Optimization Of Two Probiotic Lactic Acid Bacteria And Their Evaluation Of Intestinal Function

Lactic acid bacteria are one of the main flora in the human and animal intestine,which can regulate the balance of intestinal flora and play an important role in maintaining the intestinal health of organisms.Different lactic acid bacteria have different probiotic characteristics.In this paper,based on the enterprises with two strains of lactic acid bacteria RG1(Lactobacillus casei),RG2(L.rhamnosus)as object,study its growth,gastrointestinal tolerance and cultivation characteristics,and evaluate its regulating intestinal flora and purge function.The main results and conclusions are as follows:1.Growth and Gastrointestinal Tolerance Characteristics of RG1 and RG2The activated RG1 and RG2 strains were inoculated in MRS liquid medium and sampled every 2 h to determine the pH and OD values of the bacterial suspensions.The growth trend of RG1 and RG2 was similar,the delay period was 2 h,2~12 h entered the logarithmic phase,during this period,the number of bacteria increased exponentially,entering equilibrium at 12~20 h,and entering recession at 20 h.By simulating the environment of the artificial gastrointestinal tract,the viability of viable bacteria was measured using RG1,RG2 at pH 4.0,bile salt 0.3%,artificial gastric juice,and artificial intestinal fluid for 3 h.Both RG2 and RG2are highly tolerant to artificial gastrointestinal fluids.The survival rate of RG1 in artificial gastric juice is 55.20%for 3 h and 68.45%in artificial intestinal fluid.The survival rate of RG2 in artificial gastric juice for 3 h is 77.50%,the survival rate of artificial intestinal fluid is87.75%.2.Optimization of culture conditionsThe effects of carbon source,nitrogen source,antimicrobial substance,culture temperature,initial pH value on the growth of lactic acid bacteria were studied based on MRS medium and OD value of suspension.The optimum conditions of RG1 culture were as follows:adding glucose 1,peptone 2,fresh carrot juice 10,pH 6.1,culture temperature 34℃for 18 h,adding glucose 2 and peptone 1,fresh carrot juice 10 and pH 5.9,at 37℃for 18 h.3.Effect of RG1 and RG2 on the function of mice’s laxative functionTo establish a model of constipation in mice by orally administrating compound diphenoxylate tablets by oral gavage,and irrigating 1.0×10~8CFU/mL of RG1 and RG2bacterial suspensions,respectively.From the small intestine ink advancement rate,defecation time,the number of black stools within 5 h,and the weight of black stools,the defecation function of the RG1 and RG2 experimental groups was superior to that of the model control group(P<0.05),and RG1 was superior to RG2(P<0.05).4.Effect of RG1 and RG2 on intestinal microflora in miceInoculate RG1 and RG2 bacterial suspensions with an aqueous suspension of 1.0×10~8CFU/mL,respectively,afterwards we compare the changes of bifidobacterium,lactobacillus,enterobacter,Clostridium perfringens.The results showed that RG1 and RG2 could promote the increase of bifidobacterium and lactic acid bacteria significantly(P<0.05).The effect of RG2 was better than that of RG1 and mixture of RG1/RG2.There was no synergistic effect between RG1 and RG2 and RG1 in regulating the balance of intestinal flora in mice.