Effects Of Different Substrates On The Important Metabolites Of Red Yeast Rice

Red yeast rice, as traditional fermented products of homology of medicine and food, has been widely used in China for centuries. Red yeast rice is a kind of fermented functional food, the acid form of lovastatin is an effective cholesterol-lowering component of red yeast rice, which is capable of reducing cholesterol by inhibiting the activity of HMG-CoA reductase enzyme, a rate-limiting enzyme of endogenous cholesterol synthesis. In this paper, Monacolin K (acid form) detection and quantification methods were established, the effects of different culture medium on the important metabolites in red yeast rice were studied, and the impact reasons was preliminary explored. The effects of fermentation conditions, drying and sterilization conditions on Monacolin K (acid form) in red yeast rice were also examined. The results provide a reference for the high quality of lipid-lowering Monascus products.The Monascus TUST001 fermentation products contain acid form Monacolin K ware determined by UPLC-MS, and the HPLC detection and quantification methods were established.0.1%phosphoric acid was added to the mobile phase, which can effectively detect the acid form Monacolin K. The lactone form can be completely converted to the acid form by adding of 0.1 mol/L NaOH (prepared with 50%of acetonitrile), and keeping at 50℃ for 1 hour and sonicating 1 hour.The contents of Monacolin K and GABA on different culture medium in Monascus fermented products were significantly different. Using unpolished rice as fermentation substrate, the content of acid form Monacolin K in KD-6 is highest,2.1 times of KD-4, content of lactone form Monacolin K in KD-2 is 1.6 times of that of KD-4, GABA content in KD-1 is 2.5 times of that of KD-6; with polished rice as fermentation substrate, acid form Monacolin K content in KD-5 is 2.9 times of that of KD4, the content of lactone form Monacolin K in KD-2 is 3.5 times of that of KD-4, the content of GABA in KD-5 is 3.1 times of that of KD-4. Monascus TUST001 metabolites do not contain citrinin, the ability to produce color value is low (the highest is 23.43u/g).The contents of protein, amylose and fatty acid in different fermentation matrix have no direct causal relationship with Monacolin K and GABA yield.The fermentation duration of 4 weeks and treatment with convective drying (after 110 "C sterilization) can improve the content of Monacolin K (acid form). In order to obtain higher quality lipid-lowering red yeast rice products, this experiment used acid form Monacolin K ratio as index to determine the best treatment conditions of the Monascus TUST001 fermentation products:The optimum sterilization time is 15min, after sterilization, the optimum drying temperature is 50℃, the optimum drying time is 2h. Monacolin K (acid form) content in our red yeast rice is higher than that of three commercially available lipid-lowering red yeast rice drugs S-1, S-2, S-3, which is 3.14 mg/g, the ratio of the acid form Monacolin K are 3.37,3.62 and 6.77 times that of S-1, S-2 and S-3, respectively.