Investigation of bioaccumulation of metal complex dyes and chromium ions in textile wastewaters by Saccharomyces cerevisiae and Candida tropicalis yeasts

In this study, the bioaccumulation of Violet 90 metal-complex dye and chromium by growing cells of Saccharomyces cerevisiae ve Candida tropicalis yeasts were investigated in growth media containing sugarbeet bagasse as carbon and energy source. At the first part of the study, the effect of yeast adaptation on dye, initial pH, initial dye and reducing sugar concentration on bioaccumulation performance of dye S. cerevisiae and C. tropicalis yeasts were examined. The highest dye removal yields obtained with adapted S. cerevisiae and C. tropicalis cells at 10 g/L initial reducing sugar concentration and 50 mg/L initial dye concentration and at pH 5 were 74.4 % and 42.9 % respectively.Monod equation was used to describe the growth of S.cerevisiae and C.tropicalis in the absence of dye and chromium ions. The values of µm (specific growth rate) and KS (Monod saturation constant) for S. cerevisiae and C. tropicalis were determined as 0.473 saat-1, 3.16 g/L and 0.253 saat-1 , 0.765 g/L respectively from Monod equation by linear regreassion method. Linear mixed type inhibition model was tested to characterize the dye inhibition on growth of S. cerevisiae and C. tropicalis yeasts. The values of KI (Inhibition constant) were estimated as 1132 mg/L for S. cerevisiae and 546 mg/L for C. tropicalis.At the next part of study, the effect of initial pH on bioaccumulation of chromium (VI) by S. cerevisiae and C. tropicalis yeast was investigated. Chromium uptake percentage was seen to be maximum at pH 5 and obtained as 4.5 % with S.cerevisiae and 30 % C.tropicalis at this pH. The effect of initial reducing sugar and initial chromium concentration on bioaccumulation of chromium by C.tropicalis was also investigated. The inhibition effect of chromium (III) on the specific growth rate of yeast was expressed by linear mixed type inhibition model and KI (Inhibition constant) was determined as 96.6.The combined effect initial dye and chromium(III) concentration on binary bioaccumulation of dye and chromium (III) was investigated using Box-Wilson experimental design method in 10 g/L reducing sugar concentration. ANOVA analysis done by Design Expert 7.0 package programme demonstrated that both have statistically significant effect on dye and chromium removal.At the last part of this study, dye bioaccumulation by S.cerevisiae was investigated in the continuous reactor flow system. The effect of dilution rate of dye removal was investigated and optimum dilution rate for dye bioaccumulation was estimated as 0.104 saat-1(0.87 mL/dak.) with 30 % dye uptake percentage.