| Kojic acid is a kind of organic acids with antibiotic, food color-protection and colorants, antioxidation, skin whitening and inhibit tyrosinase and other biological activity, which was widely used in food, cosmetics, medicine and agriculture etc. In recent years, the demand of kojic acid is increasing. Howere, only a few institutions engaged in kojic acid production and research in domestic, the technology is relatively backward, the higher import price severely limits the application of kojic acid. The main problem of kojic acid production is long fermentation cycle, low productivity, higher cost of production and other issues. So the main research direction of kojic acid production is optimize the fermentation medium and conditions or uses inexpensive raw materials, in order to improve production efficiency and reduce the cost of production.This article use Aspergillus oryzae (Aspergillus oryzae) GIM3.423as Kojic acid producing strains, sugar cane as raw materials. The influence of sucrose concentrations, nitrogen source, mineral salts and ethanol on yield of kojic acid and biomass were studied. Though single factor test and orthogonal experimental, the optimum medium was determined as follow:Sucrose8%, yeast extract0.3%, KH2PO40.1%, MgSO4·7H2O0.05%, KC10.05%, initial PH7.0. Under these conditions, Kojic acid finial concentrations can be up to14.91g/L, increased2.2times than before the optimization, conversion rate is21%.Shaking flask fermentation were optimized by using single factors test, the optimum conditions was identified as follow:temperature30℃, liquid-loading capacity60mL/250mL, revolution200r/min, seed age6h, the volume of inoculation about10%, fermentation cycle13day.Based on the previous research, the kinetics for kojic acid batch fermentation by Aspergillus oryzae (Aspergillus oryzae) GIM3.423was studied. Through the optimal parameters estimation and nonlinear fitting method, kinetic models were proposed by using the Logistic equation for cell growth, the Luedeking-Piret equation for kojic acid production and the Luedeking-piret/like equation for sucrose consumption, the correlation coefficient R2respectively,0.9893、0.9861and0.9891. So the three models provided a reasonable description for cell growth, kojic acid production and sucrose consumption, provided theoretical basis for studying the enlargement experiment and industrial production automation control.Kojic acid production by immobilized Aspergillus oryzae in calcium alginate beads and polyurethane foam (low density sponge) were investigated, and the immobilize condition was identified though single factor test as following:(1)calcium alginate immobilize condition:Sodium alginate2%, CaCl23%. Calcium alginate beads was made in this conditions, the volume of inoculation about10%, the fermentation period is2days shorter than free Aspergillus oryzae fermentation, the final kojic acid concentration was14.911g/L,1.223g/L more than free Aspergillus oryzae fermentation, improved by8.94%than free Aspergillus oryzae fermentation in3rd batch fermentation,(2)Polyurethane foam immobilize condition:Polyurethane foam size:2mmx2mmx2mm, the volume of inoculation about1.0g/60mL, fermentation period is13days, just like free Aspergillus oryzae fermentation, finial Kojic acid concentrations up to15.426g/L, improve by12.73%than free Aspergillus oryzae fermentation in3rd batch fermentation.Feasibility of molasses as raw material of Kojic acid production was studied in this chapter, Aspergillus oryzae was immobilized by polyurethane foam in optimum condition base on previous chapter. The Results show that: pretreatment molasses can improve the yield of kojic, and H2SO4pretreatment advantageous to cell growth and kojic acid yield, the kojic acid concentration was5.738g/L, it’s the highest,2.7times of without pretreatment. Further study show that the molasses concentration has a greater impact on cell growth and kojic acid yield, when the total sugar concentration of molasses was80g/L, got the highest Kojic acid concentrations9.016g/L. |
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