High-density Fermentation Of Lactobacillus Plantarum ZJ316 And Preliminary Study On The High Activity Bacteria Agent

The term“Probiotics”originally refers to a body of living microorganisms that have significant influences on other cellular organisms and ensure wellbeing through improving microbial flora.Now it refers to a class of active microorganisms that are beneficial to the host by colonizing the host's intestinal tract to improve the composition of the host flora.Lactic acid bacteria can inhibit the growth of pathogenic bacteria,inhibit the formation of tumor cells and other physiological functions,so it has the potential to be applied to the feed industry.In order to make full use of the functions of probiotics and develop the market of its products,the protection and improvement of the viable count has become an urgent problem to be researched and solved.The present research took,Lactobacillus plantarum ZJ316,as test object.On the basis of MRS medium,through single factor test and response surface combination design(Box-Behnken design,BBD)test,the optimal fermentation medium was as follows:sucrose 43.405 g/L,corn steep liquor 59.464 g/L,Na₂HPO₄/Citric acid 0.124 mol/L,MgSO₄·7H₂O 0.2 g/L,MnSO₄·H₂O 0.1 g/L,Tween 80 1 ml/L.By single factor experiment,optimized the fermentation conditions for L.plantarum ZJ316:initial pH 6.5,cultivation temperature is 30?,inoculation amount 4%,shaking speed 50 r/min.We scaled up the culture process in a 5 L fermenter under the optimal conditions,and the growth cure of L.plantarum ZJ316 was gotten.After 24 hours of fermentation,the viable count could reach 8.01×10⁹ CFU/mL.The freeze-dried protective agent and storage conditions of L.plantarum ZJ316 were optimized by single factor and orthogonal experiments.The optimal cryoprotectants for the strain was obtained as follows:trehalose 12%,maltodextrin 10%,sucrose 12%,non-fat powdered milk 3%,the survival rate of the bacterial agent after freeze-drying was 88.5%under this condition.The tolerance of freeze-dried bacterial preparations was evaluated,and it was found that the strains still had strong tolerance in bile salts,Na Cl,low pH and artificial simulated gastrointestinal juice after the vacuum freeze-drying.The microbial agent obtained by vacuum freeze-drying has the best effect when it was stored at 4°C?-20?.The suitable carrier for preparing microbial agent of strain L.plantarum ZJ316 was screened.Three carriers of rice bran,bran and malt were used to prepare solid microbial agent after high-density cultivation.The results showed that the suitable carrier was rice bran for solid microbial agent of strain L.plantarum ZJ316.After preservation for 30days at 25?,the viable count was 3.67×10⁷CFU/g,and the survival rate was 0.15%.Comparing the effects of houttuynia cordata,siraitia grosvenorii,astragalus,non-fat powdered milk,artemisia annua and trehalose as carriers of liquid microbial agents,the results show that the suitable carrier was trehalose for liquid microbial agents.After preservation for 30 days at 25?,the viable count was reached 6.8×10²CFU/mL.