The development of a biosensor for the detection of PS II herbicides using green microalgae
A PS II biosensor was developed using intact green algae of Chlorophyta. The biosensor was based on the ability of some herbicides (PS II herbicides) residue to inhibit the binding niche of primary electron donor/acceptor of Photosystem II, plastoquinone B (Os) at 01 heterodimer protein, causing an...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2006
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| Subjects: | |
| Online Access: | https://eprints.ums.edu.my/id/eprint/10111/1/24%20PAGES.pdf https://eprints.ums.edu.my/id/eprint/10111/2/FULLTEXT.pdf |
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| Summary: | A PS II biosensor was developed using intact green algae of Chlorophyta. The biosensor was based on the ability of some herbicides (PS II herbicides) residue to inhibit the binding niche of primary electron donor/acceptor of Photosystem II, plastoquinone B (Os) at 01 heterodimer protein, causing an increase of the chlorophyll fluorescence. Herbicideinduced chlorophyll-a fluorescence was correlated with the corresponding herbicide concentration to obtain a standard calibration curve for herbicide detection. The fluorescence yield was expressed as a rate of the fluorescence increase calculated mathematically from fitted curve of herbicide-induced fluorescence data using SigmaPlot and CurveFit Expert software. The fluorescence was recorded using a TD-700 fluorometer from Turner Design, USA. Six freshwater microalgae isolated from a lake near Likas Bay, Kola Kinabalu, Sabah were examined; Chlorella sp., Pediastrum sp., Kirchneriel/a sp., Coe/astrum sp., Scenedesmus dimorphus, and Selenastrum sp. Of all the species examined, Scenedesmus dimorphus was found to be the most suitable algae as a biosensor based on the following criteria; (1) highest growth rate, (2) easy to culture and maintain purity, and (3) sensitivity to low concentration of herbicide. Effects of culture age, temperature, solvents, sample matrix and pre-incubation of sample were examined to optimize the biosensor. Cell suspension at 14- days was found to be the best algal age especially when using Scenedesmus dimorphus. The correlations between fluorescence yields (expressed as the rate of fluorescence, {3) and concentration (a) of diuron, propanil and bromaci/ were a = 10A ((log {3- 0.536)/1.08), a = 10''-((log {3- 0. 3893 )/1. 1119) and a = 1 0"((log {3 - 0. 1678)/0. 7084), respectively. The detection range of diuron, propanil and bromacil were 1x1U3 mM - 1mM, 1x10-1 mM - 1 x101 mM and 1x10-1 mM - 1 x1a2 mM, respectively. The lowest detectable concentration of the biosensor was approximately 1 x 1 o-3 mM (2.33x1a2 μg/L), for diuron, 1x10-1 mM (2. 18x1a3 μg/L) for propanil and 1x1a1 mM (2.61x1d3 μg/L) bromacil. The biosensor can be used as an early warning system at present and offers a potential rapid, cheap and fast method for PS II herbicides detection in the future. |
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