Improvement of tacrolimus production in Streptomyces tsukubaensis by mutagenesis and optimization of fermentation medium using Plackett-Burman design combined with response surface methodology.

Abstract

This study was conducted to enhance the production of tacrolimus in Streptomyces tsukubaensis by strain mutagenesis and optimization of the fermentation medium. A high tacrolimus producing strain S. tsukubaensis FIM-16-06 was obtained by ultraviolet mutagenesis coupled with atmospheric and room temperature plasma mutagenesis.Then, nine variables were screened using Plackett-Burman experimental design, in which soluble starch, peptone and Tween 80 showed significantly affected tacrolimus production. Further studies were carried out employing central composite design to elucidate the mutual interaction between the variables and to work out optimal fermentation medium composition for tacrolimus production. The optimum fermentation medium was found to contain 61.61g/L of soluble starch, 20.61g/L of peptone and 30.79g/L of Tween 80. In the optimized medium, the production of tacrolimus reached 1293mg/L in shake-flask culture, and reached 1522mg/L while the scaled-up fermentation was conducted in a 1000 L fermenter, which was about 3.7 times higher than that in the original medium. Combining compound mutation with rational medium optimization is an effective approach for improving tacrolimus production, and the optimized fermentation medium could be efficiently used for industrial production.