Study On The High-density Cultivation And Freeze-drying Processing Of Lactic Acid Bateria

To provide the datas for industrialization of concentrated freeze-dried lactic acid bacteria and establish the technical process and technics parameter of the freeze-dried lactic acid bacteria,the Lactobacillus bulgaricus and Streptococcus thermophillus were choosen as original culture to study their growth condition,method of enhancement,enrichment bacteria and freeze-drying protection.To increase a high amount of the living bacterium,the L.bulgaricus was studied on the culture condition and proliferative substrate.The best culture themperature is 37℃,the best inoculation dosage is 3%,the best initial pH is 6.2,and the best training is plain culture.The best proliferative substrate of L.bulgaricus is:soybean oligosaccharide 2.25%,glucose 2.00%, peptone 1.25%,yeast power 1.25%,tomato juice 6.50%,Tween 80 0.10%,K₂HPO₄ 0.20%. The best culture time is 16h,and the highest amount of the living bacterium is 2.1×10¹¹cfu/ml.To increase a high amount of the living bacterium,the S.thermophillus was studied on the culture condition and proliferative substrate.The best culture themperature is 41℃,the best inoculation dosage is 3%,the best initial pH is 6.4,and the best training is plain culture.The best proliferative substrate of S.thermophillus is:soybean oligosaccharide 2.25%,lactose 1.00%,peptone 1.00%,yeast power 1.25%,tomato juice 6.50%,Tween 80 0.10%,K₂HPO₄ 0.20%.The best culture time is 16h,and the highest amount of the living bacterium is 2.6×10¹¹cfu/ml.Study on the effect of adding alkali and buffer salt on bacteria enhancement.The results shown that,the effect of adding alkali is better than the effect of adding buffer salt.To increase a high amount of the living bacterium,added 20%Na₂CO₃ on culture L.bulgaricusand and added 15%Na₂CO₃ on culture S.thermophillus.Study on the freeze-drying technology of L.bulgaricus.The best centrifugal condition is: revolving speed 4000r/min,time 10min.The best freeze temperature is -20℃,the freeze time is 3h.The best protectant combination is:trehalose10.0%,glycerol 5.0%,Tween 80 0.4%, monosodium glutamate 5.0%.The best preservative pH value is 6.5,preservative and fungi slimy equilibrium time is 30min,and the proportion of mixture of preservative and fungi slimy is 4:1.In the processing of the freeze-drying,the thickness of the fungi slimy is the important elements that affect the result of the freeze-drying,and the water content of the fungi slimy is the important element that affect the reservation time.The best condition confirmed by the experiment is:the thickness of the fungi slimy is 7mm,and the best water content of the fungi power is 2%～3%.Study on the freeze-drying technology of S.thermophillus.The best centrifugal condition is: revolving speed 4000r/min,time 10min.The best freeze temperature is -20℃,the freeze time is 3h.The best protectant combination is:trehalose10.0%,glycerol 7.5%,Tween 80 0.4%, monosodium glutamate 7.5%.The best preservative pH value is 6.5,preservative and fungi slimy equilibrium time is 30min,and the proportion of mixture of preservative and fungi slimy is 4:1.In the processing of the freeze-drying,the thickness of the fungi slimy is the important elements that affect the result of the freeze-drying,and the water content of the fungi slimy is the important element that affect the reservation time.The best condition confirmed by the experiment is:the thickness of the fungi slimy is 7mm,and the best water content of the fungi power is 2%～3%.Put the power of L.bulgaricus and S.thermophillus in the refrigerator at 4℃,sampling at a certain time to get the amount of the living bacterium and calculate the livability.When the reserve time reaches 10 months,determined the amount of the living bacterium is 10⁸cfu/g,can meet the condition that ensure it to have the probiological effect.Therefore,the reservation time is determined at 10 months.