Screening Of Lactic Acid Bacteria Producing Folic Acid And Its Application In Fermented Milk

Vitamin is an essential nutrient for human body.It has been proved that lactic acid bacteria can produce vitamin and indirectly supplement the vitamins needed by human body.The application of vitamin producing strain in the research and development of fermented milk is of great significance to the industrial application of lactic acid bacteria and the development of new fermented milk products.This article through to produce vitamin folic acid producing strains screening experiment,in particular,won two strains folic acid yield higher bifidobacterium,applies the mixed fermentation fermented milk,folic acid content in the process of fermentation and storage were determined,and to add folic acid producing strains in the process of milk fermentation and storage of volatile flavor substances were determined.The main results are as follows:Bifidobacterium Breve B2798 and Bifidobacterium Longum subsp.infantis B1398 were screened out by the determination of vitamin content in the fermentation superculture of the strain.Folic acid content in the fermentation supernatant was 7.34 μg/100 g and 5.84μg/100 g,respectively.The physiological,biochemical and fermentation characteristics of the two Bifidobacterium strains were studied.The optimum growth temperature of B.breve B2798 was 37℃ with weak hydrophobicity,and the self-aggregation was 77.67% at 24 h.The supernatant and cell suspension of B.breve B2798 showed good antioxidant capacity,and the supernatant had obvious inhibitory ability against Staphylococcus aureus,Escherichia coli and Bacillus cereus.B.longum subsp.infantis B1398 showed low hydrophobicity at 37℃ and 75.78% self-aggregation at 24 h.The fermentation supernitant and cell suspension of B.longum subsp.infantis B1398 showed good antioxidant activity.All of them had scavenging ability on DPPH,superoxide anion and hydroxyl radical,and their fermentation supernatant had obvious inhibitory ability on Staphylococcus aureus,Escherichia coli and Bacillus cereus.B.breve B2798 and B.longum subsp.infantis B1398 were mixed with a base starter(including Streptococcus thermophilus and Lactobacillus bulgaricus)and applied to milk.It was found that the folic acid content of B1398 group was 6.07 μg/100 g at the end of fermentation and 6.62 μg/100 g at the end of storage,which was significantly higher than that of the control group(P < 0.05).The water retention and viscosity of fermented milk in group B1398 were stable.177 volatile flavor compounds were detected during fermentation and storage.Some important flavor compounds,such as acetic acid,caproic acid and caprylic acid,endowed the fermented milk with good flavor and taste.In conclusion,B.breve B2798 and B.longum subsp.infantis B1398 have high folic acid production,and their application in fermented milk increases the folic acid content of fermented milk,indicating that folic acid producing strain has a good application prospect in the development and utilization of fermented milk.