| Hyperglycemia can cause diabetes,and is extremely harmful to human health.Lactic acid bacteria has been recognized as beneficial edible bacteria with a variety of functions to human health,and continuing research on its new functionality is on the way.Meanwhile the study on the effect of lactic acid bacteria on hypoglycemia and its health products has gradually become a hot spot.The research objects are 18 strains of lactic acid bacteria as SL01,SL0,SL0,SL06,SL08,SL08,SL09,SL10,SL11,SL12,SL13,SL14,SL15,SL16,SL17,SL18.The experimental strains were isolated from traditional fermented food collected in Shaanxi and Gansu.First,we studied on the tolerance of the strains of gastric juice and intestinal juice as well as acid production capacity.Followed we studied on the 18 strains of lactic acid bacteria's suspension and fermentation supernatant and cell breakage supernatant to hypoglycemic-related properties respectively including ?-glucosidase and ?-amylase inhibition and reduction ability,the scavenging ability of free radical DPPH and superoxide anion(O2-·).Strains with better effect of hypoglycemia were selected and employed as fermentation strains.The preliminary preparation of fermented milk hypoglycemic effect was analyzed and tested.The main findings are as follows:Study on the probiotic characteristics of the strains: we studied the morphological characteristics,growth curve,dissolve calcium circle,pH,acid production as well as tolerance of artificial gastric juice and artificial intestinal juice showed that 16 out of 18 strains were bacillus,2 kinds of were coccus;They could both reached the rapidly growing period after 24 h,18 strains all had acid production capacity and the dissolve calcium circle value ranged from1.35cm~2.60 cm,the amount of acid production was 6.84g/Kg~19.98g/Kg;18strains of gastrointestinal fluid tolerance were different,two strains survival rate were below 20% in gastric juice after 3h,13 strains were between 20% to 60%,three strains were more than 60% named SL03,SL02 and SL07.The survivalrates of the two strains were less than 20% in intestinal juice after 6h,while the survival rates of 13 strains were between 20% to 75%.The strains SL03,SL09 and SL18 reached more than 75%.Study on the strains' hypoglycemic effects of the relevant indicators include:18 strains of lactic acid bacteria's suspension and fermentation supernatant and cell breakage supernatant on the inhibition of ?-glucosidase and ?-amylase and reducing ability and the scavenging ability of free radical DPPH and O2-· were studied respectively.They had a certain effect on hypoglycemia,the suspension had no inhibition activity on ?-amylase,but all strains suspension had inhibition activity on ?-glucosidase,it ranges from 5.71% to 37.48% which is higher than the fermentation supernatant and the cell breakage supernatant.There were 17 strains suspension with reducing ability and the reducing concentration ranged from 9.67?mol/L to 46.13?mol/L.4 strains suspension could scavenged free radical O2-·,and the clearance rate was from 3.50% to 23.09%.All the strains suspension could scavenged free radical DPPH,and the clearance rate was from9.73% to 36.63%.The fermentation supernatant had inhibition activity on?-amylase of 17 strains ranged from 5.14% to 33.85%.All strains fermentation supernatant had inhibition activity on ?-glucosidase,it ranges from 1.55% to24.62%.All strains fermentation supernatant also had reducing ability,reducing concentration ranged from 44.75?mol/L to 105.25?mol/L which is higher than the suspension and the cell breakage supernatant.All strains fermentation supernatant could scavenged free radical O2-· and DPPH,both higher than the suspension and the cell breakage supernatant in general.The O2-· clearance rate was from 2.97% to 34.18%.The DPPH clearance rate was from 18.83% to82.92%.The cell breakage supernatant had no inhibition activity on ?-amylase,but all strains suspension had inhibition activity on ?-glucosidase which ranges from 0.31% to 25.45%.All strains cell breakage supernatant had reducing ability ranged from 1.93?mol/L to 35.64?mol/L.14 strains cell breakage supernatant could scavenged free radical O2-· with the clearance rate was from 0.74% to14.97%.All the strains cell breakage supernatant could scavenged free radical DPPH,and the clearance rate was from 4.45% to 43.54%.Identification of lactic acid bacteria: The results showed that SL01,SL02,SL03,SL05,SL12 and SL18 were better in 18 strains of hypoglycemic effect.The morphological identification and 16 S rRNA gene sequencing demonstrate that SL01 is Lactobacillus sp.,SL02 is Lactobacillus casei,SL18 is Enterococcus faecium,SL03,SL02 and SL12 are both Lactobacillus reuteri.Study on Lactic acid bacteria fermented milk and its indicators related to hypoglycemic effects: The 6 strains of lactic acid bacteria were selected as the fermentation strains for the preparation of fermented milk.The results showed that the fermented milk prepared by the 6 strains had different degrees of hypoglycemic activity,and the effects of different temperatures on the activity of the fermented milk were different.Finally,the condition of fermented milk SL01 ferment at 37? in 72h;fermented milk SL05 ferment at 41?in 72h;fermented milk SL02 and SL18 ferment at 37? in 56h;fermented milk SL12 ferment at41? in 48h;fermented milk SL03 ferment at 37? in 64 h.When the fermented milk of 6 strains were mixed,the hypoglycemic activity was significantly enhanced,hence the results showed that the mixed fermented milk inhibition rate of ?-glucosidase was 25.68%,and the inhibition rate of ?-amylase was 65.27%,the reduction concentration was 152.75?mol/L,the scavenging rate of O2-· was40.82%,and the scavenging rate of free radical DPPH was 65.29%.After refrigerated 21 d,viable bacteria number was 5.3 × 107CFU/mL,the acidity was below 109 oT,and the inhibition rates of ?-glucosidase and ?-amylase were remain at 20.58% and 61.23% respectively.What's more the reduction concentration was 143.38mol/L,the clearance rate of O2-· was 30.97% and the clearance rate of DPPH was 52.62%.After cold storage,the mixed milk still maintained high hypoglycemia activity.In conclusion this paper conducted a research on selection of Lactic acid bacteria with probiotic characteristics as well as hypoglycemic activity and the preparation of fermented milk for lactic acid bacteria.The study provides some theoretical and experimental basis for further research and development of new functional lactic acid bacteria fermented milk. |
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