Three enzyme based amperometric biosensors for biogenic amines were applied for meat spoilage monitoring. With diamine oxidase (EC 1.4.3.6), the total biogenic amine content was measured. Monoamine oxidase A (EC 1.4.3.4) was used for determination of tyramine, tryptamine and phenylethylamine content. Putrescine was selectively detected with putrescine oxidase (EC 1.4.3.10). The enzymes were separately co-immobilized on graphite electrodes with peroxidase and Os mediator (PVI7-dme-Os). A fast extraction method using special centrifugal separator was applied for pork and fish samples stored at different conditions. Although partial extraction was achieved, the results correlate with total biogenic amine content measured by HPLC method.
Transformation of pesticides in the environment is a highly complex process affected by different factors. Biological and physical-chemical factors may play a role in the degradation to variable extent. Photodecomposition might be regarded as one of the most crucial factors affecting the fate of pesticides. Therefore, our study focused on revealing specific details of the photolytic degradation of pesticides. The toxicity of the examined pesticides is well known; however, little information is available regarding their natural degradation processes. More detailed examinations are required to reveal the exact mechanism of the pesticide decomposition and the biological impacts of the degradates. Significance of this study is enhanced by the fact that decomposition of pesticides may result in the formation of toxic degradation products. The photolytic degradation of frequently applied pesticides (e.g., acetochlor, simazine, chlorpyrifos, and carbendazim) with different chemical structures was investigated. An immersible ultraviolet light source was applied to induce photodegradation. The degradation processes were followed by thin-layer chromatography and gas chromatography/mass spectrometry techniques. Electron ionization mass spectrometry was used to identify the degradation species. Detailed mechanisms of photolytic transformation were established by identification of each degradate. The photolytic degradation of pesticides of distinctive chemical character exhibited markedly different photodecomposition mechanisms. At least four degradation species were detected and identified in each case. Loss of alkyl, chloro, and hydroxyl groups as well as cleavage of alkyloxy, amide, amino-alkyl, and ester bonds might be regarded as typical decomposition patterns. Deamination and ring opening might be observed at the last stages of decomposition.
Our study aimed at acquiring information about the biological effect of pesticides and their degradates produced by UV-treatment on microbiological activity. Five photosensitive pesticides (carbendazim, acetochlor, simazine, chlorpyrifos, EPTC) and six representative soil microbes (Bacillus subtilis, Pseudomonas fluorescens, Mycobacterium phlei, Fusarium oxysporum, Penicillium expansum, Trichoderma harzianum) were applied throughout our model experiments. The antimicrobial effects of the pesticides and their degradates were assessed with filter paper disk method. The antimicrobial effect of the degradation products exhibited marked differences in terms of pesticide types, irradiation time, and the test organisms. Acetochlor and its photolytic degradation products were found to be more toxic to bacteria than fungi. All the three bacteria proved to be sensitive to the basic compound and its degradation products as well. The end product of carbendazim was weakly antibacterial against P. fluorescens and B. subtilis but strongly antifungal against T. harzianum. Chlorpyrifos and its end product inhibited neither test organisms, but the degradates hindered the growth of four of them. The basic compound of EPTC and the degradates of simazine exhibited significant toxicity to the test bacteria. It might be claimed that the pesticide photodegradation may result in significant changes in soil microbiota, as well as formation of biologically harmful degradates.
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