Study On Surface Hydrophobicity And Auto-aggregation Ability Of Probiotic

Bacterial surface hydrophobic characteristics means that the unstable stateof the bacteria in the polar water, which lead to a series of changes inre-distribution and arrangement of the bacteria. Auto-aggregation ability meansthe self-aggregation phenomena of bacteria as a result of a large and fastbreeding in the training process. Hydrophobicity and auto-aggregation ability aretwo of the important factors affecting the two-phase reaction, and they arerelevant to a variety of adhesion phenomena. The strength of bacterial surfacehydrophobicity and the auto-aggregation ability depend on the number ofnon-polar groups, the surface proteins, fimbriae, lipoteichoic acids andcapsular of the bacterial surface.In this experiment, six highly representative of probiotics were studied.Firstly, to determine the best growing conditions, their growth curve and acidproduction were draw. Then the bacterial surface hydrophobicity were analyzedby bacteria adhesion to hydrocarbons. The results show that the six testedbacteria were incubated for10h in anaerobic37℃,OD of the medium was themaximum and pH was the minimum. And the surface hydrophobicity of thetested strains are: Lactobacillus acidophilus (90.02%)> Lactobacillusrhamnosus GG (30.03%)> Lactobacillus casei (26.65%)> Lactobacillusplantarum (24.01%)> Lactobacillus bulgaricus (17.23%)> Streptococcusthermophilus (8.67%). The surface hydrophobicity of Lactobacillus acidophiluswas significantly higher than the other five bacteria. In addition, Lactobacillusacidophilus was selected to analyze the influencing factors of the surfacehydrophobicity of probiotics. Through the single factor test analysis, theconclusion which was that the surface hydrophobicity had a certain relationshipwith culture time, temperature, pH, bacterial concentration, Ca2+, proteases,oligosaccharides, sodium periodate and LiCl was obtained. Among them, whenthe incubation time, temperature, pH, bacterial concentration, Ca2+and sodium periodate were8～10h,37～41℃,4.0～5.0,0.5～0.6,0～5mmol/L and0～10g/L, which could promote the cell surface hydrophobicity. And the proteaseand LiCl had a strong inhibitory effect on the surface hydrophobicity ofLactobacillus acidophilus. This indicated that the cell surface protein played akey role on its surface hydrophobicity. In order to improve the surfacehydrophobicity of Lactobacillus acidophilus, pH, cell concentration (OD) andtime were taken as significant factors for optimization with Box-Benhnkencentral composite experimental design. The results showed that the best valuesof pH, OD and were4.22,0.40and11.05h, when the surface hydrophobicitycould be increased to94.53%.Secondly, the auto-aggregation ability of the six tested bacteria were studied.The results of analysis were that the bacteria were standed after150min, theauto-aggregation ability of Lactobacillus acidophilus was53.26%, significantlyhigher than the other five bacteria at all the experimental conditions,Lactobacillus rhamnosus was35.49%, second to Lactobacillus acidophilus, andthe auto-aggregation ability of Streptococcus thermophilus was15.75%. Inaddition, the auto-aggregation ability of Lactobacillus bulgaricus, Lactobacilluscasei and Lactobacillus plantarum were19.28%、25.76%and18.53%, at a lowlevel. In addition, Lactobacillus acidophilus was selected to analyze theinfluencing factors of the auto-aggregation ability of probiotics. The resultsshowed that the auto-aggregation ability of Lactobacillus acidophilus wasaffected with the incubation time, temperature, protease, and LiCl. And proteaseand LiCl showed strong inhibition to the auto-aggregation ability ofLactobacillus acidophilus. Among them, when the incubation time andtemperature were10h and41℃, the baceria had the strongestauto-aggregationbility. However, when Lactobacillus acidophilus was processedby the protease and LiCl, the auto-aggregation ability was significantly inhibited.This indicated that the auto-aggregation ability were closely related withbacterial surface proteins.Dynamics factors, environmental factors and cell surface properties ofmatter of probiotics were studied. And the species differences in surfacehydrophobicity and auto-aggregation ability of the probiotics were obtained. Inaddition, the main affecting factors of the cell surface hydrophobicity and auto-aggregation ability were growth phase, pH, bacterial concentration,temperature, metal ions, enzymes, bifidus factor, oligosaccharides, and chemicalsubstances. This provides a basis to the mechanism of action of probiotics, andoffers new ideas and theoretical experience in the development of highperformance probiotic products.