| y-Polyglutamic Acid(?-PGA)is a kind of extracellular products synthesized by microorganisms.It was consisted of monomer amino acid with high polymer and had excellent moisture retention,biocompatibility and biodegradable.Therefore,?-PGA and its derivatives had been of great interest in a broad range of industrial fields such as cosmetics,agriculture,medicine and food and so on.At present the purification and extraction process is the biggest factor affecting the industrialization of ?-PGA.We attempted the PEG/(NH4)2SO4 aqueous two-phase system to extract ?-PGA from the fermentation liquid and adopted ?-PGA and CS as the wall material to manufacture the sustained-release cinnamaldehyde nanocapsule and simulated its application in the tobacco cigarettes.In this study,an aqueous two-phase system consisting of polyethylene glycol(PEG)and(NH4)2SO4 was used to extract ?-PGA from the fermentation liquid treated by centrifugation.We identified three factors namely PEG molecular weight,PEG concentration,(NH4)2SO4 concentration and pH values of the pretreatment fermentation liquid that have a large impact on extraction efficiency.And the multivariate quadratic regression model using extraction rate and distribution coefficient as the response variable was established based on a Box-Behnken experimental design involving three factors at three levels each and subjected to response surface analysis.The results showed:The multivariate quadratic regression model was significant(p<0.0001)when setting the extraction ration as response value and the optimal extraction condition was the concentration of PEG1000 and(NH4)2SO4 was 24.61%and 15.97%respectively,the pH value of the fermentation liquid was 6.02 and the temperature of the system was 25?.Under this condition,the maximum extraction ratio was 81.44%in theory and the relative error was 0.32%for the actual value was 81.18%.The multivariate quadratic regression model was not significant(p=0.082>0.05)when setting the partition coefficient as response value.Based on the optimized extraction conditions,the purity of the product was 99.07%and the hydrolysis product was a single glutamic acid.The molecular weight of the product was not a definite value(above 70kDa)but a wide distribution.Then the controlled release cinnamaldehyde nanocapsule was made by poly electrolyte layer by layer self-assembly method at normal temperature and pressure with ?-PGA and CS as wall material.When the concentration of ?-PGA and CS were lg/L and the volume ratio were 1:1 and the concentration of cinnamaldehyde in the system was 0.7g/L,the Z-Ave,PDI,EE and LE of the cinnamaldehyde nanocapluse were 387nm,0.308,64.1%and 44.8%respectively.Studies on the release property of the nanocapluse in 15 days showed the odor characteristics of the core was stable within 0-8 days.But it was gradually fading out within 9-15 days.Infrared spectroscopy tests showed there were no chemical groups formed after the core embedded and the wall material to core was just a simple physical encapsulation.The thermogravimetry analysis showed the pyrolytic temperature of the embedded cinnamaldehyde increased 7? and the wall material played a good protection on the core.The results of the scanning electron microscopy showed the empty shell ?-PGA/CS nanocapsule owning the porous structure that provide a shelter for the core.Through the comparison of the transfer rate ratio of cinnamaldehyde in nanocapsule state or not,the sample added cinnamaldehyde nanocapsule did not show a better release uniformity and intelligent response to the mainstream smoke.The results of sensory evaluation showed the optimum addition amount of the cinnamaldehyde nanocapsule was 1.5%-2.0%of one cigarette quality.At this point the bad smell in the mainstream was masked and the smoke quality was improved remarkably and the smell was satisfied. |
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