Chemical modification of Corynebacterium glutamicum to improve methylene blue biosorption

This research examines the possibility of enhancing the biosorption potential of a fermentation industry waste (Corynebacterium glutamicum) towards methylene blue (MB). The biosorption capacity was enhanced via succination, which chemically modified the amine groups to carboxyl. Experiments at different pH conditions demonstrated that both raw and succinated C. glutamicum performed well in MB biosorption at neutral or basic conditions. Biosorption isotherm experiments revealed that the succinated biomass outperformed raw biomass in MB biosorption but underperformed compared to two commercial activated carbons (SPC-100 and SPS-200). The MB sorption capacities were 207.3, 337.5, 457.4 and 500.6 mg/g for raw biomass, succinated biomass, SPC-100 and SPS-200, respectively. Kinetic experiments revealed that almost complete biosorption equilibrium was attained within 5 min, followed by complete saturation in 30 min, for both forms of C. glutamicum. Desorption experiments were optimized at a solution pH of 2, to attain an approximate elution efficiency of 99.7% for MB-loaded C. glutamicum. Conversely, desorption was difficult with MB-loaded activated carbons, with elution efficiencies of only 5-6.1% being achieved. Regeneration experiments were only possible with succinated C. glutamicum, which performed well in five repeated cycles with high MB-removal efficiencies.