Maizatul Suriza Mohamed, (2006) The development of a biosensor for the detection of PS II herbicides using green microalgae. Masters thesis, Universiti Malaysia Sabah.
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 (QB) at D1 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 T0-700 fluorometer from Tumer Design, USA. Six freshwater microalgae isolated from a lake near Ukas Bay, Kota Kinabalu, Sabah were examined; Chlorella sp., Pediastrum sp., Kirchneriella sp., Coelastrum 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, p) and concentration (a) of diuron, propanil and bromacil were α= 10^ ((log β - 0.536)/1.08), α = 10^((log β- 0.3893)/1.1119) and a = 10^((log β - 0.1678)/0.7084), respectively. The detection range of diuron, propanil and bromacil were 1x10⁻³ mM - 1mM, 1x10⁻¹ mM - 1 x10¹ mM and 1x10⁻¹ mM - 1 x10²mM, respectively. The lowest detectable concentration of the biosensor was approximately 1 x 10⁻³ mM (2. 33x10² µg/L), for diuron, 1x10⁻¹ mM (2.18x10³ µg/L)) for propanil and 1x10⁻¹ mM (2.61x10³µg/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.
|Item Type:||Thesis (Masters)|
|Uncontrolled Keywords:||PS II, biosensor, Chlorophyta, microalgae, herbicides pollution, photosystem|
|Subjects:||R Medicine > R Medicine (General)|
|Divisions:||SCHOOL > School of Science and Technology|
|Deposited By:||IR Admin|
|Deposited On:||11 Dec 2014 14:16|
|Last Modified:||11 Dec 2014 14:16|
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