The Study Of Luminescent Phosphoreum Biosensors For Seawater Toxicity Biomonitoring And Rapid Determining Of Pesticide Residues On Vegetables

Rapid and continuous detection of environmental contaminants is important for protecting natural environments and public health, and for managing waster treatment systems. Although physicochemical methods have traditionally been employed for analyzing contaminants, monitoring using biological indicators has received increasing attention over the last few years for measuring toxic and bioavailable pollutants. Photobacterium phosphoreum is a marine bacterium, which is used extensively as a bioluminescent indicator of pollutants, where the presence of toxicants diminishes light output. Coupling biological detection systems with optical biosensors for environmental monitoring and vegetable pesticides residues combine rapid response times, low costs and improved reproducibility.This dissertation consists of three parts: 1.Literature summary, 2. Methods and principles, 3. The manufacture and investigation of Photobacterial biosensor in biomonitoring and Characterization of Toxicity of seawater and in quick determination of the pesticides residues in vegetables.In the first chapter, the definition, the origination ,the current situation and the characterization of the biosensor technology, especially focused on its application in biomonitoring the toxicity of seawater are reviewed. Furthermore, the article also summarized the general methods of quick determination of the pesticides residues.In the second part, the kinetic method of determining the toxicity of water using Photobacterium is described. Due to the instability of the photobacterium phosphoreum, it is essential to choose a luminescent stable standard and calibrate the relative luminescent intensity of standard solutions in the current methods of determining the toxicity of water, which made the on-line determination unavailable. Furthermore, the preservation of the bacteria is the most difficult task in this field. Our method utilizes quenching of the luminescent bacterium and an on-line biosensor system. The slope of the light decay plot with time is determined is an indication of relative toxicity. It is anticipated that this method is useful for biosensor monitoring chemical hazards.The third part of this paper is about the two applications of this method. Two kinds of photobacterium biosensor and their applications are investigated.The first application is to manufacture a liquid photobacterial biosensor to monitoring the real toxicity situation of the seawater. The biosensor system is composed of a luminescent spectrometer, flow chamber and bacterial culture reservoir. Coupling the spectrometer and the flow chamber with an optical fiber for collecting light out from the chamber when bacterium cells were added into the seawater in the chamber. The experimental introduces the system composing, the reagents be used and the flow process of determination. The optimizing parameter, the life-time experiment and the determination of 4 heavy metals, pesticides and other toxicants are reported. Finally,The biosensor system is brought to the fish cultured net-cage to determining on line. The results are satisfactory.Another application is about the quick determination of the pesticide residues in vegetable using the photobacterium membrane biosensor. The research contents are basically identical to the first application. In this work, the most important task is to choose the appropriate method to make the membrane. We tested the different formula and their lifetime to choose the optimum for the application.