The Study Of Formation Conditions And Tolerance Of Lactobacillus Plantarum SCP53 Biofilm

Lactobacillus plantarum is widely used in fermented food,it is well known and accepted by people because of good features.Biofilm are composed of bacteria and extracellular polymer,and can enhance the adaptability of microorganisms.The biofilm of foodborne pathogenic bacteria tend to increase the difficulty of clear and affect food safety,but we can use the stability of the biofilm structure to apply in probiotics.it may improve the stability and adaptability of the fermentation strains,with a certain commercial value and development prospects.To study the tolerance,gene expression and functional properties of L.plantarum biofilm.This article take L.plantarum SCP53 as test strain which has been filtered and sequencing identified with good fermentation characteristics.By optimizing its culture conditions and nutrients to make a mature biofilm.then test the tolerance of the processing environment,the property of the spray drying powder and the relative expression of genes involved in biofilm formation.The main research conclusions are as follows:(1)Study the formation conditions of L.plantarum SCP53 biofilm by using single factor and orthogonal experiment.The results showed that the temperature,incubation time,pH value affect the formation conditions of L.plantarum biofilm most,and the optimal culture condition for L.plantarum SCP53 biofilm formation were as follows:the inoculum size was 5×107CFU/mL,incubation time was 36 h.culture temperature was at 42 ?,pH value was 5.8.And adding NaCl(40mg/mL),glucose(15mg/mL).pectin(1.5mg/mL),milk powder(15mg/mL)in MRS could promote L.plantarum biofilm formation.A490 values of formatted biofilms were respectively 4.4923 at experimental group and 0.1365 at control groups.By using scanning electron microscopy(SEM)to observe,the biofilm and planktonic bacteria had obvious difference,it had typical biofilm packed with much extracelluar polymeric substances(EPS)and a lot of pores in the biofilm.(2)The tolerance of L.plantarum biofilm on the processing environment had been studied by plate count.The results showed that the mature L.plantarum biofilm have higher tolerance of temperature,pH,salinity,antioxidants,and disinfectants than the unmatured.The temperature tolerance of experimental group is 1.39 times of the control group;PH tolerance is 1.91 times of the control group:NaCl tolerance is 2.46 times of the control group;Nisin resistance is 1.32 times of the control group:Potassium sorbate tolerance is 1.62 times of the control group;Sodium hypochlorite resistance is 1.42 times of the control group;Hydrogen peroxide tolerance is 1.63 times of the control group.Bile salt tolerance is 1.66 times of the control group.(3)The relative expression of L.plantarum SCP53 genes involved in biofilm formation had been determined by real-time quantitative PCR.Results indicate that the relative expression of the related genes BSH,DanK,GroEL.LuxS in biofilm were 0.96?1.53,3.22,2.76.Visiblly,the expression quantity of BSH and DanK genes did not change significantly before and after the biofilm formation,and the expression of other two genes had increased.(4)The L.plantarum biofilm powder was prepared using spray drying,and the properties of bacteria powder are measured.The survival rate of plankton powder is only 1.02%.while the biofilm powder reached 50.99%.The acid producing ability of experimental group and control group changed a little before and after spray drying,the final pH is 3.4?3.5 after being cultivated 36 h.In conclusion,this experiment has concluded the optimum condition of L.plantarum SCP53 biofilm formation,and the environmental factors had a greater influence on the induction of biofilm formation.The increase of some gene expression after biofilm formation shows that environmental stress can induce the formation of biofilm,and film-forming strains have higher tolerance to various factors in the processing environment.The spray drying powder ofbiofilm strains bacteria also have certain fermentation characteristics,with a great significance in the industrial application.