Effect of liquid culture requirements on antifungal antibiotic production by Streptomyces rimosus MY02.

Streptomyces rimosus MY02 was isolated from a soil sample which was collected from the northeast of China. The effect of medium components (i.e. carbon and nitrogen sources) and other culture requirements (i.e. initial pH and temperature) on production of antifungal antibiotics by S. rimosus MY02 was investigated in our work. The best conditions for the strain MY02 in 250-ml Erlenmeyer flask, for example, initial pH, temperature, medium capacity, agitation rate, seed age, inoculum size and growth period, were 6.0, 28 degrees C, 50 ml, 180 rpm, 4 days, 10% (v/v) and 120 h, respectively. Components and dosage of the medium, which effect antibiotic production, were determined by uniform design combined with regression analysis; meanwhile, a regression model was established. The components and dosage of the best medium were starch, 53.313 g; defatted peanut powder, 9.376 g; (NH(4))(2)SO(4), 6.244 g; and NaCl, 5.836 g; in 1l of distilled water. Residual values obtained between the observed values by experiments and predicted values by the model are very low, and this result showed that the experimental results were well in consistence with the calculation results via the model. The antifungal antibiotic production by S. rimosus MY02 was improved by optimization of the components and culture requirements. The diameter of inhibition zone of the culture supernatant from S. rimosus MY02 against Fusarium oxysporium f sp. cucumarinum was 33.19 mm.