Occurrence of Natural and Synthetic Micro-Fibers in the Mediterranean Sea: A Review.

Among microplastics (MPs), fibers are one of the most abundant shapes encountered in the aquatic environment. Growing attention is being focused on this typology of particles since they are considered an important form of marine contamination. Information about microfibers distribution in the Mediterranean Sea is still limited and the increasing evidence of the high amount of fibers in the aquatic environment should lead to a different classification from MPs which, by definition, are composed only of synthetic materials and not natural. In the past, cellulosic fibers (natural and regenerated) have been likely included in the synthetic realm by hundreds of studies, inflating "micro-plastic" counts in both environmental matrices and organisms. Comparisons are often hampered because many of the available studies have explicitly excluded the micro-fibers (MFs) content due, for example, to methodological problems. Considering the abundance of micro-fibers in the environment, a chemical composition analysis is fundamental for toxicological assessments. Overall, the results of this review work provide the basis to monitor and mitigate the impacts of microfiber pollution on the sea ecosystems in the Mediterranean Sea, which can be used to investigate other basins of the world for future risk assessment.

Combined action of a bacterial monooxygenase and a fungal laccase for the biodegradation of mono- and poly-aromatic hydrocarbons.

The combined action of a wide substrate range toluene o-xylene monooxygenase from Pseudomonas sp. OX1, able to convert many aromatic compounds into mono- and di-hydroxylated derivatives, and fungal laccases from Pleurotus ostreatus which oxidize these hydroxylated products yielding polymers with reduced toxicity is described. This strategy permits to overcome many of the substrate specificity problems and dead end toxic products formation generally encountered in complex bacterial biodegradation pathways. Toluene and naphthalene degradations were tested as representative of mono- and poly-aromatic pollutants. The combined biological action was optimized in micellar and microemulsion systems able to increase the bioavailability of the hydrophobic aromatic pollutants. This approach allows efficient hydroxylations of hydrophobic substrates thus favoring the further action of fungal oxidases.

Legacy persistent organic pollutants including PBDEs in the trophic web of the Ross Sea (Antarctica).

The ecological features of the Ross Sea trophic web are peculiar and different from other polar food webs, with respect to the use of habitat and species interactions; due to its ecosystem integrity, it is the world's largest Marine Protected Area, established in 2016. Polar organisms are reported to bioaccumulate lipophilic contaminant, viz persistent organic pollutants (POPs). Legacy POPs and flame retardants (polybrominated diphenyl ethers, PBDEs) were studied in key species of the Ross Sea (Euphausia superba, Pleuragramma antarctica) and their predators (Dissostichus mawsoni, Pygoscelis adeliae, Aptenodytes forsteri, Catharacta maccormicki, Leptonychotes weddellii). Gaschromatography revealed the presence of PCBs, HCB, DDTs, PBDEs in most of the samples; HCHs, dieldrin, Eldrin, non-ortho PCBs, PCDDs, PCDFs were detected only in some species. The average ∑PBDEs was 0.19-1.35 pg/g wet wt in the key-species and one-two order of magnitude higher in the predators. Penguins and skuas from an area where a long-term field camp is located showed higher BDE concentrations. The ΣDDTs was higher in the Antarctic toothfish (20 ± 6.73 ng/g wet wt) and in the South Polar skua (5.911 ± 3.425 ng/g wet wt). The TEQs were evaluated and the highest concentration was found in the Weddell seal, due to PCB169, 1,2,3,4,7,8-HxCDF, and 2,3,4,6,7,8-HxCDF. There was no significant relationship between the trophic level and the POP concentrations. Although low concentrations, organisms of the Ross Sea trophic web should be further studied: lack of information on some ecotoxicological features and human impacts including global change may distress the ecosystem with unpredictable effects.

Biotransformation of chloroaromatics: the impact of bioavailability and substrate specificity.

The effect of surfactants on the biodegradation of mono-aromatic hydrocarbons such as benzene, chlorobenzene and 1,2-dichlorobenzene by an Escherichia coli JMI09(MI) recombinant strain, carrying a gene cluster containing the genes for benzene dioxygenase, cis-benzene dihydrodiol dehydrogenase, and catechol 2,3-dioxygenase from Pseudomonas putida ML2, has been investigated. We observed that the efficiency of the benzene dioxygenase catalyzed conversions to cis-dihydrodiols depends on the balance among real substrate specificity, bioavailability, and toxicity effects of highly concentrated aromatic hydrocarbons. The utilization of non ionic surfactants makes it possible to partly overcome the limiting step of biodegradation processes for scarcely water soluble hydrocarbons hindered by their limited bioavailability.Furthermore the cis-benzene dihydrodiol dehydrogenase and the extradiol catechol 2,3-dioxygenase, which in the presently analyzed biodegradative pathway should further degrade the pollutants, are known, the first to be selectively specific for the (lR,2R)-dihydrodiol derivative which is not produced by the benzene dioxygenase, the second, to be dead-end inhibited by the corresponding chlorinated catechois. In the present example this results in the accumulation of the corresponding chlorinated cis-dihydrodiols which can be useful for asymmetric synthesis.On the other hand the practical utilization of the system for bioremediation purposes requires the efficient conversion of the chlorinated catechols by specific intradiol ring-cleaving dioxygenases, the crystal structures of some of these last enzymes are currently under analysis in our laboratory to understand the structuralfunctional correlations. Preliminary data show overall structures similar to the catechol 1,2-dioxygenase from Acinetobacter sp. ADP1 thus suggesting that the substrate specificity differences are mainly related to subtle differences in the catalytic site.