Ultrasonic Synergistic Preparation Of Polysaccharides From Lotus Seeds And Its Effect On The Proliferation Of Lactobacillus

(1)Ultrasonic microwave assisted preparation(UMAP)of polysaccharides from lotus seed were studied.The effects of ultrasonic power,microwave power,ratio of water volume to raw material weight(W/M ratio)and extraction time on the yield of lotus seed polysaccharides(LSPs)were investigated respectively.On the basis of these single factor experiments,the extraction technology of LSPs extracted by UMAP was optimized by response surface methodology.The results showed that the optimum technology conditions were as follows:ultrasonic power of 110 W,microwave power of 110 W,W/M ratio of 55 mL/g and extraction time of 70s.Under these conditions,the yield of polysaccharides could be up to(9.78±10.02)%,which was consistent with the theoretical value.Comparing with the traditional hot water extraction(HWE),ultrasonic-assisted extraction(UAE),it increased by 20.31%and 482.14%respectively.It showed that UMAP was an attractive method for extracting LSPs with fast speed and high efficiency.(2)The technology of removed protein of lotus seeds polysaccharides was studied by combination of Papain and Sevag.The best technological conditions of removed protein were obtained as following:enzyme temperature 50?,enzymatic hydrolysis time 50min and the content of enzyme 120 U/mL.Under this conditions,the rate of removed protein could reach to 74.25%,the rate of losing polysaccharides was 5.88%.Then treated polysaccharides with Sevag twice,the rate of removed protein could reach to 85.5%,however,the rate of losing polysaccharides was 7.5%.Lotus seeds polysaccharides were isolated and purified by DEAE-52 cellulose column and Sephadex G-20.The purity of polysaccharide fraction was identified by Uv-vis spectrum scanning method.The results showed that lotus seeds polysaccharides were a single fraction.The polysaccharide component has no characteristic absorption peaks of protein and amino acids near 260nm and 280nm,indicating that the component is a polysaccharide with higher purity.(3)The molecular weight of purified lotus seed polysaccharides was determined by SEC-MALLS-RI system.The molecular weight distribution of lotus seed polysaccharide was 1.0×104-7.0×104 g/mol,the weight average molecular weight Mw was 2.360×104(±0.453%)g/mol and the average molecular weight was 2.089×104(±0.438%)g/mol.The infrared spectrum results showed that the polysaccharide was mainly a-type glycosidic bond.The microstructure of lotus polysaccharide was observed by field emission scanning electron microscope.The results showed that lotus seed polysaccharide was honeycomb.The effect of purified lotus seed polysaccharide on Lactobacillus bulgaricus was studied in vitro.The results indicated that lotus polysaccharide had a good effect on the growth of Lactobacillus bulgaricus,and its effect was better than that of inulin and glucose,which proved that lotus polysaccharide was a potential prebiotics.