Optimization of fermentation conditions for enhancing extracellular production of L-asparaginase, an anti-leukemic agent, by newly isolated Streptomyces brollosae NEAE-115 using solid state fermentation

Optimization of the fermentation conditions for extracellular production of L-asparaginase by Streptomyces brollosae NEAE-115 under solid state fermentation was investigated. The Plackett–Burman experimental design was used to screen 16 independent variables (incubation time, moisture content, inoculum size, temperature, pH, soybean meal + wheat bran, dextrose, fructose, L-asparagine, yeast extract, KNO3, K2HPO4, MgSO4.7H2O, NaCl, FeSO4. 7H2O, CaCl2) and three dummy variables. The most significant independent variables found to affect enzyme production, namely soybean + wheat bran (X6), L-asparagine (X9) and K2HPO4 (X12), were further optimized by the central composite design. We found that L-asparaginase production by S. brollosae NEAE-115 was 47.66, 129.92 and 145.57 units per gram dry substrate (U/gds) after an initial survey using “soybean meal + wheat bran” as a substrate for L-asparaginase production (step 1), statistical optimization by Plackett–Burman design (step 2) and further optimization by the central composite design (step 3), respectively, with a fold of increase of 3.05.