Statistical optimization of medium components for κ-carrageenase production by Pseudomonas elongata

Pseudomonas elongata, a κ-carrageenase producing marine bacterium, was isolated from West coast of Gujarat, India and for the first time, its nutritional requirement for κ-carrageenase production was defined using statistical optimization method. The important medium components identified by Plackett–Burman design were κ-carrageenan, yeast extract, NaCl, K2HPO4 and KH2PO4. These variables were further used in central composite design where carrageenase production, pH and biomass were responses used in different models to evaluate individually fit ones. Quadratic model was found to be fit for carrageenase production and pH, however, for biomass, 2F1 model was found to be fit after performing power transformation. In multiresponse analysis, medium formulation consisting of (g l−1): κ-carrageenan 0.2, yeast extract 0.4, NaCl 10.8, K2HPO4 0.3 and KH2PO4 0.1, was found to predict κ-carrageenase production of 32.08 units mg−1 protein with overall highest desirability of 0.679 as compared to other formulations. The selection of model was done on basis of high adjusted R2 value and lowered p-value for each model in individual analysis of each response. Through desirability analysis, it was found that for carrageenase production by P. elongata, biomass played an important role as compared to pH. Through statistical optimization method, 32-fold increase in κ-carrageenase production was achieved as compared to medium reported in the literature. Furthermore, through response surface experimental design, medium consisting of (g l−1): κ-carrageenan 0.2, yeast extract 0.7, NaCl 22.2, K2HPO4 0.1 and KH2PO4 0.2, was found to produce an activity of 60.7 units mg−1 protein. However, this does not depict the interactions among all the components as well as their combined effect on the responses.