Optimization Of A High-density Fermentation And Drying Process For A Strain Of Saccharomyces Boulardii

Due to the increase in drug-resistant strains caused by the abuse of antibiotics in feed and the increase in the resistance of pathogenic microorganisms,new green feed additives are urgently needed to be developed and applied.Yeast is one of the most widely used microbial feed additives.Among them,Saccharomyces boulardii not only possesses the nutritional properties of ordinary yeast,but also effectively balances the intestinal microstable state and improves immunity.The Saccharomyces boulardii must pass through the acid environment of the stomach and enter the intestinal tract in order to exert its probiotic effect,so the preparation process of the fungus is particularly important.In this paper,molasses is used as the main raw material for high-density fermentation of Saccharomyces boulardii.After spray drying,cold blast drying and microencapsulation technology,the yeast is post-treated to obtain a Saccharomyces boulardii preparation that is resistant to gastric acid environment.1. The optimal growth temperature for Saccharomyces boulardii is 28?,the optimal p H is 4.5,and the optimal carbon source is maltose.Using molasses as the main carbon source,a 50L fermentor is used for batch feed fermentation.The fermentation time is 43h.The wet weight of Saccharomyces boulardii can reach 189.45 g/L,the dry weight can reach 68.94g/L,and the number of viable bacteria is 39.24×10⁸ cfu/m L.The total sugar conversion rate is 45.06%,which is close to the theoretical conversion rate of 50%.2. Set the inlet air temperature to 120°C,the outlet air temperature to 55°C,and the feed pump speed to 1000 r/h to optimize the spray drying process for Saccharomyces boulardii.Through single factor screening and orthogonal experiments,it was determined that the dry protectant formulation was skimmed milk powder 14%,sucrose 2.5%,sodium L-glutamate 0.5%,mannitol 3%,and the fungus drying survival rate could reach78.69%..3. The extrusion method was used to study the microencapsulation technology of Saccharomyces boulardii.The response surface method is used to optimize the preparation process:the best preparation formula is sodium alginate concentration?w/w?2.48%,whey protein?WPI?concentration?w/w?6.06%,and solidification solution?Ca Cl₂?concentration 0.01 mol/L,curing time 10min.It was prepared by extruding with a7-gauge needle?inner diameter 0.41cm?.After drying at 28°C for 3 hours,the survival rate can reach 87.37%,the survival rate of gastric juice can reach 95.60%,and the number of viable microcapsules is 12.5×10⁸ cfu/g..4. The microcapsule cold blast drying process is optimized.Set a drying temperature of 28°C and a humidity of 10%.Screen the commonly used protective agents for Saccharomyces boulardii.Use orthogonal experiments to determine the cold blast drying protective agent is 1%L-glutamic acid sodium,7.5%trehalose and 5%maltose.The survival rate of drying in orthogonal test is up to 97.85%.