| Korean traditional fermented food is a major feature of Yanbian area.Its food culture is rich and interesting.Representative fermented foods including various kinds of kimchi,pickles,sauces,etc.are the most basic and most popular flavors of local people,with a long history of eating.The lactic acid bacteria in fermented food can improve food safety,improve sensory characteristics,enrich nutrients,and benefit human health.In this test,106 strains of suspected lactic acid bacteria from the calcium-soluble circle were isolated from 11 traditional Korean pickles originating from Yanbian area.The strains that could survive in the environment of pH 1.5 were screened by the acid resistance preliminary screening test.Species were identified by morphology,physiology and biochemistry and 16SrDNA gene fragment sequence analysis.The strains with the best potential probiotic characteristics were selected through a series of in vitro probiotic characteristics tests such as tolerance of artificial gastric juice,tolerance of artificial intestinal fluid,bile salt tolerance,hydrophobicity,self-agglutination ability,and cholesterol degradation ability.The main findings are as follows:(1)Initially screen the 106 strains isolated and screened for acid resistance,and finally screen 5 strains with better tolerance in the environment of pH 1.5,which are D4,D5,D9,D19,D30.(2)5 strains were observed to be purple by Gram staining,and belong to Gram-positive bacteria,short rod-shaped;The catalase test showed that the strains did not produce gas,and these 5 strains could be judged the catalase test of the strain was negative;The sequence analysis of 16S rDNA gene fragments identified D4?D9?and D30 as Lactobacillus paraplantarum,D5 as Lactobacillus paracasei,and D19 as Lactobacillus plantarum.(3)In the artificial gastric juice tolerance test,after digesting the artificial gastric juice for 3 hours at pH 2.5,2.0,and 1.5 respectively,the survival rate of D4 are 30.73%,0%,and 0%respectively;The survival rates of D5 are 120.15%,49.88%,and 0%respectively;The survival rates of D9 are 28.38%,1.17%,and 0%respectively;The survival rates of D19 are 70.19%,1.23%,and 0%respectively;The survival rates of D30 are 25.47%,3.17%,and 0%respectively.It can be seen that D5 has the best tolerance and D30has a poor tolerance.(4)In the artificial intestinal fluid tolerance test,after the strains were digested with gastric juice of different pH values and then digested with artificial intestinal fluid with pH value of 6.8 for 8 hours,the survival rates of D4 were 28.37%,0%,and 0%respectively;D5 survival rates are 64.12%,32.67%,and 0%respectively;D9 survival rates are 36.13%,0%,and 0%respectively;D19 survival rates are 53.54%,0%,and 0%respectively;D30 survival rates are 21.68%,0%,and 0%respectively.It can be seen that D5 has the best tolerance to artificial intestinal fluid,and D30 has a poor tolerance.(5)In the bile salt tolerance test,the survival rates of D4,D5,D9,D19,and D30 were 15.20%,22.35%,15.19%,10.64%,and 15.65%after culturing under 0.3%bile salt conditions for 8 hours.It can be seen that D5 has the highest survival rate,followed by D9,D30,and D4,and strain D19 has the lowest survival rate.(6)In the hydrophobicity test,the hydrophobicity ratios of D4,D5,D9,D19,and D30 were 55.67%,67.00%,64.28%,72.17%,and 60.17%,respectively.Among them,the most hydrophobic is D19,and the lowest is D4.(7)In the self-agglutination ability test,after the strain was cultured in PBS buffer solution for 24 hours,the highest self-agglutination rate was 67.17%for D19;followed by 60.33%for D9,56.33%for D4,52.67%for D5,and D30.The self-agglutination rate is relatively low at 50.83%.(8)In the cholesterol degradation test,D5 has a stronger degradation ability,and the degradation rate is 70.13%.The degradation rates of D4,D9,D19,and D30 are 63.08%,65.18%,63.20%,and 63.04%,respectively. |
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