Screening Probiotic With Gastrointestinal Tract Stress Resistance And Its Product Exploitation

Lactobacillus acidophilus and Bifidobacteria are important probiotic in gastrointestinal tract of human, their viable counts in gastrointestinal tract can estimate healthy degree of organisms, which would benefit the human health and could be used in probiotic industry:resistance to acid and bile; attachment to the human epithelial cells; colonization in the human intestine; production of antimicrobial substances, called bacteriocins; increase of the lactose tolerance and digestion; cholesterol reduction; reduction of ammonia and other toxic compounds; production of the B vitamins; restoration of the normal intestinal microflora after antibiotic therapy; stimulation of the immune response. The application of probiotic products face currently with the various problems such as damage during manufactures storage and sales in China. Bifidobacteria, Lactobacillus acidophilus and other probiotics are anaerobic bacteria or facultative anaerobe, and little resisting to bad environments because they don’t form spores during growth, moreover are inhibited by lactic acid, acetic acid and other substances from themselves metabolism in the liquid environment, so that viable cells counts of probiotic decreased sharply during long storage. Most liquid/frozen probiotic cultures require refrigeration for storage and distribution, thereby adding expense and inconvenience to their widespread use such as short shelf. However these cold-chain requirements may be greatly reduced or eliminated through the use of dry powders, which potentially superior to liquid/frozen state in their sterility and stability, and accomplish supplement of probiotic any time.This subject firstly focused on screening the probiotic strains with fine gastrointestinal tract stress resistance and ideal characteristics, L. acidophilus AD1and AD2, B. animalis subsp lactis2.0001,2.0002and2.0604were isolated, identified by16S rDNA gene sequence analysis. Then researching their probiotic properties and optimization of cryoprotectants skim milk, sucrose, trehalose and Vc sodium salt, and assessing the stability of freeze-dried probiotic powder during storage. Regards5yogurts fermented respectively by2L. acidophilus and3B. animalis as the research subject, surveys their pH value, titratable acidity, dynamic rheology and texture profile, study fermentation of semi-works on five probiotic with3.6L fermenter, respectively, and determination main metabolites with HPLC, designing finally successfully probiotic powder pipette.Results of probiotic properties demonstrated that five strains had strong tolerance to simulated gastric juice and bile salts, and B. animalis strains displayed acid tolerance better than L. acidophilus strains. Antimicrobial susceptibility and drug resistance data suggested that five probiotic inhibited E. coli, Staphylococcus and Salmonella, All of5probiotics could be sensitive to acetylspiramycin, streptomycin and penicillin. The optimal combination gained from single factors and direct cross experiments demonstrates that the freeze-dried survival rates of five strains were all above85.00%. The stability dates suggested that the viable cell counts of5probiotic powder were all above1.0×108cfu/g under4℃and25℃for12months, and reached high levels of viable microorganisms recommended by FAO/WHO in excess of106～107cfu/ml in probiotic foods for efficacy. The stability of probiotic powder under4℃was better than25℃. Fermentation results showed that texture and viscoelasticity of L. acidophilus KLDS AD2fermented milk were the best in all samples. The HPLC suggested that L. acidophilus liked to produce lactic acid, and B. aimalis preferred to produce acetic acid. The design of probiotic powder pipette was successful, which could match with various beverages such as bottling water, fruit juice, milk and other types of beverages.The subject screens the probiotic with gastrointestinal tract stress resistance and researchs its application of dried powder form, resolves problems that probiotic was sensitive to liquid environment, overcomes high viable cells1.0×108cfu/g required by FAO/WHO after12months storage, which can produce healthy effects for human.