Studies On The Selection Of Kojic Acid Producing Strain And Process Optimization

Kojic acid, a weak acid compounds is widely used, chemical name is5-hydroxyl-2-hydroxymethyl-1,4-pyrone. It has the ability of inhibiting tyrosinase,bacteria and oxidase as well as the effect of chelating to metal ions. As a new typeof food and cosmetics additives, Kojic acid has been applied to the field of food,chemistry and medicine. It has attracted the domestic and foreign research interests.But now, Kojic acid fermentation production technology is still not mature enoughin domestic and foreign, on the market, The number of Kojic acid are providedlittle and expensive, so we must vigorously carry out the production of Kojic acidfermentation.In this paper, a strain was screened from five strains, And to it for startingstrain, a mutant of high-yield Kojic acid producing was obtained after treated withultraviolet light and N+implantation respectively, at the same time the fermentationprocess of Kojic acid to be researched, and research some factors that influence ofKojic acid synthesis, and the extraction of Kojic acid was also studied, Finally,50Lfermentation tank experiment of high yield strain was studied.An excellent Kojic acid-produciton strain Aspergillus oryzae CICC-2336wasscreened from five strains, and its yield of Kojic acid reached12g/L.Aspergillus oryzae CICC-2336was mutated by ultraviolet light and N+implantation respectively, First, Aspergillus oryzae UV7was obtained after treatedwith ultraviolet light, The condition was that15W UV light exposure40s, thediatance was30cm. and the yield of Kojic acid reached18.50g/L. Secend,Aspergillus oryzae N11whose Kojic acid yield uped to24.12g/L was obtained fromthe staring UV7which was mutated by N+implantation. The condition wasirradiated with10keV and ion implantation dosage10×1014ions/cm2·s.Glucose and yeast extract was determined as the most proper carbon andnitrogen source through the single-factor experiment by Aspergillus oryzae N11.Plackett-Burman design was used to evaluate the effects of medium components onthe yield of Kojic acid by Aspergillus oryzae N11. The result showed that: glucose,yeast extract and K2HPO4were the most important factors that influence the yieldof Kojic acid. Based on the experimental results, the path of steepest ascent wasundertaken to approach the optimal region of these factors, central composite design and response surface analysis were subsequently employed for furtheroptimization. The optimal medium for Aspergillus oryzae N11was obtained, whichwas composed of glucose10.87%, yeast extract0.26%, K2HPO40.06%, KCl0.05%，MgSO4·7H2O0.05%, and its yield of Kojic acid reached23.34g/L.Factors that affect the decolorization were obtained through the single-factorexperiment by Aspergillus oryzae N11. And the results were that6%activatecarbon, bleaching temperature80℃, bleaching time45min, and in this conditions70.34%discoloration rate and the90.12%Kojic acid yield was obtained. After theremoval of the cationic impurity with cation exchange resin, Kojic acid crystal wasobtained by the way of direct concentration crystallization. Finally,72.63%Kojicacid yield coefficient was obtained and its purity was95.54%.The fermentation was studied in fermentation tank, to investigate thefermentation ability of N11, After fermentation conditions commissioning AndKojic acid was25.23g/L, after fermentation7d under the comdition of15%(v/v)inoculum,30℃, speed120r/min and minute ventilation10L/min.