To construct a first-order model that can predict the pigment production (dependent variable) as a function of the carbon source, peptone and MSG concentrations (independent variables), the analysis of variance (ANOVA) was used to evaluate the adequacy of fit. The regression coefficients for the pigment production by M. purpureus in submerged cultures are shown in Table 3. The larger the magnitude of the t-value and smaller the P-value, more significant is the corresponding coefficient (Myers & Montgomery, 2002). On the basis of the ANOVA, Eq. (1) was established, describing the pigment production as a function of independent variables: