Study On Freeze-drying Protectant Formula With Lactic Acid Bacteria In Forage

Lactic acid bacteria are one kind of additives of silage which is able to addedin the fresh grass and produce lactic acid rapidly. The lactic acid can forbid thegrowth and propagation of malignant bacteria, and the quality of silage is alsoincreased. With the rapidly development of animal husbandry, it will be veryimportant to study high activity and harmless concentrated silage additives forpromoting the industrial process of animal husbandry.In this paper, we used stain Lactobacillus plantarum and Leuconostocdextran subspecies as objects,to study their growth conditions, method ofenhancement and enrichment bacteria, freeze-drying protection and rehydration.1. The growth condition of L.P and L.D were compared and studied. Theresults showed that the L.P was inoculation at14h and the L.D was inoculation at16h, they will get to the end of the logarithmic phase. The optimum growthtemperature of L.P is35℃and L.D is25℃. The inoculation can effects the end ofthe logarithmic phase, but it can not to change the biomass of two bacterial strain.2. The organic nitrogen source are more effective to promote the growth oftwo bacterial strain than inorganic nitrogen. The viable count of L.P and L.Dachieved maximum when peptone concentration is3%, the L.P is5.06×10~9cfu/mLand the L.D is3.17×10~9cfu/mL. The viable count of L.P and L.D achievedmaximum when glucose concentration is6%, the L.P is1.21×10~10cfu/mL and theL.D is7.36×10~9cfu/mL. The optimum growth pH of L.P is between5.0～6.2andL.D is between5.4～6.2.3. The effects of centrifugation condition on livability of Lactobacillusplantarum and Leuconostoc dextran subspecies were studied in this research. Theresult manifested that the most optimum condition parameter for preparing the twoboth of them suspension were10min,5000r/min. The L.P and L.D had the highestsurvival rate when the bacteria suspension was freeze-dried at-20℃in advance. The optimum cryoprotectants formula for Lactobacillus plantarum was determinedby the orthogonal trial as: nonfat milk powder15%, trehalose3%, glycerol6%,ascorbic acid2%; the optimum cryoprotectants formula for Leuconostoc dextranwas determined as: nonfat milk powder15%, treha lose6%, glycerol1%, ascorbicacid2%.Then the surviving rate of L.P and L.D can reached88.21%and90.02%.The L.P and L.D had the highest survival rate when the rehydrated media is choose12%nonfat milk powder.