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| Author(s): |
Juliana Galan Viana
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT) |
| Defense date: | 2020-02-12 |
| Examining board members: |
André Luiz Meleiro Porto;
Eduardo Bessa Azevedo;
Simone Possedente de Lira
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| Advisor: | André Luiz Meleiro Porto |
| Abstract | |
<span style=\"font-weight: 400;\">Brazil is the largest consumer of pesticides in the world and the economic development in the country is mainly focused on agricultural activities, being the largest exporter of sugar and the second largest exporter of soybeans in the world scenario. In addition, citrus, corn, cotton and tomato crops stand out, so that the application of pesticides in the fight against beings considered harmful to crops is effective. However, indiscriminate use of pesticides can result in accumulation in environmental compartments, water contamination problems, to interfere with the longevity of non-target organisms, among other problems. Thus, studying the degradation of pesticides is of great importance and relevance today and this work aimed to study the biodegradation of pesticides Bifenthrin and Fipronil by bacteria of the genus <span style=\"font-weight: 400;\">Bacillus<span style=\"font-weight: 400;\"> isolated from leaves of orange culture. Bifenthrin is a pyrethroid-classified pesticide widely used in different crops. Screening of the 8 bacterial strains was performed and by high performance liquid chromatography (HPLC-UVis) analysis, Bifenthrin biodegradation was found to be 79% to 88% by the bacteria identified as <span style=\"font-weight: 400;\">B. pseudomycoides<span style=\"font-weight: 400;\"> (2RF2C, 3RF2C, 4RF1C and 4RF2C) and the bacteria <span style=\"font-weight: 400;\">B. amyloliquefaciens<span style=\"font-weight: 400;\"> (RFD1C), <span style=\"font-weight: 400;\">B. safensis<span style=\"font-weight: 400;\"> / <span style=\"font-weight: 400;\">B. pumilus<span style=\"font-weight: 400;\"> (2RF1C), <span style=\"font-weight: 400;\">B. aryabhattai<span style=\"font-weight: 400;\"> / <span style=\"font-weight: 400;\">Bacillus <span style=\"font-weight: 400;\">sp. (2RF3C), <span style=\"font-weight: 400;\">B. megaterium<span style=\"font-weight: 400;\"> (RF1C) showed a Bifenthrin biodegradation between 25% and 38%. The bacterium <span style=\"font-weight: 400;\">B. pseudomycoides<span style=\"font-weight: 400;\"> (4RF1C) showed a 79% degradation of Bifenthrin and was selected for a replicate experiment so that possible biodegradation products were isolated and identified. Using the column chromatography technique it was possible to identify methyl 4-hydroxybenzoate, a possible metabolite produced by the bacterium <span style=\"font-weight: 400;\">B. pseudomycoides<span style=\"font-weight: 400;\"> (4RF1C). Gas chromatography-mass spectrometry (GC-MS) analyzes identified the compounds 4-di-<span style=\"font-weight: 400;\">tert<span style=\"font-weight: 400;\">-butylphenol, 1-nonadecene, <span style=\"font-weight: 400;\">N<span style=\"font-weight: 400;\">-phenethylacetamide and 1,4-diisopropylbenzene in reactions with Bifenthrin. A hydrolysis reaction of Bifenthrin by KOH was performed and the reaction products (alcohol BF-OH<span style=\"font-weight: 400;\"> and acid BF-COOH<span style=\"font-weight: 400;\">) were analyzed by HPLC-Uvis to verify the presence of these compounds in the reactions between bacteria and Bifenthrin. Then, a reaction was performed using alcohol BF-OH<span style=\"font-weight: 400;\"> with the bacterium <span style=\"font-weight: 400;\">B. pseudomycoides <span style=\"font-weight: 400;\">(4RF1C) to observe possible biodegradation products. This reaction was performed at 3 and 5 days and the percentage of alcohol BF-OH<span style=\"font-weight: 400;\"> consumption was 14% and 17%, respectively, and it was not possible to observe bands of biodegradation products for alcohol BF-OH<span style=\"font-weight: 400;\">. A consortium experiment employing the 8 bacterial strains showed that the percentage of biodegradation of the pesticide Bifenthrin was 51%. Fipronil is a pyrazole and has applicability as herbicide, insecticide, fungicide and acaricide. A screening with 8 bacterial strains was used to verify the degradability of the pesticide Fipronil by the microorganisms and, among the strains, the bacteria <span style=\"font-weight: 400;\">B. amyloliquefaciens<span style=\"font-weight: 400;\"> (RFD1C) and <span style=\"font-weight: 400;\">B. aryabhattai<span style=\"font-weight: 400;\"> / <span style=\"font-weight: 400;\">Bacillus<span style=\"font-weight: 400;\"> sp. (2RF3C) presented the lowest concentration of Fipronil after 5 days of reaction with 93% and 91% biodegradation or biotransformation, that is, they were the microorganisms responsible for the higher consumption of the pesticide in liquid medium. An experiment to evaluate the decay of the concentration of Fipronil pesticide at 1, 3 and 5 days was also performed, and a consortium experiment employing 8 bacterial strains showed that the percentage of biodegradation of the pesticide Fipronil was 81%. CG-MS analyzes identified several compounds including squalene terpene, 1<span style=\"font-weight: 400;\">H<span style=\"font-weight: 400;\">-indole, cyclo (Pro-Leu), <span style=\"font-weight: 400;\">N<span style=\"font-weight: 400;\">-phenethylacetamide, 5-hexyl dihydrofuran-2-(3<span style=\"font-weight: 400;\">H<span style=\"font-weight: 400;\">)-one, 1,3-diisopropylbenzene and 1,4-diisopropylbenzene. Analyzes on the high-resolution mass spectrometer coupled to the ultra-high performance liquid chromatograph (UPLC-HRMS) were performed and possible biotransformation metabolites of Bifentrin and Fipronil sulfone from Fipronil oxidation were observed. It is also noteworthy that squalene terpene was identified, possibly due to the association between citrus culture and associated microorganisms. In all experiments control reactions were performed in the absence of pesticide and showed good recovery when quantified. In all experiments control reactions were performed in the absence of pesticide and showed good recovery when quantified. An experiment was also conducted to evaluate the final recovery of both Bifentrhrin and Fipronil to obtain a 96% final recovery for both pesticides. Finally, this study showed that bacteria of the genus <span style=\"font-weight: 400;\">Bacillus<span style=\"font-weight: 400;\"> isolated from orange leaves were important in the degradation of pesticides Bifenthrin and Fipronil used in different stages of the crops in which they are applied. (AU) | |
| FAPESP's process: | 17/24429-7 - Biodegradation of bifenthrin and fipronil pesticides used in the orange cultivation by bacteria |
| Grantee: | Juliana Galan Viana |
| Support Opportunities: | Scholarships in Brazil - Master |