Browsing by Author "Maia, Tiago"
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- Development of a bioremediation system for the removal of PFAS from aquatic environmentsPublication . Pinto, Ana Sofia; Neves, David M. B.; Maia, Tiago; Mucha, Ana Paula; Almeida, C. Marisa R.; Martins, Pedro; Lanceros-Mendez, Senetxu; Alexandrino, Diogo A. M.; Alexandrino, DiogoAmong the many pollutants that afflict aquatic ecosystems, PFAS (per- and polyfluoroalkyl substances) stand out due to their distribution, environmental persistence and ecotoxicity. Currently, there are no suitable remediation technologies capable of mitigating PFAS-related pollution in these ecosystems. Yet, the combination of nanophotocatalysis (NPC) and bioremediation (BRMD) may prove useful in combating PFAS aquatic pollution. NPC has shown promising results for the breakdown of persistent pollutants, while BRMD processes can benefit from the high degree of redundancy and promiscuity of bacterial catabolism to efficiently degrade various pollutants and their sub-products. As such, this work aims to develop an efficient BRMD unit, based on a synthetic bacterial consortium with orthogonal defluorination capacity, and explore its potential to act as a secondary water treatment step in tandem with a TiO2-based NPC treatment, to remove PFAS from aquatic matrices. The first development step, currently ongoing, is set on screening different bacterial strains enriched with fluorinated pollutants, petroleum hydrocarbons or cyanotoxins. This sorting is being achieved by validating the degradative capabilities of the strains based on their bacterial growth and defluorination performances. So far, these preliminary tests led to the selection of two prospective consortium members, Delftia acidovorans MFA5 and Labrys portucalensis F11, based on their capacity to defluorinate 50 mgL-1 of fluoroacetate and fluorobenzene in 8 days, respectively. Once all strains are selected and their co-cultivation dynamics are ascertained, a synthetic bacterial consortium will be assembled and tested as a BRMD step coupled to a primary NPC treatment against two different PFAS in quasi-real aquatic matrices.
- Exploring the possible link between fluoride sensitivity and bacterial defluorinationPublication . Maia, Tiago; Carvalho, Maria F.; Alexandrino, Diogo A. M.; Alexandrino, DiogoFluoorganic compounds are ubiquitous environmental pollutants due to their widespread use and high environmental persistence, mostly attributed to the stability of their carbon-fluoride bonds. The biotransformation of these compounds has been observed in some microorganisms, but defluorination (cleavage of carbon-fluorine bonds) remains the limiting step. Intracellular accumulation of fluoride occurs during microbial defluorination, which can cause several toxic effects. This work hypothesizes that intracellular fluoride stress may potentially affect the defluorination process in bacteria, limiting this critical catabolic step for the eventual mineralization of fluoroorganic pollutants. Fluoride sensitivity was first ascertained in defluorinating bacteria Labrys portucalensis F11 and Delftia acidovorans MFA5 (known degraders of fluorobenze1 and fluoroacetate2, respectively), with an Escherichia coli strain as the non-defluorinating control. Sensitivity was tested for increasing concentrations of f luoride (0-0.6 mM NaF) both in oligotrophic (minimal salts medium with acetate) and mesotrophic media (Nutrient Broth), based on bacterial growth inhibition for 48 hours at 28 ºC. After ascertaining their sensitivity thresholds, these strains are now being tested for their defluorination ability, against their preferred fluorinated substrates, when exposed to the NaF concentration with the highest observed growth inhibition. Results showed that fluoride stress was more severe in oligotrophic media, with 0.4 mM NaF presenting the highest growth inhibition among tested strains. Strain MFA5 was also shown to be the least sensitive to fluoride, while F11 was the most affected. Conclusions: Fluoride can exert cytostatic effects even in bacterial strains with proven ability to biodegrade fluorinated compounds. These results will allow to enlighten the ties between fluoride sensitivity and bacterial defluorination, thus broadening the knowledge on influencing factors of a critical catabolic reaction.