Protoplast UV-mutagenic Breeding Of A Plectania Strain And Its Melanin's Characters And Structure

In this paper,isolation and selection of the melanin-producing strains,breeding the high melanin-producing strains by mutation,optimizing the mutation strain fermentation conditions,the kinetics model,extraction of the intracellular melanin, phy-biology characteristic and biological function of the melanin were studied and identification of the melanin.The resultes as followes:(1) A high melanin-producing strain was isolated from the fruit-body collected from Huangshan Mountain,China,and identified as Plectania sp.(2) The highest yield of protoplasts conditions were obtained by using 2.5% snailase digested for 3 hours at 33℃.The best icduced conditons were under the UV linght at the distance of 30cm irridated 20s,the mutant strain which the yield of melanin increased 10.03%and the biomass increased 11.33%.The optimum fermentation conditions of mutant were as follows:glucose 2.5%,K₂HPO₄ 0.05%, MgSO₄ 0.03%,monosodium glutamate 0.5%,yeast extract 0.4%,pH 6.5,25℃,time 8d。(3) The data showed the fermentation type of Plectania YM421 was related to the growth followed the Luedking-Piret.The biomass and melanin highest production was at the concentration of the sugar was 2.5%.(4) Extraction the intracellular melanin of Plectania YM421 by adjust pH with hot water,and the resultes showed that the optimization conditions were as followes:the temperature was 90℃,time was 4h,the ratio of solid to liquid was 1:200 and pH was 12.(5) The resultes of the stability of the melanin indicatied that the melanin was stable to pH≥6 and under indoor light,but deposit while pH≤5,also the stablitity decreased under outdoor-exposure and ultrauilet.Sucrose,glucose,lactose,maltose, Na₂SO₃,sodium benzoate and sodium citata citrosodine had the function of color increase or color preservation to melanin,while H₂O₂,citric acid and Vc decreased its stability.The reducing power of the melanin of Plectania YM421 was increased with the concentraction increaing.The scavenging activity of melanin on hydroxyl radical was 50%at 350μg/mL.The melanin can highly against UV light irradiation,the oxygen radical absorbance capacity of phosphatidylcholine was 56%at the concentration of melanin was 80mg/mL,and it can highly inhibiting oxidative activity of bean oil.(6) The results of the prilimilary study of the melanin structure indicatied that the melanin contains -OH,-NH,alkane,aromatic circle and other functional groups,the structure regarded as benzoquinones and aliphatic,The molecular weight of melanin is 485。...