Study On Production Of Monascus Yellow Pigments In Submerged Fermentation

As a kind of traditional natural pigment, Monascus pigments have been widely used in the field of food coloring. The fermentation of Monascus pigment is considered to be one of the most successful examples in the field of microbial fermentation for natural colorant. Monascus can product pigments with different color tune. Among of them, amplification of red pigments fermentation has been realized in the industry while yellow and orange Monascus pigments is still been explored in laboratory. At present, the main problem in yellow pigment production by submerged fermentation of Monascus is low yield. To improve the output of Monascus yellow pigments(MYP), the technological conditions of fermentation was optimized by referencing the synthetic pathway of the pigments.On the basis of the previous study, Monascus sp. sjs-6 was screened as the MYP production strain from amounts of Monascus strains. This because the pigments produced by Monascus sp. sjs-6 with a single peak at 420 nm which was in the region of MYP’ absorption wavelength. Then, fermentation conditions were studied by single factor experiment and orthogonal experiment. The optimal fermented conditions were as follows: 60 g/L corn starch, 4 g/L(NH4)2SO4 in the culture medium, initial p H 5.0, at 30℃ for 6 days. The yield of MYP reached to 378.0 U/m L.In order to further improve the yellow pigment production, carbon feeding was applied in shaking flask. Firstly, the influences of various carbon sources(glucose, fructose, maltose, Sugar, corn starch and dextrin) feeding on the fermentation of Monascus sp. sjs-6 were determined. Feeding glucose with 1 g in 50 m L at 72 h, 96 h could greatly stimulate the pigments production and cell growth. The content of yellow pigments could reach to 624.7 U/m L under these conditions, which was 72.4% higher than that without feeding carbon.During the experiment, it was found that 4 g/L(NH4)2SO4 was not suitable for MYP production in 5 L stirred bioreactors. So we adjusted the concentration of(NH4)2SO4 to a proper level to control the biomass and improve the content of pigments. In addition, effects brought by ventilation and rotate speed were also investigated in this study. Results showed that dissolve oxygen(DO) of fermentation broth should be remain above 10% with the stirring rate less than 550 r/min in 10 L stirred bioreactor. Then, a comprehensive regulation by taking the advantages o f the integrated strategy of nitrogen source regulation and DO control as conducted in 50 L stirred bioreactor. Under this condition, MYP yield reached to 397.2 U/m L.To obtain the relatively pure MYP the extraction solvents and the thin layer chromatography(TLC) isolation conditions were also investigated. It was found that extracting by absolute ethyl alcohol at 40℃ for 30 min was the most effective. Using the mixture of methyl-benzene: ethyl acetate: methanoic acid(7: 3: 1, v/v/v) as solvent for MYP isolation by TLC, 6 bands could be displayed on the chromatoplate under the UV lamp at 365 nm. Meanwhile, two yellow bands with Rf value of 0.869 and 0.817 were obtained. No orange or red Monascus pigments presented on chromotoplates, which proved that high degree of MYP can be produced by this fermentation process.