| Kojic acid is a kind of natural weak acid compounds and has special physiological activity,its molecules contains phenol hydroxyl, hydroxyl and carbonyl groups and so on. It can be synthesized into a variety of derivatives, and act as catalyst of some chemical reactions. So Kojic acid is an important chemical raw materials and intermediate. According to recent studies, it can inhibit tyrosinase activity thus inhibit the formation of melanin as well as the effect of tyrosinase, so it has good antisepsis effect. Therefor Kojic acid is with wide application prospect in medicine, food, cosmetic, agriculture and other fields.In this paper, Aspergillus oryzae HD0 was as a starting strain, then be treated with microwave-ultraviolet- atmospheric pressure plasma composite mutation. At first, it was treated with microwave,the condition was that output power 700 w, pulse frequency 2450 hz, irradiation time 50 s, a mutant of high-yield Kojic acid producing HDM11 was obtained. its yield of Kojic acid reached 25.3g/L increased by 59.12% Comparing with the original strain HD0(yield is 15.9 g/L); HUV30 was obtained after treated with ultraviolet light, The condition was that 20 W UV light exposure 3min, the distance was 30 cm, and the yield of Kojic acid reached 38.9g/L increasd by 144.6%. HAP2 was obtained after treated with ARTP, the condition was that 120 W mutation power, High purity helium ventilation 10 SLM, the distance was 2mm, exposure 100 s, and the yield of Kojic acid reached 58.87g/L increased by 270.2%.This thesis studies the influence of fermentation condition on the acid production of high-yielding strains. First is the single-factor experiment. The accelerant is absolute ethyl alcohol with the volume fraction of 2%. I choose those factors which affect significantly and optimize the condition of culture by orthogonal test. The condition after optimization is as following: p H 6.2; Rotation rate of shaking table: 180 rpm; Fermentation Time: 7d; Liquid Leading: 50ml; Temperature: 30 ℃; Inoclum Amount: 10%.At the same time this single-factor experiment shows that the concentration of glucose, yeast extract as well as KH2PO4 has marked impact on acid producing. I optimized the three constituents through Response Surface Method in order to see their effect on the fermentation of kojic acid. I did multiple regression statistic analysis by SAS and the regression coefficient of the fitted equation is 0.9514. This result shows that this model applies to the theoretical speculation of kojic acid fermentation. The constituents after optimization are: glucose 9.95%, yeast extract 1.0065%, KH2PO40.0576%,Mg SO40.06%. Under this condition of culture medium and fermentation, the output of kojic acid reached 72.32g/L which was 22.85% higher than the output before optimization.Preliminary exploration of kojic acid extraction process was that decoloring the solution by activated carbon and cation exchange resin, to determine the optimum decolorizing activated carbon dosage was 1.2%,temperature was 70 ℃,decolorization time is 30 min. Eventually,the decolorization rate was 82.74%, the yieldof kojic acid was 78.36%,the color of the solutionhas becomepale yellownear colorless which was observed by naked eye at this time.The decolorization kojic acid solution was recrystallized.The result of IR analysis and HPLC analysis on the crystallization results shows that crystalline substance is kojic acid, the crystalline content is 99.1%. |
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