UC Davis

The removal efficiency of Cu2+ by Spirulina platensis (strain FACHB-834), in viable and heat-inactivated forms, was investigated in the presence and absence of linear alkylbenzene sulfonate (LAS). When the initial Cu2+ concentration was in the range of 0.5-1.5 mg · L-1, a slight increase in growth rate of FACHB-834 was observed. In contrast, when Cu2+ or LAS concentrations were at or higher than 2.0 or 6.0 mg · L-1, respectively, the growth of FACHB-834 was inhibited and displayed yellowing and fragmentation of filaments. The presence of LAS improved Cu2+ removal by ~20%, and accelerated attainment of Cu2+ retention equilibrium. For the 2- mg · L-1 Cu2+ treatments, retention equilibrium occurred within 2 d and showed maximum Cu2+ removal of 1.83 mg · L-1. In the presence of LAS, the ratio of extracellular bound Cu2+ to intracellular Cu2+ taken up by the cells was lower (1.05-2.26) than corresponding ratios (2.46-7.85) in the absence of LAS. The percentages of extracellular bound Cu2+ to total Cu2+ removal (both bound and taken up by cells) in the presence of LAS ranged from 51.2% to 69.3%, which was lower than their corresponding percentages (71.1%-88.7%) in the absence of LAS. LAS promoted biologically active transport of the extracellular bound form of Cu2+ into the cell. In contrast, the addition of LAS did not increase the maximum removal efficiency of Cu2+ (61.4% ± 5.6%) by heat-inactivated cells compared to that of living cells (59.6% ± 6.0%). These results provide a theoretical foundation for designing bioremediation strategies using FACHB-834 for use in surface waters contaminated by both heavy metals and LAS.