Isolation, Modification And Application Of Aureobasidium Melanin

Aureobasidium pullulans can be used as a strain to produce a series of substances,such as amylopectin,melanin,extracellular enzyme,etc.,are excavated and applied to scientific research and industrial production.Melanin is a kind of phenolic substances or indole polymerization of the formation of biological macromolecules.It can be combined with the metal,not afraid of ultraviolet light,remove free radicals and so on.So melanin is diffusely used in medicine,chemistry,cosmetics,farming,eating and other areas.In this paper,by comparing all the extraction methods of melanin in the literature,the extraction of melanin,the fermentation components and conditions were optimized.The water insolubility of Aureobasidium pullulans' melanin makes it great limit of the application.Therefore,the use of a variety of amino acids to modify the melanin to get lysine-melanin which slightly soluble in water,and to explore its stability with the original melanin.Aureobasidium pullulans' fermentative solution is thick and dark for ink preparation,not only make ink color bright,but also has waterproof,environmental protection and other good points.Conclusion as below:(1)The effects of mang factors in the extraction of the combination method of lye extraction and acid deposition with acid and ethanol deposition were optimized by single factor and response surface.These factors include ethanol addition,ethanol concentration,NaOH concentration,heating temperature and acid sinking time.The results show that when the ethanol content was 48.9 m L,the ethanol concentration was 60%,the NaOH concentration was 2.65mol/L,the heating temperature was 70?,the acid sinking time was 8h,the yield of the melanin of Aureobasidium pullulans was 0.73 ± 0.002 g/L.(2)The conditions of fermentation medium were optimized by single factor and response surface:200 g/L of potato,20 g/L of glucose,20.26 g/L of ammonium sulfate,20 mg/L of tyrosine,KH2PO4 0.3 g/L,pH was 7.0,the culture temperature was 28?,the inoculation amount was 5 mL,the culture time was 116 h,and the yield of melanin of Aureobasidium pullulans reached a maximum of 1.23 ± 0.005 g/L.(3)The melanin was modified by twelve amino acids.The results showed that lysine-melanin can be slightly soluble in water,the solubility in distilled water at 37°C was 5.46 g and the color price was 214.0 U/m L.The structure was analyzed by scanning electron microscopy,ultraviolet spectroscopy,infrared spectroscopy and magnetic resonance imaging.The results showed that there are some amino acid molecules and melanin binding in lysine-melanin.But there are still some amino acids without chemical reaction and attached to the melanin surface.The highestabsorption peak of melanin in the ultraviolet region was 216.5 nm.The structure contains indole groups,more aliphatic C-H and amide groups.The primary amino group on the 2-position of lysine binds to the carboxyl group of the melanin of Aureobasidium pullulans to form an amide,which makes the melanin can dissolve in water.(4)To explore the stability of melanin and lysine-melanin against light(sunshine,ultraviolet),heating temperature,acidity,H2O2,Na2SO3,heavy metal ions and a variety of substances added to the food.The results showed that lysine-melanin in the light,less than 60?,strong oxidant environment is stable,can be dissolved in the pH ? 4,easily precipitated in the strong acid and more stable in the presence of food additives.Lysine-melanin in the presence of Mg2+,Ca2+ is unstable,other metal ions are more stable,and the stability of the melanin of Aureobasidium pullulans has a great similarity.(5)The Aureobasidium pullulans fermentation broth with bone glue,high color lamp black,sodium dodecyl sulfonate,sodium benzoate and sandalwood are equipped with a waterproof ink of environmental protection.Fermentation broth of the Aureobasidium pullulans is black and bright because it contains melanin.Due to containing pullulan polysaccharides,poly malic acid,sorbitol and other substances,the fermentation broth is sticky and smooth.Therefore,in the process of configuring the ink,compared to the traditional method,the ink reduces the use of chemical reagents,greatly reducing the toxicity and environmental pollution.Because of the film properties of pullulan polysaccharides,so that the ink can be waterproof.Compare with a commercially available ink,the ink which obtained by Aureobasidium pullulans fermentation liquid mixture formation is brighter,waterproof,can also be used in low temperature,and will not degenerate.The diffusibility of the disposable ink is inferior to the commercially available ink so it can be diluted in the course of use.