Biosorption of methylene blue from aqueous solution using free and polysulfone-immobilized Corynebacterium glutamicum: batch and column studies.

The amino acid fermentation industry waste, Corynebacterium glutamicum, has been found to possess excellent biosorption capacity towards methylene blue (MB). Due to practical difficulties in solid-liquid separation and biomass regeneration, C. glutamicum was immobilized in a polysulfone matrix. The pH edge experiments revealed that neutral or alkaline pH values favored MB biosorption. Isotherm experiments indicated that C. glutamicum, when in immobilized state, exhibited slightly inferior dye uptake compared to free biomass. Also considering the two forms, immobilized biomass took a long time to attain equilibrium. An attempt to identify the diffusion limitations in immobilized beads was successful, with the Weber-Morris model clearly indicating intraparticle as the rate controlling step. Regeneration of the free biomass was not possible as it tended to become damaged under strong acidic conditions. On the other hand, immobilized biomass performed well with 99% desorption of MB from the biosorbent with the aid of 0.1 mol/l HCl. The immobilized biomass was also successfully regenerated and reused for three cycles without significant loss in sorption capacity. An up-flow packed column loaded with immobilized biomass was employed for the removal of MB. The column performed well in the biosorption of MB, exhibiting a delayed and favorable breakthrough curve with MB uptake and % removal of 124 mg/g biomass and 70.1%, respectively.