Study On The Development Of Fermentation Agent For Lactic Acid Bacteria With High Adsorption Of Lead

The problem of heavy metal pollution has seriously threatened people's health,and it was found that lactic acid bacteria have certain absorption capacity for heavy metals.With the improvement of food safety and health care requirements,lactic acid bacteria with heavy metal adsorption capacity show great application prospects.Based on four strains of lactic acid bacteria with adsorption capacity for heavy metal lead in the previous period of this experiment,they were combined with lactic acid bactiria isolated from Tibetan yak dairy products,which had good fermentation characteristics.According to the adsorption capacity and fermentation ability of the combined strains,the optimal combination was selected for single factor fermentation condition test and response surface optimization test.Finally,the optimal fermentation conditions of the dominant strains with heavy metal lead adsorption were obtained.The absorption capacity of 4 strains of Streptococcus pentose Fe3,Ff3,9b1,10a1 Pb2 was 8.92 mg/L-8.96 mg/L and the adsorption rate was 94.55%?98.70%.The growth ability,fermentation performance and aroma production ability of 40 strains of lactic acid bacteria isolated from Tibetan yak dairy products were determined.Finally,4 strains of cocci were selected,TG7-1-6,TG7-1-1,TG8-1-5,RM1-1-20,and 4 strains of bacilli,RQ1-1-1,RQ1-1-16,TG8-1-9 and TG5-1-6,respectively.Two combinations of 4 strains of cocci and 4 strains of bacilli were selected,and then combined with 4 strains of Pediococcus pentosaceus Fe3?Ff3?9b 1?10al with adsorption Pb2+ability to produce a total 64 strains.The adsorption capacity and adsorption Tate of 64 strains on curd time and titration acidity of fermented milk of 64 strains were determined,and finally the RM1-1-20,TG8-1-9,10a1,the gelation time was 9.5h,the titration acidity was 83,83°T,and the Pb2+adsorption capacity and adsoxption rate were 8.77mg/L,79.73%,respectively.Single factor test of fermentation conditions was carried out with the selected optimal strain combination.The single factor was fermentation temperature(30?,34?,37?,40?,42),the total inoculation amount(3%,4%,5%,6%,7%),and the inoculation ratio between strains(cocci:bacilli:adsorption characteristic strains were 2:1:1,1:1,1:1:1:1:2,1:1:3,1:1:4).The results showed that 37? was the optimum fermentation temperature,6%was the optimum inoculation amount,and 2:1:1 was the optimum inoculation ratio.On the basis of single-factor test,The titration acidity and curd time were taken as the reponse values,and the fermentation temperature,total inoculation amount and inoculation ratio were selected as the test factor base for the fermentation surface response serface optimization test.The results showed that the fermentation temperature was 37.73?,the total inoculation amount was 5.31%,the inoculation ratio was 2:1:1,the theoretical titration acidity was 85.24°T,and the gelation time was 3.28 h.The best process conditions were revised as follows:fermentation temperature 37.7?,inoculation ratio 5.2%,inoculation ratio 2:1:1.The verification experiment was carried out under this process condition.The titration acidity was 87.58°T,and the error of the predicted value was 2.34;the condensed milk time was 3.5 h,and the error of the predicted value was 0.22 h,which indicated that the model could simulate and predict the optimum fermentation conditions of starter.This provides experimental data and strain resources for the production of lactic acid bacteria starter with adsorption characteristics.