Comparative Analysis on Metal Removal Potential of Exopolymeric Substances with Live and Dead Cells of Bacteria

This study investigated and compared the metal removal efficacy of exopolymeric substances (EPS), live and dead cells of Bacillus cereus, Staphylococcus aureus, Stenotrophomonas maltophilia and Pseudomonas fluorescens. Results revealed that dead cells of Gram-positive bacteria (B. cereus, S. aureus) showed better metal removal potential compared to live cells, while the contrary was observed for Gram-negative bacteria (S. maltophilia, P. fluorescens). The EPS from all bacterial isolates demonstrated the least efficacy in metal removal potential (9-30%) compared to live (12-63%) and dead (16-70%) cells. Comparing among bacterial isolates, the EPS of B. cereus was the most effective in biosorbing all metals (Cu: 27.94%, Pb: 34.29%, Zn: 23.15%, Cd: 14.65%, Cr: 26.15%). These were, however, lower than the amount of metals removed by live (Cu: 44.82%, Pb: 53.64%, Zn: 39.13%, Cd: 19.85%, Cr: 38.75%) and dead (Cu: 63.26%, Pb: 70.16%, Zn: 58.86%, Cd: 57.68%, Cr: 56.48%) cells of B. cereus. Fourier-transform infrared spectroscopy (FTIR) analysis suggests that the hydroxyl groups in EPS were primarily involved in metal biosorption. Mean metal removal in multi-metal systems (31.75 +/- 13.21%) were significantly inferior compared to single-metal systems (36.21 +/- 13.24%). This study revealed that EPS has the potential for metal removal although the amount of metal removed is lower than levels removed by live and dead cells. EPS remains an interesting alternative as the use of this non-toxic biomolecule is safer compared to live and dead cells. EPS can be further improved upon via cultivation methods or pre-treatment, to establish their feasible use for wastewater treatment.

Automated summary

This study investigated and compared the metal removal efficacy of exopolymeric substances (EPS), live and dead cells of different bacteria. It was found that dead cells of Gram-positive bacteria showed better metal removal potential compared to live cells, while the opposite was observed for Gram-negative bacteria. Among the bacterial isolates, the EPS of B. cereus demonstrated the most effective biosorption of metals. EPS has the potential for metal removal, although the amount of metal removed is lower than levels removed by live and dead cells. Multi-metal systems showed lower metal removal compared to single-metal systems.