| Tributyrin,a short-chain fatty acid ester,principally functions to maintain the intestinal flora balance,prevent enteritis,and enhance immunity,which is widely used in food,medicine,feed,and other fields.However,limitations,like unpleasant odor,poor fluidity,and poor water solubility,narrow down its application.Typically,one can resort to encapsulation for the improvement of functionalities.Cyclodextrin is one of the commonly used encapsulation wall materials.Its enzymatic production process often requires complexing agents to form inclusion complexes with cyclodextrin to maximize the yield of cyclodextrin.Thus,in this study,tributyrin acted as the complexing agent that had been creatively incorporated during the enzymatic synthesis of cyclodextrin,which promoted the yield of cyclodextrin and encapsulated tributyrin simultaneously to eliminate some of its inherent drawbacks.Tributyrin microcapsules were formed using cyclodextrin products as the wall material.Further,the preparation process had been investigated systematically to obtain cost-effective tributyrin microcapsules with excellent performance,which could provide a new idea for the microcapsule preparation.The main contents of this paper are as follows:Firstly,the process of synchronous encapsulation of tributyrin during enzymatic synthesis of cyclodextrin by ?-cyclodextrin glycosyltransferase from Bacillus circulans was established.The cyclodextrin yield analysis showed that the total yield of cyclodextrin was increased from 25.90% to 44.10% after adding 10%(w/w)tributyrin,increasing by 70.27%.The yield of different cyclodextrin increased in various degrees,alluding to the complexing interplay between tributyrin and cyclodextrin.?-cyclodextrin content topped the list by 88.26% among them.Here,the tributyrin microcapsule was obtained by the preparation process including shearing,homogenizing and spray-drying,which confirmed the feasibility of this method.Secondly,the preparation process of tributyrin microcapsule was optimized by studying the effects of various parameters during encapsulation,emulsification,and spray-drying on the final microcapsule properties.The optimal parameters of encapsulation with viscosity and cyclodextrin yield as indicators were the liquefaction enzyme amount being 2 U/g,the liquefaction time 30 min,the cyclization enzyme amount 2 U/g,the cyclization time 10 h,the cyclization temperature 50°C,and tributyrin better being added at the beginning of the cyclization reaction(0 h);Besides,the optimal parameters of emulsification with emulsion stability as an indicator were the emulsifier amount being 2%,the homogeneous pressure 35~40 MPa,and the homogenization process better repeating by 3 times;Also,the optimal parameters of spray-drying with encapsulating efficiency and retention as indicators were the core-to-wall ratio being 1:1(w/w),the inlet air temperature 180°C,the outlet air temperature 80°C,and the feed temperature 50°C.Under the optimal conditions,the yield of cyclodextrin was 48.08%,the highest tributyrin content of microcapsule was 42.88%,the encapsulation efficiency and retention were 76.70% and 90.05%,respectively,which was significantly better than the sample without optimization.Go a step further,the property of tributyrin microcapsule prepared under the optimal process parameters was evaluated.Respectively,the structure,dispersibility,odor performance,rehydration property,and delivery property were characterized by micro-morphology observation,particle size distribution,headspace phase analysis,emulsion stability determination,and in-vitro simulated release.The results indicated that the microcapsule was hollow and spherical,with some shrinkage,which had a good dispersibility and varied in particle size(1~10 ?m).The microcapsule prepared by enzymatic cyclodextrin synthesis system could significantly reduce the unpleasant odor,and had better reconstituted emulsion stability(93.21%)and a higher cumulative release in the small intestine(65.50%)compared with other wall materials based tributyrin microcapsules and commercial silica-based tributyrin powder.Cyclodextrin did help to reduce unpleasant odor and increasing emulsion stability in the system.Finally,the encapsulation mechanism,both conformation and process,was analyzed through inclusion complex stability constant,molecular simulation docking,nuclear magnetic resonance,and thermodynamic analysis.Results showed that the inclusion complex stability constant of tributyrin and ?-,?-,?-cyclodextrin were 251.13,585.59,69.30 L/mol,respectively.The constant determined the interplay between host and guest molecule,and related to the increasing degree of cyclodextrin yield.Molecular simulation docking suggested that tributyrin was encapsulated with cyclodextrins in different conformations,and the closest inclusion was observed with ?-cyclodextrin.Moreover,thermodynamic analysis showed that the inclusion phenomenon was spontaneous and driven by enthalpy.1H NMR results confirmed the diversity of conformations.Based on the analysis of inclusion mechanism and structure,an encapsulation model was constructed.It was speculated that the tributyrin was encapsulated by cyclodextrin hydrophobic cavity and microcapsule wall layer formed during spray-drying.This double structure led to better performance of tributyrin in solubility and bioavailability. |
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