| Bifidobacterium is an important sort of probiotics. They have various of physiological effect forhuman being However, there are many factors affecting the viability of Bifidobacterium duringdownstream processing, storage and eventually digestion..Microencapsulation is one of most commonlyused method to protect probiotics from adverse conditions and to achieve intestinal release. Althoughalginate and protein are the main coating materials used for microencapsulation of probiotics, they havetheir own limitilations. So the remaining challenge is to overcome these limitilations posed by alginate andprotein and to further improve the protective effect provided by microcapsules. The improvedmicroencapsulation system have been developed based on alginate and protein, the mechanism ofprotective effect provided by microcapsules was disscussed. Meanwhile some reinforcement were adoptedto futher improve the protective effect.Alginate microspheres containing Bifidobacterium bifidum F-35prepared by emulsification/internalgelation were reinforced by blending with pectin or starch, or coating with chitosan or poly-L-lysine toprovide extra protection for the strain. The influence of these treatments on the size of microspheres,encapsulation yield (EY) and protective effect of microencapsulation on the cells was studied. Nodifference were detected in EY with different type of reinforcement, which was approximately43%-50%.The mean diameter of reinforced alginante microspheres ranged from117to178μm, reaching a maxiumvalue when starch was incorporated in the alginate matrix. It was observed that the protective effects variedwith the type of reinforcement. However, chitosan-coated alginate microspheres provided the bestprotection for microencapsulated cells in simulated gastro-intestinal tract and during one month storage at4℃, and this system could be the comparatively effective vector of bifidobacteria for intestinal delivery.Bifidobacterium bifidum F-35was microencapsulated into whey protein microcapsules (WPMs) by atransglutaminase (TGase)-induced method after optimization of gelation conditions. The performance ofthese WPMs was compared with that produced by a spray drying method (WPMs-A). WPMs produced bythe TGase-induced gelation method (WPMs-B) had larger and denser structures in morphologicalexaminations. Native gel and SDS-PAGE analyses showed that most of the polymerization observed inWPMs-B was due to stable covalent crosslinks catalyzed by TGase. The degradation properties of theseWPMs were investigated in simulated gastric juice (SGJ) with or without pepsin. In the presence of pepsin,WPMs-A degraded more quickly than did WPMs-B. Finally, survival rates of the microencapsulated cellsin both WPMs were significantly better than that of free cells and varied with the microencapsulationmethod. However, WPMs-B produced by TGase-induced gelation could provide better protection formicroencapsulated cells in low pH conditions and during one month of storage at4oC or at ambienttemperature.Bifidobacterium bifidum F-35were encapsulated into microcapsules with four types of protein-basedcoating material, soy protein isolation (S), whey protein isolation (W), sodium caseinate (S), gelatin (G)through transglutaminase-induced emusification/gelation method. The survivability of microencapsulatedcells in the four protein-based microcapsules was conducted in simulated gastric juice (SGJ) with orwithout pepsin. SPI-based microcapsules provided the best protection for microencapsulated cells in alltreatments. As for Bifidobacterium bifidum F-35, in SGJ with or without pepsin, the the D-value ofencapsulated cells in these four protein-based microcapsules were31.7,24.2,22.7,18.7and124.3,103.5,97.6,47.8min, respectively. Additionally, this research also investigated some physical properties of theseproteins for difference in protective effect on encapsulated cells in SGJ without pepsin. The result showedthat emulsion stability was S> C> W> G; gel strength was G>S>C>W; permeability to SGJ wasW>S=C>G, buffer capacity was W>S=C>G. It could be deduced that buffer capacity have great influenceon the protective effect in low pH condtion, other potential reasons for difference in the protective effectinclude difference in permeability of protein gels, emulsion stability and gel strength can also affect theprotective effect.Taking survival rate of Bifidobacterium bifidum F-35in2-h simulated gastric juice, particle size ofmicrocapsules, the process conditions of coating alginate on whey protein microcapsules were optimalized.The optimum coating conditions were established: pH5.5alginate solution,0.5%concentration of alginatesolution,0.07M concentration of CaCl2, and500rpm agitation rate. The particle size of microcapsules were132.6μm, the survival rate of Bifidobacterium bifidum F-35in simulated gastric juice was improved to14.5%at the optimal coating condition. The study also showed that the alginate could be effectively coatedon the surface of whey protein microcapsules. The outer alginate membrane could significantly reduce thedegradation role of pepsin on whey protein matrix. Beside, the coated microcapsules could delay therelease rate of Bifidobacterium bifidum F-35in simulated intestinal juice, but they provided the best protecti on for microencapsulated cel ls in sequential si mulated gastrointest inal j uice, t he survival rate wasup to51%。... |
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