Statistical optimization of medium components to improve the chitinase activity of Streptomyces sp. Da11 associated with the South China Sea sponge Craniella australiensis

Abstract

In this paper, statistical Plackett–Burman design and Box–Behnken Response Surface Methodology were applied to optimize the medium components to improve the chitinase activity of Streptomyces sp. DA11 associated with South China Sea sponge Craniella australiensis. Firstly, galactose and peptone were found to be the suitable carbon and nitrogen sources for the growth and chitinase activity by single factor Seriatim–Factorial test. Secondly, galactose, colloidal chitin and MgSO 4·7H 2O were proved to have remarkable effects on chitinase activity. Finally, an optimal medium was obtained by Box–Behnken methodology, which consisted of 5.00 g/L galactose, 2.62 g/L colloidal chitin, 0.10 g/L MgSO 4·7H 2O and 12.5 g/L peptone, 1.5 g/L PO 4 3− (KH 2PO 4 0.45 g/L, K 2HPO 4 1.05 g/L), 12.5 g/L powder chitin, 0.03 g/L FeSO 4 and 0.03 g/L ZnSO 4·7H 2O with artificial sea water (ASW). With this optimal medium, both the chitinase activity and cell growth were remarkably enhanced. The chitinase activity of 1559.2 U/g cell dry weight (36.43 U/mL) and the maximum cell dry weight of 23.3 g/L were reached after incubation of 72 h, which were 39.2-fold and 2.6-fold higher than that of the basic medium, respectively. The results suggest that Streptomyces sp. DA11 isolated from marine sponge might be a potential strain for the production of chitinolytic enzymes. To our knowledge, this is the first report of the statistical optimization of chitinase production from marine sponge-associated Streptomyces.