Research On Three Kinds Of Polyketides Of A Monascus

Monascus has been used for one thousand years in our country. During metabolism, monascus can synthetize not only primary metabolites, such as enzyme and organic acid, but also some bioactive secondary metabolites. Monascus pigments,lovastatin and citrinin are three kinds of polyketides. Monascus pigments are used as staining and antiseptic, and lovastatin can reduce cholesterol level in blood, however citrinin is nephrotoxic to human. So how to promote the production of pigments and lovastatin, while reducing citrinin level , is the foucus of monascus fermentation. The objective of this experiment is to research the production pattern and relationship of monascus pigments,lovastatin and citrinin of monascus AS3.531 under different conditions, in order to promote the production of pigments and lovastatin, while reducing citrinin level. The research is composed by five parts.In the first part, the detect method of lovastatin by double wave length UV spectrophotometry was established. The result showed that dilution level had significant effection to lovastatin recovery rate. When the dilution level was sufficient, the effection of pigment to lovastatin detection was reduced.1mL extraction was used to decolorate by Al₂O₃, and eluted by 75% ethanol. The 3-8mL eluent was used to detect lovastatin content under 246nm and 254nm. The average recovery rate of lovastatin is 98.8%, and coefficient of variation is 1.62%.In the second part, a detection method of citrinin was established by HPLC. Under the condition of SHIMADZU Shim-pack VP-ODS C18 column,fluorescent light waveλex=331nm andλem=500nm, column temperature 28℃,acetonitrile:methanol:H₂O=70:10:20, flow rate 1mL/min, sample size 20μL,citrinin has good linearity between 0.05-5mg/L, and the average retention time is 18.482min.The lowest detection limit is 5μg/L, and the average recovery rate is 98.17%, RSD=1.8%.In the third part, the cultivation conditions of lovastatin production by solid fermentation were optimized. Orthogonal experiment result showed that the optimize conditions were 28℃,Ph5.0,water content 60%,under this conditions,the production of lovastatin was 9.033×10^-6g/gIn the fourth part, the cultivation conditions and medium composition of pigment and citrinin liquid fermentation were optimized.The result of single factor experiment showed that the pigment and citrinin had the same production trend. But the result of response surface design is different from single factor experiment. By means of response surface design, the optimized conditions are 32℃,pH5.7 and rotate rate 150rpm. Under these conditions, the pigment value is 65.59U/mL, and citrinin is 14.54μg/mL. The composition and ratio of medium has important effect on pigment and citrinin production. Glycerol and peptone are good for pigment, and sucrose and (NH₄)₂SO₄ are good for citrinin. According to orthogonal experiment, the best ratio of carbon source to nitrogen source is glycerol3%, peptone1%, NaNO₃1%. Under these conditions, the pigment value is 95.94U/mL, without citrinin.In the fifth part,the solid fermentation conditions of pigment and citrinin were optimized. The results of orthogonal experiment showed that water content of solid medium is the most imoortant factor to affect pigment production, but for the citrinin it's pH. When the medium contents more than 50%water, the yellow pigmen will be more than red pigment. Under the following conditions: rice 60g, 37℃, pH5.5, water content 60%, the yield of pigment is 297.0U/g, and citrinin is 0.1465μg/g. When the conditions are as following: rice 40g, 32℃, pH5.0,water content 60%,the yield of citrinin is 0.0377μg/g, and pigment is 135.8U/g.