The results showed that all RP-1, RP-2, DRP-1 and DRP-2 can stimulate the proliferation of the probiotics significantly. However, enzymatic derivatives showed better proliferation effects than rapeseed polysaccharides. The appropriate concentration of RP-1, RP-2, DRP-1 and DRP-2 for probiotics was 1.5-2.0%. Furthermore, the pH values of the media decreased during the cultivation, and greater decreases were found in the media containing DRP-1 and DRP-2. The results indicated that the RP-1, RP-2, DRP-1 and DRP-2 can be utilized by probiotics and produce SCFA. The growth curves of the tested strains showed that the probiotics reached plateau phase after 24-32 h cultivation when supplemented with the RP-1 and RP-2, but the plateau phase occurred after 16-24 h cultivation when supplemented with DRP-1 and DRP-2, indicating that the enzymatic derivatives had better proliferative effect on probiotics than rapeseed polysaccharides.4. Study on the effect of rapeseed polysaccharides and enzymatic derivatives on short chain fatty acid products fermented by probiotics. When adding RP-1, RP-2, DRP-1 and DRP-2 into the cultivation media respectively, four kinds of short chain fatty acid namely, acetate, propionate, butyrate and lactate, mostly acetate, can be produced by fermentation of Bifidobacterium adolescentis, Bifidobacterium infantis and Bifidobacterium bifidum. As for the products fermented by Lactobacillus acidophilus, acetate, propionate and lactate, mostly lactate, can be detected in the media. In addition, the enzymatic derivatives showed better promotion in production of acetate, propionate, butyrate and lactate than rapeseed polysaccharides, which indicated that the rapeseed polysaccharide enzymatic derivatives had better proliferation effect on probiotics than rapeseed polysaccharides.