Screening Of Antitumor Active Substances From Myxobacteria

Myxobacteria was a kind of advanced prokaryotes, which could produce richful active substances with structure diversity and strain speciality. And the ratio of bioactive strain was high, thus myxobacteria was one of the important source of antitumor natural compounds screening.With high through in vitro screening method, we examined activity against human colon cancer cells (HCT-15) of fermentation products, which were fermented by 158 myxobateria strains belonging to different species. The result indicated that the fermentation products from 48 myxobateria strains could act efficiently on cancer cells, and the inhibition rate was over 50%. The active screening rate lived up to 30%. Choosing 18 myxobateria strains whose inhibition rate reached to 65% processed the continuous selection and stability test. The result of continuous selection was the same as the preliminary selection, and the 18 myxobateria strains had excellent stability.We choosed strain 92006 and strain 92094 which have higher antitumor activity.The experiment measured their growth curve, the antitumor activity of fermentation products at different concentrations and the stability of fermentation products. The result showed that the optimum seed culture time and the optimum fermentation culture time were 112 hours and 168 hours respectively. The optimum pH value was between 7 and 8 during fermentation. The antitumor activity of strain 92006 and strain 92094 depended on the concentration. The active products from strain 92006 are stable to the acid, alkaline and heat, but the active products from strain 92094 are only stable to the alkaline and heat.By cultured with ten different fermentation mediums, we determined three of them, which were suitable for the growth of strain 92006 and strain 92094 by the wet weight of cells and the inhibition rate that fermentation product acted on cancer cells. Then we combined the three fermentation mediums with different seed mediums. The result indicated that CAS and G52 were the optimum seed medium for strain 92006 and strain 92094 respectively, and JA-H and 1B12 were the optimum fermentation medium for strain 92006 and strain 92094 respectively.Besides, through orthogonal test and variance analysis method, the optimum fermentation medium components of strain 92006 included Starch 1%, Degrease soymeal 0.1%, Yeast extract 0.3%, MgSO4·7H2O 0.15%, HEPES 1.15%, CaCl2 0.05%, Glucose 0.2%, and the optimum fermentation medium components of strain 92094 included Potato starch 2%, Tryptone 1%, Microelement liquid 0.5mL. Through optimizing components of fermentation medium, the result showed that at concentration of 10-2, the inhibition rate that fermentation product acted on cancer cells of strain 92006 and strain 92094 were 91% and 84% respectively.