Metal resistance and removal by two strains of the green alga, Chlorella vulgaris Beijerinck, isolated from Laguna de Bay, Philippines

Abstract

Two strains of Chlorella vulgaris Beijerinck isolated from two different sites in Laguna de Bay, Philippines, were studied for their resistance and ability to remove four metal ions, i.e., Cu2+, Cr6+, Pb2+, and Cd2+ added separately in BG-11 growth medium. The growth of the two strains was severely inhibited at 2 mg.L-1 of Cu2+, 5 mg.L-1 of Cr6+, 8 mg.L-1 of Pb2+, and 10 mg.L-1 of Cd2+. However, the two strains exhibited different EC50 values for the same metal ion. The WB strain had a significantly higher resistance (p<0.01) for Cd2+ and Cr6+ compared with the SB strain, while the SB strain had significantly higher resistance (p<0.01) for Cu2+ compared with the WB strain. On the other hand, the two strains behaved differently in their capacity to remove the metal ions in BG-11 medium containing 1.0 mg.L -1 of the three metal ions, except for Cu2+, which was added at 0.1 mg.L-1. The WB strain showed the highest removal of Cd2+ at 70.3% of total, followed by Pb2+ at 32%, while the SB strain exhibited the highest removal of Pb2+ at 48.7% followed by Cd2+ at 40.7% of the total. Both strains showed the least removal of Cr6+ at 28% and 20.8% of the total for the WB and SB strains respectively. The percentage removal for Cu2+ was 50.7% and 60.8% for the WB and SB strains respectively. After 12 days of incubation, both strains showed that a greater percentage of the metal ions removed were accumulated intracellularly than adsorbed at a ratio of at least 2:1. Both strains manifested the same cytological deformities, like a loss of pyrenoids at 10 mg.L-1 in all four metal ions. Discoloration and disintegration of chloroplasts were observed at 1.0 mg.L-1 in Cu2+ and 5 mg.L-1 in Cr6+. The nonrelease of autospores from the mother cells was observed at 10 mg.L-1 in Cu2+ and Cr 6+. © 2007 Springer Science+Business Media B.V.

Source or Periodical Title

Journal of Applied Phycology

ISSN

9218971

Page

701-710

Document Type

Article

Subject

Chlorella vulgaris Beij., Laguna de Bay, Metal resistance, Removal

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