Influence of culture age on exopolymeric substances from common laboratory bacterial strains: a study on yield, profile and Cu(II) biosorption

Extracellular polymeric substances (EPS) produced by laboratory strains Bacillus cereus and Pseudomonas aeruginosa were extracted from cultures incubated at various incubation periods (24, 48, 72, 96 and 120 h). At each sampling time, the EPS were analysed for yield, quality, functional groups present, and their efficacies in copper (Cu(II)) biosorption (using 30 and 50 ppm EPS). Results revealed that EPS yield was influenced by incubation period, with 48-h culture of B. cereus and 96-h culture of P. aeruginosa producing the highest yield of EPS at 8.30 mg and 6.95 mg, respectively. The EPS produced at various incubation periods have similar characteristics in solubility, quality and major functional groups (C-O, CH3, C=C, O-H) present. Efficacy of Cu(II) biosorption was influenced by the amount of EPS used and the EPS-metal incubation time. Although Cu(II) removal was higher for EPS from 24-h B. cereus (18.96%) and 48-h P. aeruginosa (19.19%) when 30 ppm was used, application of 50 ppm EPS demonstrated no distinct differences in amount of Cu(II) removed. This suggested that higher biomass of EPS used and longer EPS-metal incubation period, superseded the efficacy of EPS from various incubation periods.