Abstract
The removal of sodium (Na) from seawater using two photosynthetic bacteria was investigated using Rhodobacter sphaeroides SSI (SSI) and Rhodovulum sp. which is a marine photosynthetic bacterium. Both Rhodovulum sp. and acclimated SSI were shown to grow well in a 3% NaCl supplemented glutamate-malate medium. The maximum rate of Na removal was 39.3% by SSI and 64.9% by Rhodovulum sp. after two days cultivation under static light conditions. However, Na was re-released back into the medium after two to three days. When a nutrient-supplemented seawater medium (3.3% NaCl, 13.10 gNa/l) was used, the maximum Na removal rates were 30.3% (9.05 gNa/l) by SSI and 48.9% (6.69 gNa/l) by Rhodovulum sp., under static light conditions. Similar growth and Na removal rates were found under aerobic dark cultivation. In this case, no re-release of Na was observed with either bacterium. Two stages culturing was conducted first, with Rhodovulum sp. and then with SSI replacement. The Na concentration was reduced to 0.79 gNa/l (94.0% removal) after cultivation for eight days under aerobic darkconditions. The supernatant was applied successfully as a liquid fertilizer in the cultivation of Japanese radish.
Highlights
Photosynthetic bacteria that produce extracellular polymeric substances (EPS) on the cell surface adsorb cationic metals such as Cd, Pb, Cr, Hg, Cu and As at rates between 85% and 100% using the negative charge of the EPS [1] [2]
This study focused on the Na removal using two photosynthetic bacterial strains using a synthetic medium and a nutrient supplemented seawater medium (NSSW medium)
It is well known that the energy status of the cells of photosynthetic bacteria affects the uptake of Na
Summary
Photosynthetic bacteria that produce extracellular polymeric substances (EPS) on the cell surface adsorb cationic metals such as Cd, Pb, Cr, Hg, Cu and As at rates between 85% and 100% using the negative charge of the EPS [1] [2]. SSI has been observed to adsorb Cs from waste water at rates approaching about 100% [3], but this seems to be closely related to the potassium transport system of photosynthetic bacteria [4]. Accumulate abundant EPS on its cell surface allowing it to perform relatively strong self-immobilization [5]
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