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- Biodegradation of polyethylene microplastics by the marine fungus zalerion maritimumPublication . Paço, Ana; Duarte, Kátia; Costa, João P. da; Santos, Patrícia S.M.; Pereira, R.; Pereira, M. E.; Freitas, Ana C.; Duarte, Armando C.; Rocha-Santos, Teresa A. P.Plastic yearly production has surpassed the 300milliontons mark and recycling has all but failed in constituting a viable solution for the disposal of plastic waste. As these materials continue to accumulate in the environment, namely, in rivers and oceans, in the form of macro-, meso-, micro- and nanoplastics, it becomes of the utmost urgency to find new ways to curtail this environmental threat. Multiple efforts have been made to identify and isolate microorganisms capable of utilizing synthetic polymers and recent results point towards the viability of a solution for this problem based on the biodegradation of plastics resorting to selected microbial strains. Herein, the response of the fungus Zalerion maritimum to different times of exposition to polyethylene (PE) pellets, in a minimum growth medium, was evaluated, based on the quantified mass differences in both the fungus and the microplastic pellets used. Additionally, molecular changes were assessed through attenuated total reflectance Fourier transform Infrared Spectroscopy (FTIR-ATR) and Nuclear Magnetic Resonance (NMR). Results showed that, under the tested conditions, Z. maritimum is capable of utilizing PE, resulting in the decrease, in both mass and size, of the pellets. These results indicate that this naturally occurring fungus may actively contribute to the biodegradation of microplastics, requiring minimum nutrients.
- Salinity induced effects on the growth rates and mycelia composition of basidiomycete and zygomycete fungiPublication . Venâncio, C.; Pereira, R.; Freitas, A. C.; Rocha-Santos, T. A. P.; Costa, J. P. da; Duarte, A. C.; Lopes, I.Soil salinization, as the combination of primary and secondary events, can adversely affect organisms inhabiting this compartment. In the present study, the effects of increased salinity were assessed in four species of terrestrial fungi: Lentinus sajor caju, Phanerochaete chrysosporium, Rhizopus oryzae and Trametes versicolor. The mycelial growth and biochemical composition of the four fungi were determined under three exposure scenarios: 1) exposure to serial dilutions of natural seawater (SW), 2) exposure to serial concentrations of NaCl (potential surrogate of SW); and 3) exposure to serial concentrations of NaCl after a period of pre-exposure to low levels of NaCl. The toxicity of NaCl was slightly higher than that of SW, for all fungi species: the conductivities causing 50% of growth inhibition (EC50) were within 14.9 and 22.0 mScm−1 for NaCl and within 20.2 and 34.1 mScm−1 for SW. Phanerochaete chrysosporium showed to be the less sensitive species, both for NaCl and SW. Exposure to NaCl caused changes in the biochemical composition of fungi, mainly increasing the production of polysaccharides. When fungi were exposed to SW this pattern of biochemical response was not observed. Fungi pre-exposed to low levels of salinity presented higher EC50 than fungi non-pre-exposed, though 95% confidence limits overlapped, with the exception of P. chrysosporium. Pre-exposure to low levels of NaCl also induced changes in the biochemical composition of the mycelia of L. sajor caju and R. oryzae, relatively to the respective control. These results suggest that some terrestrial fungi may acquire an increased tolerance to NaCl after being pre-exposed to low levels of this salt, thus, suggesting their capacity to persist in environments that will undergo salinization. Furthermore, NaCl could be used as a protective surrogate of SW to derive safe salinity levels for soils, since it induced toxicity similar or higher than that of SW.