Primary Study On Biosynthesis Mechanism Of Monascus Pigment And Mix-culture Of Monascus

The biosynthesis mechanism of monascus pigment and effect of mix-culture on pigment biosynthesis were studied in this dissertation.First, feeding experiment and resting cell system were used to confirm precursors of pigments. The effects of different amino acids and branched fatty acids on pigments production were investigated, and the results showed those amino acids and branched fatty acids, such glycine ( 5mmol·L-1 ),valine(2mmol·L-1),isoleucine(2mmol·L-1),methionine(1mmol·L-1),glutamine(2mmol·L-1),arginin(e1mmol·L-1),acetat(e2mmol·L-1),propionat(e3mmol·L-1)could act as precursors and mostly stimulate pigments biosynthesis. Besides, all of these compounds could be transformed to the precursors of polyketide biosynthesis. So the ployketide pathway was presumed to be the main biosynthetic pathway of monascus pigments.In order to testify the hypothesis above, influences of different metabolic pathways' inhibitors on monascus pigment biosynthesis were examined and the following results were obtained. Inhibitor of shikimic acid pathways -trimethylamine or inhibitors of mevalonic acid pathways-anthranilic acid and 3,4-dihydroxybenzoic acid had no effects on pigment biosynthesis. Whereas, pigment biosynthesis was severely inhibited by inhibitors of the key enzymes in the polyketide pathways, such as the specific inhibitors ofβ-ketoacyl-acylcarrier protein synthase-iodiacetamide or imidazole, the thioesterase inhibitor- 2,4-dinitrofluorobenzene, methyl-malonylCoA isomerase Cu2+, Zn2+. Besides,pigment biosynthesis was totally inhibited when added 1mmol·L-1 iodiacetamide, 1mmol·L-1 imidazole, 2mmol·L-1 2,4-dinitrofluorobenzene, 4mmol·L-1 Cu2+, 10mmol·L-1Zn2+. Polyketide pathway was therefore confirmed as the main biosynthetic pathways of monascus pigment. It had no effects on pigment biosynthesis when added 200mg·L-1 sulphanilamide .Because the growth of lactic acid bacteria and saccharomyces were faster than monascus, they quickly consumed lots of nutrient substance. Mixed culture is adverse to monascus growth and pigment excretion. But the metabolic products of them are good for pigment excretion.