Phosphate release and heavy metal accumulation by biofilm-immobilized and chemically-coupled cells of a citrobacter sp. pre-grown in continuous culture
✍ Scribed by John A. Finlay; Victoria J. M. Allan; Alex Conner; Maureen E. Callow; Gabriela Basnakova; Lynne E. Macaskie
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 225 KB
- Volume
- 63
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
A heavy metal-accumulating Citrobacter sp. was grown in carbon-limiting continuous culture in an air-lift fermentor containing raschig rings as support for biofilm development. Planktonic cells from the culture outflow were immobilized in parallel on raschig rings by chemical coupling (silanization), for quantitative comparison of phosphatase activity and uranyl uptake by both types of immobilized cell. The flow rate giving 50% conversion of substrate to product (phosphate) in flowthrough reactors was higher, by 35-40%, for the biofilmimmobilized cells, possibly exploiting a pH-buffering effect of inorganic phosphate species within the extracellular polymeric material. Upon incorporation of uranyl ions (0.2 mM UO 2
2+
), both types of cell removed more than 90% of the input UO 2 2+ at slow flow rates, but the chemically-coupled cells performed better at higher flow rates. The deposited material (HUO 2 PO 4 ) subsequently removed Ni 2+ from a second flow via intercalative ion exchange of Ni 2+ into the crystalline HUO 2 PO 4 .4H 2 O lattice. This occurred irrespective of the method of coupling of the biomass to the support and suggested that uranyl phosphate accumulated by both types of cell has potential as a bio-inorganic ion exchanger-a potential use for the uranium recoved from primary waste treatment processes.