Maria C. Leitão

Novel biocompatible cholinium-based ionic liquids—toxicity and biodegradability†

The synthesis, characterisation and toxicological assessment of a new group of environmentally friendly ionic liquids are presented. Focussing on the toxic effect of the anion, the ionic liquids were designed by combining the benign cholinium cation, [NMe3(CH2CH2OH)]+, with a range of linear alkanoate anions ([CnH2n+1CO2]−, n = 1-9), as well as two structural isomers (n = 3 or 4). The toxicity of these ionic liquids was evaluated using filamentous fungi as model eukaryotic organisms. Surprisingly, most of the tested species showed active growth in media containing extremely high ionic liquid concentrations, up to molar ranges in some cases. The biodegradability of these ionic liquids was assessed, and new biotechnological applications for them are proposed, e.g. as solvents for biopolymers. This study leads to the better understanding of the anion influence on the ionic liquid toxicity, but its core is the recognition that conscious design of ionic liquids can be used to deliver truly biocompatible salts without adversely affecting one of the most striking of their properties—their outstanding solvent ability.

Dissolution of cork biopolymers in biocompatible ionic liquids

Classically, the best attempts to separate suberin from cork biopolymers have resulted in low efficiency; here, we report a class of biocompatible and biodegradable cholinium-based ionic liquids, the cholinium alkanoates, which show a highly efficient and specific dissolution of the suberin domains from cork biopolymers.

Exploring fungal activity in the presence of ionic liquids

In this work, the toxicological assessment towards filamentous fungi (Penicillium sp.) as model eukaryotic organisms of sixteen ionic liquids (containing an imidazolium, pyridinium, or cholinium cation) is presented. Amongst these fungi are members which show much higher tolerance towards ionic liquids than any other microorganism so far studied. Furthermore, guided by the paradigm that the choice of an ionic liquid as catalyst can alter the outcome of a given chemical reaction, the ability of ionic liquids to alter the metabolic profile in fungi was studied. The metabolic footprint, as investigated by electrospray ionisation mass spectrometry, revealed that fungal cultures respond to specific ionic liquids by changing their cell biochemistry, resulting in an altered pattern of secondary metabolites.

Impact of ionic liquids on extreme microbial biotypes from soil

This work aims at identifying, amongst extreme soil biotypes at locations of high salinity and high hydrocarbon load, microbial strains able to survive short or long-term exposure to the presence of selected ionic liquids. We have evaluated the impact of ionic liquids on the diversity of the soil microbiota to identify which microbial strains have higher survival rates towards ionic liquids, and consequently those which might possibly play a major role in their biotic fate. To the best of our knowledge, this is the first study of this kind. Soils, from a region in Portugal (Aveiro) were sampled and the bacterial and fungal strains able to survive after exposure to high concentrations of selected ionic liquids were isolated and further characterised. We have mainly focused on two types of cations: imidazolium – the most commonly used; and cholinium – generally perceived as benign. The surviving microbial strains were isolated and taxonomically identified, and the ionic liquid degradation was analysed during their cultivation. The continuing exposure of the microbial strains to petroleum hydrocarbons is likely to be the basis for their acquired resistance to some imidazolium salts; also, the higher capacity of fungi – compared to bacteria – to grow, even during their exposure to these liquid salts, became evident in this study.

Screening pentachlorophenol degradation ability by environmental fungal strains belonging to the phyla Ascomycota and Zygomycota

Pentachlorophenol (PCP) bioremediation by the fungal strains amongst the cork-colonising community has not yet been analysed. In this paper, the co- and direct metabolism of PCP by each of the 17 fungal species selected from this community were studied. Using hierarchical data analysis, the isolates were ranked by their PCP bioremediation potential. Fifteen isolates were able to degrade PCP under co-metabolic conditions, and surprisingly Chrysonilia sitophila, Trichoderma longibrachiatum, Mucor plumbeus, Penicillium janczewskii and P. glandicola were able to directly metabolise PCP, leading to its complete depletion from media. PCP degradation intermediates are preliminarily discussed. Data emphasise the significance of these fungi to have an interesting potential to be used in PCP bioremediation processes.

Degradation pathway of pentachlorophenol by Mucor plumbeus involves phase II conjugation and oxidation–reduction reactions

Environmental pollution by pentachlorophenol (PCP) is a critical concern worldwide and fungal bioremediation constitutes an elegant and environment-friendly solution. Mucorales from the Zygomycota phylum are often observed to be competitive in field conditions and Mucor plumbeus, in particular, can efficiently deplete PCP from media. The pathway for PCP degradation used by this fungus has not been investigated. In this study, PCP-derived metabolites were identified by liquid chromatography coupled with quadrupole time-of-flight mass spectrometry, including tetra- and tri-chlorohydroquinones and phase II-conjugated metabolites. Amongst the latter are the previously reported glucose, sulfate and ribose conjugates, and identified for the first time in fungi sulfate-glucose conjugates. A PCP transformation pathway for M. plumbeus is proposed, which excludes the involvement of cytochrome P-450 and extracellular ligninolytic enzymes.

New branches in the degradation pathway of monochlorocatechols by Aspergillus nidulans: A metabolomics analysis

A collective view of the degradation of monochlorocatechols in fungi is yet to be attained, though these compounds are recognised as key degradation intermediates of numerous chlorinated aromatic hydrocarbons, including monochlorophenols. In the present contribution we have analysed the degradation pathways of monochlorophenols in Aspergillus nidulans using essentially metabolomics. Degradation intermediates herein identified included those commonly reported (e.g. 3-chloro-cis,cis-muconate) but also compounds never reported before in fungi revealing for 4-chlorocatechol and for 3-chlorocatechol unknown degradation paths yielding 3-chlorodienelactone and catechol, respectively. A different 3-chlorocatechol degradation path led to accumulation of 2-chloromuconates (a potential dead-end), notwithstanding preliminary evidence of chloromuconolactones and protoanemonin simultaneous formation. In addition, some transformation intermediates, of which sulfate conjugates of mono-chlorophenols/chlorocatechols were the most common, were also identified. This study provides critical information for understanding the role of fungi in the degradation of chlorinated aromatic hydrocarbons; furthering their utility in the development of innovative bioremediation strategies.