Production of Rapamycin in Streptomyces hygroscopicus from Glycerol-Based Media Optimized by Systemic Methodology~S

摘要

Rapamycin, produced by the soil bacterium Streptomyces hygroscopicus, has the ability to suppress the immune system and is used as an antifungal, anti-inflammatory, antitumor, and immunosuppressive agent. In an attempt to increase the productivity of rapamycin, mutagenesis of wild-type Streptomyces hygroscopicus was performed using ultraviolet radiation, and the medium composition was optimized using glycerol (which is one of the cheapest starting substrates) by applying Plackett-Burman design and response surface methodology. Plackett-Burman design was used to analyze 14 medium constituents: M100 (maltodextrin), glycerol, soybean meal, soytone, yeast extract, (NH_4)_2SO_4, L-lysine, KH_2PO_4, K_2HPO_4, NaCl, FeSO_4.7H_2O, CaCO_3, 2-(N-morpholino) ethanesulfonic acid, and the initial pH level. Glycerol, soytone, yeast extract, and CaCO_3were analyzed to evaluate their effect on rapamycin production. The individual and interaction effects of the four selected variables were determined by Box-Behnken design, suggesting CaCO_3, soytone, and yeast extract have negative effects, but glycerol was a positive factor to determine rapamycin productivity. Medium optimization using statistical design resulted in a 45% (220.7 ± 5.7 mg/1) increase in rapamycin production for the Streptomyces hygroscopicus mutant, compared with the unoptimized production medium (151.9 ± 22.6 mg/1), and nearly 588% compared.with wild- type Streptomyces hygroscopicus (37.5 ± 2.8 mg/1). The change in pH showed that CaCO_3 is a critical and negative factor for rapamycin production.