Variations in the Bioaccumulation Rates of Heavy Metal by Immobilized and Free Gram-negative and Gram-positive Bacterial Cells Isolated From an aerated lagoon

Document Type : Original Article

Authors

1 Botany Department, Faculty of Science, Suez Canal University, Ismailia, Egypt

2 Botany Department, Faculty of Science, Suez Canal University, Suez, Egypt

Abstract

The uptake of heavy metals by all immobilized microbial cell strains (bacterial beads: bacterial cells in alginate) is better than by free cells. The average removal percentage for all six metals by Gram-positive bacterial beads showed that Bacillus megaterium (81%), Bacillus flexus (73%), Bacillus amyloliquefaciens (70%) and Bacillus cereus (66%). While Immobilized Gram-negative cells of Pseudomonas veronii and Rahnella aquatilis were good for the uptake of metals such as copper, nickel and cobalt. Rahnella aquatilis and Pseudomonas veronii accumulated Cu, Ni and Co by respectively (91.5%, 77 %), (90.1%, 85 %) and (75%, 74%), while Pb was only accumulated by Pseudomonas veronii (67 %). On the other hand, Sphingobacterium daejeonense and Roseomona saquatica were relatively weak in accumulating heavy metals. On the other hand, the uptake of heavy metals by all free microbial cell strains possessed no significant difference by varying metals type and bacterial strains, except Co and Pb were poorly accumulated. Immobilization in alginate beads provides a protective environment for these agents for sufficient time of heavy metals removal. Immobilized systems currently offer various advantages over free systems. Rahnella aquatilis was reported for the first time in this research as a potential organism for the bioaccumulation of some toxic heavy metals from domestic wastewaters.

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