Study On The Extraction, Purification And Encapsulation Of Astaxanthin From Antarctic Krill Shell

Astaxanthin is a carotenoid oxygenated derivative with a lot of biologicalfunctions including antioxidation property, anti-cancer activity and enhancingimmunity activity. And natural astaxanthin has stability, more effective functions,better applications and safer compared with combinations of chemicals, Extractingnatural astaxanthin from crustacean shells is becoming a new research hotspot formore and more scientists. The Antarctic krill as the key organism in the southernocean, abundant and contains astaxanthin. Antarctic krill needs to be urgentlyexploited and utilized.Antarctic krill shell has been used as experimential material, the technology ofastaxanthin extraction based on the method of enzymolysis combined with organicsolvent has been studied. Use extraction rate of astaxanthin as an indicator, Responsesurface methodology (RSM) showed that extractioned the ratio of krill shell wetweight to dichloromethane at1:5g/mL, shaking at the constant temperature (30℃) for7h, and extracting for2times, the yield of total astaxanthin is131.56μg/g. In order tofurther study on the extraction rate, papain is used for enzymolysis before extractingby dichloromethane and a response surface experiment with4factors and3levels isdesigned. It is showed that the optimal conditions are hydrolyzed pH is6.0,temperature is54℃, extration time is88min, E/S is2.00%, The yield of totalastaxanthin has reach up to145.04μg/g, which is10.25%higher than the yieldwithout the enzymatic extraction.Astaxanthin mainly exists in the form of ester in solution, in order to increase theconcent and purity of free astaxanthin, it is necessary to explore the methods ofisolation and purification of astaxanthin esters. Using KOH-C2H5OH magneticstirring for saponification reaction. AB-8was selected firstly in the technique to separate astaxanthin, then measured by high performance liquid chromatography(HPLC). Finally, the yield of free astaxanthin is369.97μg/g, which is83.3%higherthan the rate before saponification. The purity of the collected free astaxanthin is94.58%by high performance liquid chromatography (HPLC).As astaxanthin is susceptible to external factors such as light, heat and metallicions, so Nanotechnology has been introduced to improve the stability of astaxanthin.The lecithin and chitosan were well-dispersed in aqueous media, and formedself-aggregated nanoparticles by probe sonication. Taking the mean particle size ofnanoparticles as the response, the response surface methodology was adopted tooptimize the ultrasonic emulsification parameters. The optimum process wasdetermined as follows, lecithin/chitosan rate is20:1(w/w), ultrasonic time is16.0minand Tween-80emulsifier concentration is1.5%(w/v). The zeta potential ofnanoemulsion’s surface is+39.6mV detected by granulometer, which can prove thatnanoemulsion is the better carrier. The mean particle size of nanoparticles is121.34nm under the optimized conditions. The morphology of these nanoparticleswas sphere observed by transmission electron microscopy (TEM).The grain diameter of Astaxanthin has increased when entrapped into thelecithin/chitosan nanoparticles and its zeta potential is more than+30mV.Astaxanthin-nanoparticles were sphere in shape and equally distributed observed byTEM. With the increasing input of astaxanthin, the mean grain diameter and drugloading ratio have increased but encapsulation efficiency has decreased. The in vitrorelease experiment of astaxanthin-nanoparticles show that astaxanthin is susceptibleto pH. It is faster released in low pH value and is good for preserve in pH7.4.Stability experiments revealed that a notably slower degradation rate was observed forthe encapsulated astaxanthin, while free astaxanthin was subject to rapiddecomposition. Deoxidation and Antioxidant experiments indicate thatnanotechnology can remain deoxidation and antioxidant activity of astaxanthin effectively. Experiments revealed that astaxanthin-nanoparticles should be stored inPBS (pH7.4) at low temperature.