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Caracterização de consórcios microbianos ambientais enriquecidos com um fungicida fluorado persistente
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Abstract(s)
A utilização de pesticidas fluorados levanta preocupações ambientais devido à elevada estabilidade das ligações C–F, que dificulta a sua degradação e favorece a persistência em solos e ecossistemas aquáticos. O mefentrifluconazol, fungicida triazólico fluorado de uso agrícola, representa um exemplo pela sua elevada recalcitrância e potencial impacto ecotoxicológico. Este projeto de estágio integra-se no âmbito do Mestrado em Engenharia Química do Instituto Superior de Engenharia do Porto (ISEP) e foi desenvolvido no Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR). O estudo centrou-se na caracterização de
consórcios microbianos provenientes de rizossedimentos estuarinos, enriquecidos com mefentrifluconazol. As hipóteses de trabalho consideraram que (i) estes consórcios poderiam adaptar-se seletivamente ao fungicida, adquirindo capacidade para a sua biodegradação e defluorinação; (ii) que a presença de co-substratos (acetato de sódio ou 1H-1,2,4-triazol) influenciaria a dinâmica microbiana; (iii) e que a eficiência do processo dependeria da
concentração inicial do poluente. Através da sequenciação massiva do gene 16S rRNA, observaram-se alterações
significativas ao longo dos ciclos de enriquecimento, incluindo a redução da diversidade alfa inicial e a emergência de géneros adaptados à pressão seletiva do mefentrifluconazol, como Azospirillum, Methyloversatilis, Pseudarcobacter, Niveispirillum, Paracoccus, Methylobacterium e Hyphomicrobium. A viabilidade dos consórcios criopreservados foi confirmada em ensaios de cultura líquida, com libertação de fluoreto como indicador da defluorinação. Ensaios cinéticos demonstraram eficiências decrescentes de defluorinação (93,0%, 35,1%, 1,8% e 0,9% para 1, 3, 5 e 10 mg/L, respetivamente, após 21 dias), ajustando-se melhor ao modelo de primeira ordem,
com uma taxa de degradação de 0,042 ± 0,007 dia⁻¹ e um tempo de semi-vida de 16,7 dias para 1 mg/L de fungicida. Este trabalho contribui para o avanço do conhecimento sobre a potencialidade de consórcios microbianos ambientais na biotransformação de fungicidas fluorados emergentes e reforça a aplicabilidade da seleção artificial como ferramenta para desenvolver estratégias de biorremediação mais eficazes.
The use of fluorinated pesticides raises environmental concerns due to the high stability of C–F bonds, which hinders their degradation and promotes persistence in soils and aquatic ecosystems. Mefentrifluconazole, a fluorinated triazole fungicide widely applied in agriculture, exemplifies this issue because of its pronounced recalcitrance and potential ecotoxicological impact. This internship project was carried out within the framework of the Master’s Degree in Chemical Engineering at the Instituto Superior de Engenharia do Porto (ISEP) and developed at the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR). The study focused on the characterization of microbial consortia from estuarine rhizosediments enriched with mefentrifluconazole. The working hypotheses considered that (i) these consortia could selectively adapt to the fungicide, acquiring the ability for its biodegradation and defluorination; (ii) the presence of co-substrates (sodium acetate or 1H-1,2,4-triazole) would influence microbial dynamics; and (iii) the efficiency of the process would depend on the initial pollutant concentration. High-throughput sequencing of the 16S rRNA gene revealed significant shifts throughout the enrichment cycles, including an initial decrease in alpha diversity followed by the emergence of genera adapted to the selective pressure of mefentrifluconazole, such as Azospirillum, Methyloversatilis, Pseudarcobacter, Niveispirillum, Paracoccus, Methylobacterium, and Hyphomicrobium. The viability of cryopreserved consortia was confirmed in liquid culture assays, with fluoride release used as an indicator of defluorination. Kinetic experiments showed decreasing defluorination efficiencies (93.0%, 35.1%, 1.8%, and 0.9% for 1, 3, 5, and 10 mg/L, respectively, after 21 days), with the first-order kinetic model providing the best fit, yielding a degradation rate of 0.042 ± 0.007 day⁻¹ and a half-life of 16.7 days at 1 mg/L. This work contributes to advancing knowledge on the potential of environmental microbial consortia in the biotransformation of emerging fluorinated fungicides and highlights the applicability of artificial selection as a tool for developing more effective bioremediation strategies.
The use of fluorinated pesticides raises environmental concerns due to the high stability of C–F bonds, which hinders their degradation and promotes persistence in soils and aquatic ecosystems. Mefentrifluconazole, a fluorinated triazole fungicide widely applied in agriculture, exemplifies this issue because of its pronounced recalcitrance and potential ecotoxicological impact. This internship project was carried out within the framework of the Master’s Degree in Chemical Engineering at the Instituto Superior de Engenharia do Porto (ISEP) and developed at the Interdisciplinary Centre of Marine and Environmental Research (CIIMAR). The study focused on the characterization of microbial consortia from estuarine rhizosediments enriched with mefentrifluconazole. The working hypotheses considered that (i) these consortia could selectively adapt to the fungicide, acquiring the ability for its biodegradation and defluorination; (ii) the presence of co-substrates (sodium acetate or 1H-1,2,4-triazole) would influence microbial dynamics; and (iii) the efficiency of the process would depend on the initial pollutant concentration. High-throughput sequencing of the 16S rRNA gene revealed significant shifts throughout the enrichment cycles, including an initial decrease in alpha diversity followed by the emergence of genera adapted to the selective pressure of mefentrifluconazole, such as Azospirillum, Methyloversatilis, Pseudarcobacter, Niveispirillum, Paracoccus, Methylobacterium, and Hyphomicrobium. The viability of cryopreserved consortia was confirmed in liquid culture assays, with fluoride release used as an indicator of defluorination. Kinetic experiments showed decreasing defluorination efficiencies (93.0%, 35.1%, 1.8%, and 0.9% for 1, 3, 5, and 10 mg/L, respectively, after 21 days), with the first-order kinetic model providing the best fit, yielding a degradation rate of 0.042 ± 0.007 day⁻¹ and a half-life of 16.7 days at 1 mg/L. This work contributes to advancing knowledge on the potential of environmental microbial consortia in the biotransformation of emerging fluorinated fungicides and highlights the applicability of artificial selection as a tool for developing more effective bioremediation strategies.
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Keywords
Mefentrifluconazole Defluorination Co-metabolism Biodegradation kinetics Artificial selection Mefentrifluconazol Defluorinação Co-metabolismo Cinética de biodegradação Seleção artificial