Abstract:
The role of a metabolically independent lead removal mechanism in an industrially obtained lead-precipitating
consortium was investigated. Cultures were prepared under anaerobic conditions for 24 hours in batch
reactors starting with 20 g L-1 tryptone, 10 g L-1 yeast extract, 1.0 g L-1 NaCl and 0.43 g L-1 NaNO3. Bacteria
were suspended in 50 mM of sodium azide (NaN3) solution for 3 h to successfully inhibit the microbial
respiratory chain, thereby preventing bacteria growth and activity. Fourier-transform infrared spectroscopy
(FTIR) was used to inspect whether NaN3 deformed the structure of bacteria cell walls and changed material
characteristics.
Reactors containing 100 mL of 80 mg L-1 Pb(II) and 1.0 g/L NaCl were spiked with 1 mL of NaN3-sterilized
bacteria culture and sampled over a 3 h period. Bulk Pb(II) concentration and metabolic activity were
measured.
Results showed that NaN3 was an effective means to cease metabolic activity of the consortium without
altering the surface properties. Pb(II) is still removed from solution (61.7 %) by dead bacteria after NaN3
sterilization, indicating that the initial removal of Pb(II) from solution by the lead-precipitating consortium is an
abiotic process. FTIR analysis revealed functional groups such as carboxyl, amine, and phosphate playing a
role in Pb(II) biosorption.
Conclusions drawn from this study allow for future experimentation, modelling, and optimization of the
biosorption mechanism in an industrially obtained lead-precipitating consortium.
