RESUMO
To improve biomass production and glucoamylase activity (GA) by Candida famata, culture conditions were optimized. A 2(3) full factorial design (FFD) with a response surface model was used to evaluate the effects and interactions of pH (X1 ), time of cultivation (X2 ), and starch concentration (X3 ) on the biomass production and enzyme activity. A total of 16 experiments were conducted toward the construction of an empiric model and a first-order equation. It was found that all factors (X1 , X2 , and X3 ) and their interactions were significant at a certain confidence level (P < 0.05). Using this methodology, the optimum values of the three tested parameters were obtained as follows: pH 6; time of cultivation 24 H and starch concentration 7 g/L, respectively. Our results showed that the starch concentration (X3) has significantly influenced both dependent variables, biomass production and GA of C. famata. Under this optimized medium, the experimental biomass production and GA obtained were 1.8 ± 0.54 g/L and 0.078 ± 0.012 µmol/L/Min, about 1.5- and 1.8-fold, respectively, higher than those in basal medium. The (R(2) ) coefficients obtained were 0.997 and 0.990, indicating an adequate degree of reliability in the model. Approximately 99% of validity of the predicted value was achieved.
