The Research On Arabinoxylan-alginate Microencapsulated Lactobacillus Plantarum

Probiotics have a variety of healthy benefits. However, in order for probiotics to exert these beneficial effects, they must be able to tolerate the acidic conditions of the stomach environment as well as the bile in the small intestine. Microencapsulation is one of most commonly used method to protect probiotics from adverse conditions and to achieve intestinal release. As coating materials, alginate has been widely used to encapsulated probiotics, but some studies indicated that encapsulated with alginate alone can not provide probiotics with ideal protective effects.Due to the porous structure, aqueous environment and dietary fiber nature, arabinoxylan(AX) gels have potential applications for colon-specific therapeutic molecule delivery. In addition, prebiotics and health related effects of AX have been previously demonstrated. It has been also reported that cross-linked AX can be degraded by bacteria in the intestinal microbiota. However, there is no information available concerning the capability of AX gel to entrap probiotics.So in this research, L. Plantarum was encapsulated in the beads made from arabinoxylan(AX) and Sodium alginate(SA) by the extrusion technique. Encapsulation yield(EY) and protective effect of incorporated microencapsulation on the probiotics were studied. Effects of co-encapsulation of L. Plantarum with arabinoxylooligosaccharides(AXOS) on AX-SA matrix were also analyzed.1. WEAX, WUAX, AXOS were prepared and the main component of them were determined. The relative weight-average molecular weight(Mw)of WEAX and WUAX were1.0×105 and 2.5×105 respectively. Ferulic acid(FA) content of WEAX and WUAX were 2.23μg/mg and 1.78 μg/mg respectively. The ratio arabinose to xylose(A/X)of WEAX was 0.63,while the A/X of WUAX was 0.56. WUAX were hydrolysised by Xylanase, the results showed that the Mw of AXOS varied from 2.1×104 to 4.5×104.2. Arabinoxylan gelation process is governed by the establishment of both covalent(di-FA, tri-FA bridges) linkages. AX gelling properties were related to extraction method as well as FA content. Entrapped L. Plantarum does not significantly affect the arabinoxylan gel ability.3. Characters of the microcapsules without L. Plantarum. The result indicated that AX entangled with SA macromolecular chains to form interpenerating network structure and the microcapsules mechanical strength of the network was enhanced.4. L. Plantarum was entrapped in the beads made from AX and SA by the extrusion technique. EY, acid-resistance, bile salt-resistance and controlled release of WUAX-SA beads were investigated. The results showed that comparing with SA encapsulated L. plantarum, theWUAX-SA beads could significantly increase the EY and the number of survival L.plantarum in simulated gastric juice or high bile solution. After exposed to the simulated gastric juice(2 h), comparing with SA beads, the survival rate of L. plantarum of 6%WUAX-SA beads increased 29.04%. WUAX-SA beads effectively prolonged its release upon exposuring to intestinal juice. L. plantarum were released completely when WUAX-SA beads were incubated in intestinal juice with xylanase. With the increase of enzymes concentration,the L. plantarum releasing rate inereased. The result showed that WUAX-SA beads have colon-specific property.5. Effect of AXOS on EY, acid-resistance, bile salt-resistance and controlled release of beads were studied. The results showed that the prebiotics had significant effects on EY and the resistance to acid and bile salts. Addition of AXOS( Mw: 2.1×104, 0.5%), the EY of beads was 85.4%.After exposed to the simulated gastric juice(2 h), the survival rate of beads maintained 79.03%.6. The stability of freeze-dried beads were studied. The results showed that after stored for one month at 4℃, the number of survival cells of SA beads decreased 0.98 log, while the number of living cells in WUAX-SA and WUAX-SA-AXOS microcapsules remained initial levels. After stored for two months at room temperature, the addition of AXOS could significantly enhanced L. plantarum storage stability.