High Cell Density Culture Of Lactic Acid Bacteria And Its Fermentation And Transformation Of Ginsenosides

Lactic acid bacteria are widely used in industrial fermentation and medical care,and obtaining high-density lactic acid bacteria is of great significance for their commercial production.Ginsenosides have high medicinal value.Lactobacillus plantarum and Lactobacillus reuteri,as lactic acid bacteria,are important strains for transforming ginsenosides.In this study,L.plantarum and L.reuteri were used as research objects to optimize the medium components and culture conditions,and the biotransformation of ginsenoside and ginseng powder by L.plantarum and L.reuteri were further explored,which provided a theoretical and reference basis for the preparation of high-activity and high-concentration lactic acid bacteria starter and the processing of ginseng fermentation products.the result shows:(1)Through single factor experiment,fractional factorial design experiment,the steepest climbing design experiment and response surface design experiment,using L.plantarum ZU018 as the research object and the final viable bacterial count as the main reference index,the fermentation medium components and culture conditions were carried out.The best optimized medium formula was:maltose 30.03 g/L,yeast extract 37.50 g/L,beef extract 25.00g/L,triammonium citrate 4.39 g/L,dipotassium hydrogen phosphate 2.00 g/L,Sodium acetate5.00 g/L,magnesium sulfate 0.20 g/L,manganese sulfate 0.05 g/L,Tween 80 1.00 g/L.The optimal culture conditions are:the culture temperature is 37?,the inoculation amount is 3%,initial pH value is 6.5,and 20%concentration of ammonia is added to maintain the pH of the fermentation broth at 6.5±0.2.The viable count of L.plantarum ZU018 finally reached 2.149×10¹⁰ CFU/m L,which laid the foundation for the subsequent high-density fermentation and application of L.plantarum.(2)The high-density culture of L.reuteri L1 was explored using a similar method.Based on the MRS medium,the carbon source,nitrogen source,total and proportion of carbon and nitrogen,trace elements and growth-promoting factors are screened.The experimental design is used to further optimize the proportion of each main component.Choose the best culture conditions for L.reuteri L1 by monitoring the growth curve of the bacteria.Finally,the best medium components were determined:yeast extract 37.74 g/L,triammonium citrate 2.82 g/L,sodium acetate 8.21 g/L,maltose 60.00 g/L,dipotassium hydrogen phosphate 2.00 g/L,manganese sulfate 0.08 g/L,magnesium sulfate 0.20 g/L,L-cysteine hydrochloride anhydrous0.80 g/L,glycerin 70 mmol/L,Tween 80 1.00 g/L.The optimal culture conditions are:the culture temperature is 37?,inoculation amount is 2%,initial pH value is 6.5,the ammonia concentration is 20%to maintain the pH of the fermentation broth at 6.5±0.2.The viable count of L.reuteri L1 finally reached 1.210×10¹⁰ CFU/m L,which greatly increases the bacterial concentration.(3)Based on the optimization of culture medium and conditions,ginsenosides Rb1,Re,and Rc are selected as substrates,and L.plantarum ZU018 is used for microbial transformation under different fermentation methods,in which the cells collected by centrifugation after high-density cultivation were fermented in the optimized medium mixed with ginsenosides obtained the best results;Under optimal fermentation conditions,the transformation effects of the fermentation time of L.plantarum ZU018,L.reuteri L1 and mixed strains on ginsenosides Rb1,Re and Rc were investigated.The results showed that the transformation effect of L.plantarum ZU018 was the best.Moreover,the conversion rate of rare saponins is higher when fermented for 5 to 6 days.Finally,using high-density cultivation of L.plantarum ZU018 combined with optimized medium,the ginseng powder was fermented and transformed.Compared with before and after fermentation,the content of main ginsenosides was reduced,and new rare saponins F2,C-K and Rh2 were converted.The fermentation broth had antioxidant activity.