Salt-stimulation of caesium accumulation in the euryhaline green microalga Chlorella salina: Potential relevance to the development of a biological Cs-removal process

S. V. Avery, G. A. Codd, G. M. Gadd (Lead / Corresponding author)

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    22 Citations (Scopus)

    Abstract

    Accumulation of Cs+ by Chlorella salina was 28-fold greater in cells incubated in the presence than in the absence of 0.5 M-NaCl. An approximate 70% removal of external Cs+ resulted after 15 h incubation of cells with 50 μM-CsCl and 0.5 M-NaCl. LiCl also had a stimulatory effect on Cs+ uptake, although mannitol did not. Cs+ influx increased with increasing external NaCl concentration and was maximal between 25-500 mM-NaCl at approximately 4 nmol Cs+ h-1 (106 cells)-1. Little effect on Cs+ uptake resulted from the presence of Mg2+ or Ca2+ or from varying the external pH, and Cs+ was relatively non-toxic towards C. salina. At increasing cell densities (from 4 x 105 to 1 x 107 cells ml-1), decreasing amounts of Cs+ were accumulated per cell although the rate of Cs+ removal from the external medium was still greatest at the higher cell densities examined. Freely suspended C. salina and cell-loaded alginate microbeads accumulated similar levels of Cs+, however, 46% of total Cs+ uptake was attributable to the calcium-alginate matrix in the latter case. When Cs+-loaded cells were subjected to hypoosmotic shock, loss of cellular Cs+ occurred allowing easy Cs+ recovery. This loss exceeded 90% of cellular Cs+ when cells were washed with solutions containing ≤ 50 mM-NaCl between consecutive Cs+ uptake periods; these cells subsequently lost their ability to accumulate large amounts of Cs+. Maximal Cs+ uptake (approximately 85.1% removal after three 15 h incubations) occurred when cells were washed with a solution containing 500 mMNaCl and 200 mM-KCl between incubations. The relevance of these results to the possible use of C. salina in a salt-dependent biological Cs-removal process is discussed.

    Original languageEnglish
    Pages (from-to)2239-2244
    Number of pages6
    JournalJournal of General Microbiology
    Volume139
    Issue number9
    DOIs
    Publication statusPublished - 1 Sept 1993

    ASJC Scopus subject areas

    • Microbiology

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