| Red yeast rice is a traditional Chinese medicine with both food and therapy in our country.Monascus polysaccharides produced by Monascus are mainly composed of glucose,galactose and mannose,and have biological activities such as enhancing immunity,anti-aging,and inhibiting tumors.In this experiment,a Monascus strain was isolated and screened from red yeast rice.After ITS sequence identification and analysis,the strain was Monascus purpureus,named Monascus purpureus Y1.The effects of liquid shaking culture and liquid shaking-standing two-stage culture on the polysaccharide production efficiency and gene expression of key enzymes in polysaccharide synthesis of Monascus purpureus Y1 were compared.It was found that the two-stage culture method was more favorable for the production of polysaccharides by Monascus purpureus Y1.Plackett-Burman test and response surface design were used to optimize the medium and culture conditions of the twostage method,which effectively improved the production of exopolysaccharides,and preliminarily explored the antioxidant activities of exopolysaccharides and mycelial polysaccharides in vitro.Monascus purpureus Y1 was cultured by liquid shaking culture and shakingstanding two-stage culture,respectively,and the effects of the two fermentation culture methods on cell growth and the production of mycelial polysaccharide and exopolysaccharide were compared.Under the shaking culture condition,the production of exopolysaccharide of Monascus purpureus reached the maximum value on the 12 th day,which was 1.282 g/L,and the mycelium polysaccharide production reached the maximum value of 0.122 g/L on the 15 th day;However,by shaking-static culture,the yields of exopolysaccharides and mycelial polysaccharides of Monascus purpureus reached 1.374 g/L and 0.198 g/L on the 9th day.Compared with shaking culture,polysaccharide produced by shaking-standing two-stage culture method had shorter fermentation period and higher efficiency.Fluorescence quantitative PCR was used to analyze the expression of key enzymes in the polysaccharide synthesis pathway of Monascus purpureus cultured in two ways.After analysis,the expression levels of PGM,UGP and AGS1 in shaking-static culture were 1.06,1.98 and 0.8 times higher than those in shaking culture.It can be seen that the two-stage culture method of shaking and standing is an effective method for the production of polysaccharides by fermentation of Monascus purpureus Y1.This method was used for the first time and the fermentation conditions were optimized.Taking Monascus purpureus exopolysaccharide production as the response value,the carbon source,carbon source content,nitrogen source and nitrogen source content of the medium,as well as the time,inoculum amount,liquid filling amount,temperature and shaking speed of the culture conditions were analyzed by single factor test,Plackett-Burman test and response surface test.The optimized conditions were as follows: the glucose content was 45 g/L,the peptone content was 9 g/L,the temperature was 35 °C,the liquid volume was 180 m L,the inoculum volume was10%,and the shaking speed was 180 r/min.When the Monascus purpureus Y1 was cultivated under the optimized conditions,the yield of exopolysaccharide was significantly increased,which was 1.374 g/L before optimization and 1.936 g/L after optimization,and the yield was increased by 1.41 times.Through single factor experiment and orthogonal experiment,the material-liquid ratio,extraction temperature,extraction time and ultrasonic time were optimized.After optimization,the optimal conditions for the extraction of Monascus purpureus mycelial polysaccharide were determined as the ratio of solid to liquid of 1:20,the extraction time of 4 h,the extraction temperature of 70 °C,and the ultrasonic time of10 min.Under these conditions,the mycelial polysaccharide of Monascus purpureus was extracted,and the total reducing power and scavenging ability of mycelial polysaccharide and exopolysaccharide were determined.The results showed that the exopolysaccharides and mycelial polysaccharides of Monascus purpureus had certain scavenging ability and strong reducing ability to DPPH free radicals,superoxide anion free radicals and hydroxyl free radicals,and the scavenging ability and reducing ability... |
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