Degradation Of Nitrite Isolation And Screening Of Lactic Acid Bacteria In Kimchi Fermentation

In this paper,26 strains lactic acid bacteria were isolated from three kinds of pickle,and compared their nitrite degradation ability in MRS liquid medium.Through the initial screening,12 strains which had higher nitrite degradation ability were selected.Then through further screening in MRS phosphate buffer medium,3 strains (c2,h2 and j3) which had higher nitrite degradation ability were choosed from 12 strains.The physiological-biochemical properties of three strains showed that:c2 and h2 were identified to Lactobacillus, j3 was identified to Pediococcus.In order to find out the effect of different conditions on three strains degradation nitrite,temperature,pH,inoculum size,substrate concentration,optimal vaccination age,carbon source and nitrogen source were preliminary study,the results for:①The optimum temperature range of strain h2 which degradated nitrite was 25~35℃,30℃highest;pH range was 6.5~5.5,5.5 highest;Optimal inoculum size was 50‰;When the substrate concentration was 400ug/mL,the degradation activity was highest;Optimal vaccination age range was 6~18h,14h had the highest degradation efficiency.The optimal carbon source was glucose,the optimum nitrogen source was chinese cabbage juice.②The optimum temperature range of strain c2 degradat nitrite was 25~35℃,30℃highest;pH range was 6.0~5.0,5.5 highest;Optimal inoculum size was 50‰;When the substrate concentration was 400ug/mL,the degradation activity was highest;Optimal vaccination age range was 6~14h,10h had the highest degradation efficiency.The optimal carbon source was glucose,the optimum nitrogen source was chinese cabbage juice.③The optimum temperature range of strain j3 degradat nitrite was 25~35℃,30℃highest;pH range was 6.0~5.0,5.5 highest;Optimal inoculum size was 50‰;When the substrate concentration was 400ug/mL,the degradation activity was highest;Optimal vaccination age range was 6~22h,18h had the highest degradation efficiency.The optimal carbon source is glucose,the optimum nitrogen source was soybean peptone.Sereened out the optimal culture media by response surface design experiments,the result for:①The optimal parameters medium of tomato cabbage for strain h2 was:concentration of white juices 41.15%,tomato juice concentration 43.7%,temperature 33.2℃,pH 6.37,OD600 can be up to 1.753.②The optimal parameters medium of tomato cabbage for strain c2 was:concentration of white juices 41.15%,tomato juice concentration 30.22%,temperature 33.2℃,pH 6.59.OD600 can be up to 1.796.③The optimal parameters medium of tomato cabbage for strain j3 was:concentration of white juices 42.12%,tomato juice concentration 47.98%,temperature 34.6℃,pH 5.73. OD600 can be up to 1.898.In application experiments, through single factor experiments and orthogonal design experiment concluded: Mixed fermentation tasted better than single-mode fermentation;The optimum conditions of mixed pickle fermentation were:The proportion of strains was c2: h2: j3 = 1:1:2,temperature 25℃,concentration of salt 4%,inoculum 10%,the initial pH5.5.After 5d,the nitrite content was 1.64ug/mL in pickle fermented juice,peak nitrite(10.12ug/mL) appeared at the next day;In naturally pickle fermented juice,nitrite content was 8.81ug/mL,peak nitrite (36.78ug/mL) appeared at the third day.This showed that vaccination fermentation can effectively reduce nitrite content in pickle,and could shorten the fermentation cycle of pickle.