Study On Method To Improve The Heat Resistance Of Lactobacillus Plantarum LIP-1 During Spray-drying

The survival rate of strain drastically reduces in a atmosphere of high temperature during the preparing process of probiotics powder using spray-drying.From a point of a view that is to improve the heat resistance of lactobacillus plantarum LIP-1,the effect and internal mechanism on the strain were researched by means of optimizing the culture media,changing the original pH value of culture media,heat shock and the following repairing culture of the strain.On the basis,the strain was used as the core material,and the skim-milk complex solution as the wall material,and the aqueous phase separation method was for preparing the probiotics microencapsulation.Furthermore the microcapsules' survival rate and storage stability after spray-drying were evaluated.A continuous process was established by combining the above measurements for improving the spray-drying survival rate of lactobacillus plantarum LIP-1.Result has shown that the thermal-killed survival rate of the strain increased from 10.00%to 41.50%based on ensuring the normal growth of strains when added 1%(w/w)sucrose,1%(w/w)lactose,0.02 mol/L Mg2+,4 mmol/L Mn2+ and 3.6 mmol/L adenine into MRS medium.When original pH value of the medium was adjusted to 6.4,the PH value of environment decreased significantly caused by growth of the stain.The increase of content of some long chain unsaturated fatty acids in cell membrane reinforced the stability of the cell membrane.Therefore the thermal-killed survival rate of the strain rose to 51.50%,at the same time the slight acidic environment(pH 6.4)made a significant enhancement of amount of viable count(p<0.05),After that the strain was been heat shocking in 44? water bath for 10 min,the strain's expression of heat shock protein-related genes GroES,GroEL,DnaJ and GrpE were up-regulated,and the thermal-killed survival rate of the strain was improved to 71.00%.Repairing culture was rapidly operated at 30?,10 min after the heat shock,then the thermal-killed survival rate of the strain was improved to 85.60%.results of NaCl sensitivity test and LIVE/DEAD cell staining test had indicated that the cell membrane suffered from injury was significantly repaired in this step(p<0.05).When the heat treated stain was microencapsulated using the aqueous phase separation method,the spray-drying survival rate and the storage stability was significantly higher than the untreated or not microencapsulated stain.The heat resistance of lactobacillus plantarum LIP-1 was significantly improved via the heat-shock and repairing culture and the microencapsulation method.This study provides a theoretical reference for overcoming the heat damage of probiotics and has practical significance for the industrial promotion of probiotics powder prepared by spray-drying.