Statistical and equilibrium studies on enhancing biosorption capacity of Saccharomyces cerevisiae through acid treatment

In the present work dye sorption of methylene blue (MB) onto two different bakers' yeast (Saccharomyces cerevisiae) samples, untreated autoclaved yeast (UTY) and acid treated autoclaved yeast (ATY), was investigated. In order to study the effect of process variables and to optimize the acid treatment conditions central composite design was employed. A quadratic model was used to relate treatment efficiency to the treatment conditions, acid concentration and soaking time. The results were analyzed using statistical tools like F-test, Student's t-test and ANOVA to assess statistical significance of these factors. It was found that optimum acid concentration and soaking time were 2.1 N and 48 h respectively. After optimization equilibrium studies were carried out with both UTY and ATY prepared under optimum conditions. Using Langmuir and Freundlich isotherm models the equilibrium data were analyzed and it was confirmed that adsorption of MB onto UTY and ATY are feasible. It was found that MB uptake capacity of ATY was significantly higher than that of UTY (117.4 against 45.7 mg MB/g). FTIR analyses of the samples, before and after acid treatment, suggest that increase in MB adsorption was due to hydrolysis of yeast.