Flavonoids Content,Composition And Antioxidant And Antibacterial Activities Of Probiotics Fermented By Probiotics Impact Study

Dandelion is a kind of clearing and detoxifying traditional Chinese medicine for medicine and food.It contains a variety of active substances,and flavonoids are one of its main components.In this experiment,the dandelion was fermented by probiotics,and the effects of different fermentation strains,synergists and fermentation conditions on the flavonoid content of dandelion were analyzed.The effect of fermentation on the constituents of dandelion flavonoids was analyzed based on UPLC-MS method.Its anti-oxidative activity and antibacterial activity in vitro.The paper mainly includes the following three parts:1 Effect of probiotic fermentation on flavonoids content of dandelion1.1 Effect of Fermentation Strains on the Content of Flavonoids in DandelionUsing flavonoids as indicators,the bacterium was fermented with single bacteria by using four strains of Lactobacillus plantarum,Saccharomyces cerevisiae,Bacillus subtilis and Bacillus licheniformis,and the two strains with the best fermentation effect(Lactobacillus plantarum and Saccharomyces cerevisiae)were used.Fermentation and further screening of the proportion of strains.The results showed that the fermentation efficiency of S.cerevisiae and Lactobacillus plantarum was the best in 7:3 ratio,and the flavonoid content of dandelion was 57.79 mg/g.1.2 Effect of synergist on flavonoids content of dandelionThe effects of 10 synergists such as urea,casein,sucrose and molasses on the content of dandelion in the fermentation products were compared.The results showed that the effect of yeast extract on flavonoids content of dandelion was significant(P<0.05).The optimum amount of yeast extract was 0.5%.At this time,the flavonoid content in dandelion reached 61.50 mg/g.1.3 Effects of fermentation conditions on flavonoids content of dandelionThe flavonoid content of dandelion was used as the index,and the fennentation conditions(fermentation time,fermentation temperature,inoculum amount,water content)of probiotic fermentation dandelion were optimized by single factor combined response surface design method.The optimal fermentation conditions were:fermentation temperature 35.34?,fermentation time 52.04 h,inoculum 12%,water content 52.69%.Under the fermentation conditions,the flavonoid content of dandelion reached 66.95 mg/g,which was 8%higher than before optimization.1.4 Preparation of crude flavonoids from dandelionFermented dandelion was prepared based on the above fermentation conditions,and the dandelion was treated with water extraction and alcohol extraction before and after fermentation,and the content of fermented dandelion flavone(FDF)and unfermented dandelion(DF)was 183.72 mg/g and 109.49 mg/g,respectively.FDF increased by 67.80%compared with DF.2 Effect of probiotic fermentation on the constituents of dandelionUltra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS)was used to analyze FDF and DF.229 kinds of dandelion flavonoids were identified,including 131 kinds of flavonoids,35 kinds of flavonols and 26 kinds of tlavanones.Principal component analysis showed that there were large differences in the composition of FDF and DF.Further screening for differential metabolites of fermented and unfermented flavonoids,a total of 57 differential metabolites were screened,and 27 metabolites were up-regulated(eg:uercetin 3-O-rutinoside,daidzein,etc.),30 metabolites are down-regulated(such as safflower biflavonoid,naringenin-7-O-glucoside,etc.).Twenty-five of the 57 differential metabolites have been annotated,indicating that flavonoid metabolites in dandelion are more abundant after microbial fermentation.FDF and DF are completely different types of flavonoid metabolites,and the bioactive components in FDF are effectively increased.3 Biological activity of fermented dandelion flavonoids3.1 Antioxidant activity researchIin this study,the effects of fermented dandelion flavone(FDF)and dandelion flavone(DF)on DPPH free radicals and reducing power were compared to evaluate the in vitro oxidation activity of fermented dandelion flavonoids.The results showed that the reducing power and DPPH free radical scavenging rate of FDF were significantly higher than DF(P<0.05).3.2 Antibacterial activity researchThis experiment compared the antibacterial activity of fermented dandelion flavone(FDF)and dandelion flavone(DF)against Staphylococcus aureus and Salmonella.The study found that the IC50 values of FDF against Staphylococcus aureus and Salmonella were 18.50 mg/mL and 12.35 mg/mL,respectively.The IC50 values of DF against Staphylococcus aureus and Salmonella were 20.73 mg/mL and>25 mg/mL,respectively,indicating that the fermented dandelion flavonoids had significant antibacterial activity compared with unfermented dandelion.Fermented dandelion flavonoids contain more abundant flavonoid metabolites,and their antioxidant and bacteriostatic activities are significantly higher than unfermented dandelion,which can be used as a functional feed additive in livestock production and breeding.