| With the great increase of human industrial production and agricultural activity,more and more toxicants such as heavy metal ions and pesticides have been into waterbodies causing severe contamination. These substances will form a new contaminantthrough complex physical, chemical, and biological transformation process. Somepollutants maybe enter the food chain and further accumulate in living being’s body.Eventually the various kinds of biotoxicity effects will produce and influence thecreature. Acute biotoxicity tests can indicate the damage caused by pollutantscontacting with the body in a short time and provide early warning for environmentalpollution.Biosensor is very popular and in the field of environmental monitoring because ofits small size, fast response and in situ for online monitoring. E. coli is a representativegram-negative prokaryotes and yeast is a representative enkaryotes. In this paper wetook Escherichia coli and Saccharomyces cerevisiae as a model microorganismrespectively, developed three kinds of whole-cell microbiosensor based on effectiveimmobilization technology, optimized the experimental parameters and then determinedthe acute biotoxicity effects of heavy metal ions, phenols, pesticides and so on.Microbial immobilization technology research showed that the whole-cell biosensorshad a good toxic analysis performance when we respectively used grafting polymerPVA-g-P(4-VP), PVA-Na2SO4sol, PVA-alginate hybrid sol to fix microorganism.Furthermore, we used the cell walls pretreatment technology to yeast and effectivelyimproved the detection sensitivity.E.coli microbial electrode for biosensor was prepared and their performance foracute biotoxicity determination of heavy metals (Cu2+, Zn2+and Pd2+), Ametryn andAcephate by single or mixture was studied preliminarily. To the same toxicant, weobtained the different biotoxicity analysis results when we use the different trainingperiods microbial cells. A measuring condition with E.coli in logarithmic phase16h,p-benzoquinone as mediator and pH6-8was optimized. The experimental resultsrevealed that the inhibitory effects of toxicants to E. coli ’s respiration can be ranked in adecreasing order: Cu2+> Zn2+> Pd2+, Ametryn> Acephate, which are in accordancewith other ways, like the luminescent bacteria, fish, algae etc, RSD <5%. This methodis rapid, simple, sensitive, cheap and promising for wastewater monitoring on line.A disposable microbial film electrode immobilized with Saccharomyces cerevisiaewas studied for acute biotoxicity determination. S.cerevisiae cells were pretreated withalcohols before immobilization. In order to improve the sensitivity, we pretreated theyeast cells wall. Then their pretreated effects were investigated through observing themorphology change of yeast by atomic force microscopy (AFM), testing the biotoxicity of3,5-dichlorophenol (DCP), and detecting viability by flow cytometry (FCM) assay.The results revealed that the sensitive and stable response was when S.cerevisiaepretreated with30%ethanol16h, p-benzoquinone as a mediator and Ph7.0. In addition,the complex of PVA and sodium alginate solution crosslinked by CaCl2was selected asan entrapping agent to immobilize S.cerevisiae, forming a kind of porous polymericfilm. This porous structure could be in favor the substance diffusion. Especially, thisbiofilm is disposable and convenient for a next biotoxicity determination by change anew one. And it also has a strong toughness, good biological compatibility. Heavy ions,3,5-dichlorophenol (DCP), pesticide and actual water body etc were determined. Theexperimental results indicated that it can sensitively determine biotoxicity within30~40min, RSD <5%. This disposable amperometric microbial biosensor is a sensitive, rapid,reproducibility, convenient and cheap alternative to toxicity screening of wastewater.Through the above studies, the whole-cell biosensors we prepared based onelectrochemistry, which are steady, rapid, sensitive, and screening on line. So they havea broad application prospect. |
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