Study On Lovastatin Fermentation By Monascus Species

Lovastatin, a secondary metabolite of some Monascus, is a potent competitiveinhibitor of3-hydroxy-3-methylglutaryl-coenzyme A （HMG-CoA） reductase, thereby it haseffective functions to decrease blood sugar and blood fat. Monascus H8, the strain with thehighest yield of Lovastatin, was screened from several strains.HPLC-MS, a method for structure identification of Lovastatin in the culture ofMonascus H8, was adopted in this thesis and the result showed that the whole Lovastatin inthe culture of Monascus H8was Lovastatin hydroxy acid. The standard substance ofLovastatin lactone was hydrolyzed to Lovastatin hydroxy acid by means of alkalinehydrolysis, with the conversion ratio of91.6%.Shaking-flask fermentation kinetics model of Monascus H8as the test strain wasconstructed. Logistic equation was proposed for growth, Luedeking-Piret equation forLovastatin biosynthesis and Luedeking-Piret-like equation for substrate consumption. Thekinetic model provided a reasonable description for variations of biomass, product andsubstrate consumption along with the fermentation process.The best fermentation condition was obtained based on the single factor test and themultivariate orthogonal polynomial regression model. It showed the optimum mediumcompositions were: glycerol （60mL/L）, NaNO₃（3g/L）, soybean powder （3g/L）, K₂HPO₄（1g/L）, MgSO₄·7H₂O （0.5g/L）, KCl （0.5g/L）, FeSO₄·7H₂O （0.01g/L） and pH5.0. Theoptimum technological parameters were as follows: culture temperature,28.43℃;inoculation size,10.10%; dissolved oxygen,96.7%; fermentation time,15d. Under theseculturing conditions, Lovastatin productivity of liquid fermentation was142.51mg/L.Biosynthesis of Monascus pigment was closely related to biosynthesis of Lovastatin. Itwas indicated that the productivity of Monascus pigment from Monascus H8wereimproved with the increase of temperature and inoculation to some extent. But the yield ofLovastatin was a sharply fall.Take yeast cell as an example, the promoting effect of foreign elicitor to Lovastatinproductivity in Monascus H8was researched in this paper. Results showed that, When1.5mL wall-broken solution of yeast cells （cultured for2days） was added to the culture of Monascus H8, the yield of Lovastatin reached to334.01mg/L, which was increased by1.35times compared with the control culturing. The fermentation time was shortened from15d to13d. It could help to save the cost for the fermentation.