Microalgal photosynthetic activity measurement system for rapid toxicity assessment

Abstract

A systematic biosensor is constructed for the estimation of toxic compounds based on photosynthetic activity measurement in Selenastrum capricornutum cells. The photosynthetic response was evaluated as a function of light intensity, cell concentration and initial dissolved oxygen. The inhibitory effect of some toxicants (1-butyl-3-methylimidazolium tetrafluoroborate, methanol) on dissolved oxygen production was also determined. In all cases, a toxic response was detected (i.e. a dose-related inhibition of photosynthetic activity was observed). For the present system, a time of only 2 h was needed to predict EC50 values as compared to 96 h for a conventional algal assay based on algal growth rate. Thus, the developed biosensor was proved to be useful as a rapid and simple test method in environmental toxicity assessment.

Toxicity assessment of common organic solvents using a biosensor based on algal photosynthetic activity measurement

“…Additionally, the log 10 EC 50 (/µM) values of methanol, dimethylformamide, and isopropanol estimated using the same alga for 96 h were 5.85, 4.37, and 5.29, respectively (Cho et al 2008a). The log 10 EC 50 value of 1-butyl-3-methylimidazolium tetrafluoroborate measured by the presented system was very similar to that by traditional algal toxicity test for 96 h (Cho et al 2008b). For the practical application of this system, it is necessary to improve its sensitivity by increasing the incubating time of algae with toxicants, using more sensitive photosynthetic organisms to specific toxicants, or using extracted enzymes that play important role in photosynthesis.…”

“…The reason why the initial oxygen level was decreased to 1-3 mg L −1 was to easily observe the change of oxygen concentration and to overcome potential problem of oxygen build-up inside of reaction vessel. However, our previous experiments (Cho et al 2008b) showed that initial oxygen concentration did not significantly affect the photosynthetic activity. The gas mixture used in this experiment contained 99% N 2 and 1% CO 2 so as to supply an extra carbon source for the algal photosynthesis.…”

“…Construction of the experimental device Figure 1 shows a schematic diagram of the toxicity estimation system, which is reproduced from our previous article (Cho et al 2008b). The reaction vessel (1) was a double-jacket cylinder made of Pyrex® glass, which can remove the scattering effect.…”

“…Consequently, there is a need to design a simple and effective biosensor to quickly estimate the toxicity of volatile organic solvents without the loss of toxicants due to their volatile property. As a development of the research work carried out by our group, we present here the results of toxicity tests performed on some typical organic solvents using our recently proposed algal biosensor (Cho et al 2008b). The principle of our apparatus was the measurement of the algal photosynthetic activity based on oxygen production when algal cells are exposed to various concentrations of toxicants.…”

Pesticides and Herbicides

“…studied the toxicity of a mixture of six organophosphorus pesticides to the luminescent bacterium Q67. All of the mixture toxicities observed were similar to the toxicities predicted by using the concentration addition (CA) model, but the mixture toxicities also correlated well with those predicted by the independent action (IA) model at low concentrations.Toxicity Assays Cho et al (2008a). constructed a systematic biosensor for estimating the toxicity of toxicants based on photosynthetic measurements in Selenastrum capricornutum cells.…”