| Astaxanthin,one of carotenoid,is well-known as one of the strongest naturally antioxidant,with functions of anti-cancer,anti-aging,anti-wrinkle,improving human immunity and coloring,which can be widely used in food,drugs and cosmetics fields.Currently,natural astaxanthin is mainly produced by Phaffia rhodozyma and Haematococcus pluvialis.Although the content of astaxanthin is lower than that of H.pluvialis,P.rhodozyma has been widely investigated due to the advantages of fast growth rate,short culture period,simple culture conditions,no need for illumination and high-density culture.Astaxanthin accounts for a major proportion?more than 70%?of carotenoids from P.rhodozyma.At present,astaxanthin has not been widely used in the market,and its application is greatly limited by its small yield,unsafe extraction reagent,high production cost and instability.In this paper,strain mutation,cell disruption,fermentation of sugarcane bagasse hydrolysate as carbon source,astaxanthin embedding and stability of the astaxanthin complex were studied,which provides some reference for the further study and application of astaxanthin.First,the combination use of atmospheric and room temperature plasma?ARTP?and ultraviolet?UV?mutagenesis was studied,with 120?mol/L diphenylamine as mutant selection agent.Mutant Y1 was obtained from the selection plate and 54.38 mg/L of carotenoid was achieved with YPD as fermentation medium,which was 19.02%higher than that of the original strain.Carotenoid content of mutant Y1 was 5.38 mg/g,21.20%higher than that of the original strain.Then,ultrasonic and enzymatic hydrolysis was used to break cell wall and the parameters were studied.A green and simple extraction method was established,namely,ultrasonic disruption was conducted for 60 min,followed by enzymatic hydrolysis for 10 h,with enzyme loading of 64.6 FPU/g,leading to a pigment extraction rate of 96.01%.Using sugarcane bagasse hydrolysate as carbon source,the effects of nitrogen source and concentration on the growth and carotenoid synthesis of P.rhodozyma were studied by single factor experiment.The optimal medium was:sugarcane bagasse hydrolysate of 30 g/L,mixed nitrogen source of 6 g/L?yeast extract:urea=3:1?,magnesium sulfate of 0.5 g/L,and potassium dihydrogen phosphate of 1.0 g/L.P.rhodozyma cultured with the optimal medium as substrate at 22? and 220 rpm after 96 h,the biomass was 12.65 g/L,and the carotenoid yield was 88.57 mg/L.A simple process was established to encapsulate astaxanthin with zein and oligochitosan,forming astaxanthin/zein-OCH complex,with an encapsulation efficiency of 94.34±0.64%and an astaxanthin loading of 6.51±0.04 mg/g.The characterization of astaxanthin/zein-OCH complex was performed by Fourier transform infrared spectroscopy and microscope.Encapsulation obviously enhanced the UV-light and storage stability of the astaxanthin.At 4?,astaxanthin/zein-OCH complex showed the highest stability,with a minimum k(0.0097 week-1)and maximum half-life?71.4 weeks?.Moreover,when stored at25? after 4 weeks,the solubility of astaxanthin/zein-OCH complex was 40,73.9 and 90%in liquor,apple vinegar and rice vinegar,respectively,showing that the complex could be well dispersed in this three food systems.A prominent rise in DPPH-scavenging activity was observed in the three food systems due to the addition of astaxanthin/zein-OCH complex.The present work presents a simple astaxanthin encapsulation process to improve its UV-light and storage stability,showing potential applications in the food field. |
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