An extremely radioresistant green eukaryote for radionuclide bio-decontamination in the nuclear industry

Abstract

International audienceNuclear activities generate radioactive elements which require processes for their decontamination. Although biological remediation has proved efficient in industrial applications, no biotechnology solution is currently operational for highly radioactive media. Such a solution requires organisms that accumulate radionuclides while withstanding radioactivity. This paper describes the potentialities of an extremophile autotrophic eukaryote, Coccomyxa actinabiotis nov. sp., that we isolated from a nuclear facility and which withstands huge ionizing radiation doses, up to 20,000 Gy. Half the population survives 10,000 Gy, which is comparable to the hyper-radioresistant wellknown prokaryote Deinococcus radiodurans. Cell metabolic profile investigated by nuclear magnetic resonance was hardly affected by radiation doses of up to 10,000 Gy. Cellular functioning completely recovered within a few days. This outstanding microalga also strongly accumulates radionuclides, including 238U, 137Cs, 110mAg, 60Co, 54Mn, 65Zn, and 14C (decontamination above 85% in 24 h, concentration factor, 1,000-450,000 mL g-1 fresh weight). In 1 h, the microalga revealed as effective as the conventional physico-chemical ion-exchangers to purify nuclear effluents. Using this organism, an efficient real-scale radionuclide bio-decontamination process was performed in a nuclear fuel storage pool with an important reduction of waste volume compared to the usual physico-chemical process. The feasibility of new decontamination solutions for the nuclear industry and for environmental clean-up operations is demonstrated

Extremophilic micro-algae and their potential contribution in biotechnology

“…An extreme form of metal tolerance is found in those organisms that can grow in the presence of radionuclides and which are therefore extremely resistant to ionizing radiation. For example Rivasseau et al (2013) have isolated Coccomyxa actinabiotis from a pool used to store spent fuel elements and this is reported to withstand gamma ray doses of radiation up to 20 KGy and to accumulate, and remove from solution, a range of nuclides including 110m Ag, 65 Zn and 137 Cs 60 Co, and 238 U. Earlier work has also shown cyanobacteria to possess a degree of radiation resistance (Kraus, 1969) The possibility therefore exists to use phycoremediation of dealing with radiation contamination in water.…”

“…Sometimes these organisms possess additional qualities such as the ability to cope with very high levels of gases such as CO 2 , or grow in the presence of high concentrations of metals and some can thrive in combinations of more than one stress (polyextremophiles). Some organisms even possess a remarkable ability to grow under very high ionizing radiation levels and to accumulate radionuclides (Rivasseau et al, 2013). It is our contention that some of these properties may be of use in biotechnological applications.…”

Fatty Acid Content and Profile of the Novel Strain of Coccomyxa elongata (Trebouxiophyceae, Chlorophyta) Cultivated at Reduced Nitrogen and Phosphorus Concentrations

“…Coccomyxa even occurred as a contaminant in the cooling water of a nuclear power plant (Rivasseau et al. ) and in chemical solutions and distilled water in laboratories (Braune ). This wide ecological plasticity is one of the predominant arguments to identify highly productive strains of algae, in order to use them in biotechnology (Maltsev et al.…”

“…Representatives of the genus can be found as free-living in terrestrial habitats, as soil algae and associated with mosses, as lichen photobionts, as well as planktonic in freshwater ecosystems. Coccomyxa even occurred as a contaminant in the cooling water of a nuclear power plant (Rivasseau et al 2013) and in chemical solutions and distilled water in laboratories (Braune 1964). This wide ecological plasticity is one of the predominant arguments to identify highly productive strains of algae, in order to use them in biotechnology (Maltsev et al 2017b).…”

Extremophile Microalgae: the potential for biotechnological application

“…Microorganisms of extreme environments can be distinguished as thermophiles (lovers of high temperature), psychrophiles or cryophiles (cold‐loving organisms), halophiles (high salt‐loving organisms), acidophiles (cells thriving at low pH), alkaliphiles (cells thriving at high pH), and radiation‐resistant phototrophs (Seckbach and Oren , Rivasseau et al. , Varshney et al. ).…”