| Cellulose is currently the most abundant natural organic substance in the world,and is widely used in textile,light industry,chemical industry,medicine,energy and environmental protection.Carboxymethylcellulose(CMC)a large number of carboxyl groups has the advantages of biosafety,biocompatibility and degradability,which can react the cationic polymer of chitosan(CS)based on polyelectrolyte complex and thus result in the formation of hydrogel.However,in view of the fragile mechanical property and the contradiction between its pH response and controllable release of the hydrogel,a balanced system is needed to alleviate the above contradiction.In addition,Bacillus subtilis natto is a beneficial bacteria producing functional proteins including nattokinase,and the stain can improve the equilibrium of human intestinal flora by inhibiting harmful bacteria.To this end,this present work takes CMC/CS/sodium alginate(SA)/calcium ion as the main matrix and controls the balance between CMC/SA and CS/calcium ion system.Scanning electron microscopy,infrared,and thermogravimetric were applied to characterize the beads.The results indicate that the balance between pH response and controllable release was achieved.A systematic study of the embedded Bacillus subtilis natto in the controllable release was systematically studied in artificial simulated gastric and intestinal fluids.The specific results are as follows:(1)Through pH response and electron microscopic,infrared and thermogravimetric microstructure analysis,the optimal carrier microsphere matrix components are CMC,CS,SA,and finally treated with calcium chloride.Furthermore,CMC/CS/SA carrier beads have good pH response.As the pH of the external solution increased from 1 to 7 and 10,the swelling rate increases from 102%to 117%and 122%,respectively.Besides,the carrier beads also have a good ability to embed Bacillus subtilis natto,with an embedding rate of 67.3%.In the simulated gastric juice,the shape remained unchanged while in the simulated intestinal fluid,swelling and rupture occured,releasing active Bacillus subtilis natto.(2)The component optimization results indicated that the optimal contents of the CMC,CS,SA and CaCl2 in the cellulose-based pH-responsive carrier are 1 wt%,0.5 wt%,1 wt%and 2 wt%,respectively.and the optimal addition order is CMC,CS,SA,and finally calcium chloride solidifies.The optimized beads have better internal structure and pH response,and the best release effect in gastrointestinal fluid.(3)The storage property of beads was investigated and the results indicate that the optimal storage condition for embedding Bacillus subtilis natto is to freeze-dry and store at 4?.Furthermore,the kinetic analysis of the release process of the embedded carrier in the intestinal fluid of Bacillus subtilis natto was carried out,and the three equations were fitted and compared.The results showed that the diffusion-dissolution model best fitted the release process of Bacillus subtilis natto from the beads.This indicates that the bead can corrode in the intestinal fluid,expressing a good pH response.Accordingly,the internal Bacillus subtilis natto release process is controlledIn this paper,a pH-responsive carrier with CMC/CS/SA/calcium ions as the main matrix was prepared through optimization of matrix components.It has good pH-sensitive characteristics,and the embedded rate of Bacillus subtilis natto is high and the storage time long.Bacillus subtilis natto released in the simulated intestinal fluid has high vigor meeting the requirement of probiotics in intestinal fluid.The prepared carrier has good pH response and slow-release performance.Meanwhile,the matrix material has safety and biocompatibility,and thus the bead has potential application in the field of medicine and health food. |
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