Study On The Correlation Between Lactobacillus Acidophilus And Astragalus Membranaceus

Astragalus is a traditional Chinese herbal medicine, the effective components of Astragalus are Astragalus polysaccharides and Astragalus flavonoids, which have the functions such as antiviral, anti-inflammatory, anti-aging, antitumor, antioxidant and hepatoprotective activity, treatment of diabetes and reducing cerebral ischemic injury and other pharmacological actions. Lactobacillus acidophilus is common probiotics that can be used to adjust the balance of the intestinal bacteria group of the body and it is very beneficial for human health. In this paper, fermentation characteristics change and enzyme production capacity of Lactobacillus acidophilus after adding Astragalus were studied, and growth medium with additional Astragalus for Lactobacillus acidophilus was optimized and the crude polysaccharides change in the Astragalus fermentation liquid were studied after fermented by Lactobacillus acidophilus and the crude polysaccharides fermentation conditions were further optimized. Astragalus membranaceus and Lactobacillus acidophilus were preliminary studied. Astragalus extracts prepared by water decoction were identified by infrared spectrometer. The results showed that the extracts contain polysaccharides. An ultrasonic method was used to extract the total flavonoids of Astragalus membranaceus. The optimum ultransonic extraction conditions were as follows:temperature of65℃,ethanol concentration of65%,solid-liquid ratio of1:15(g/mL), ultrasonic time of30min and the extraction rate of total flavonoids of Astragalus was0.418%.The morphology, physiology and biochemistry, growth cycle and pH of Lactobacillus acidophilus were studied for culture optimization, of this strain. The orthogonal experiment design was used to optimize the enrichment medium for Lactobacillus acidophilus by using Astragalus as a factor. The results showed that the optimal combination of medium were as follows:glucose25g/L, K2HPO42g/L, yeast extract25g/L, diammonium hydrogen citrate2g/L, sodium acetate2g/L, MgSO4·7H2O0.58g/L, MnSO4·4H2O0.25g/L, astragalus powder lg/L, fresh carrot juice100ml/L.Adjust Astragalus extracts prepared to a concentration of0.008,0.016,0.032,0.064and0.128g/mL, respectively and add to the modified MRS medium to study effect of different concentrations of Astragalus extracts on the growth and enzyme production ability of Lactobacillus acidophilus.The results showed that a concentration of0.032mg/mL in the modified MRS medium could obviously promote Lactobacillus acidophilus proliferation,and the pH was3.88under this condition.Futhermore, under a concentration of0.016mg/mL, the activity of β-galactosidase, glucose oxidase and a-amylase produced by Lactobacillus acidophilus reached the maximum value,which were387.56,14.42and4.4U,respectively.The crude polysaccharide produced in the fermentation broth was optimized by response surface methodology. Through the analysis of Design-Expert software, the optimal fermentation conditions were abtained as follows:sucrose2.28g, yeast powder2.5g, temperature38℃, pH5.5, inoculum3%, liquid volume60/250mL, fermentation time33.71h, Astragalus powder1g. Under these conditions, the yield of crude polysaccharide was12.08%, which was18.3%higher than before.Astragalus flavonoids extract which prepared under the optimal condition were added to the modified MRS culture medium and the effects of Astragalus flavonoids on growth and pH of Lactobacillus acidophilus were analyzed, when the volume of added Astragalus flavonoids was8mL,0.9984mg of Astragalus flavonoids was abtained and the top biomass production of Lactobacillus acidophilus was gained, at pH3.02. Rutain of Astragalus flavonoids extract was identified by thin layer chromatography. Rutin and quercetin content of Astragalus flavonoids extract and fermented Astragalus flavonoids was measured by high-performance liquid chromatography, the results showed that the Astragalus flavonoids extract containing3.4662μg/mL of rutin, but with no quercetin and not rutin or quercetin was found in fermentation broth. After fermenting by Lactobacillus acidophilus for rutin, the content of rutin in fermentation liquid was reduced by97.43%, the content of quercetin increased0.043%, which that Astragalus flavonoids extract could promote the growth of Lactobacillus acidophilus and a small amount of rutin in the extract appeared, partial conversion.