Effects of Engineered Nanoparticles on the Assembly of Exopolymeric Substances from Phytoplankton

The unique properties of engineered nanoparticles (ENs) that make their industrial applications so attractive simultaneously raise questions regarding their environmental safety. ENs exhibit behaviors different from bulk materials with identical chemical compositions. Though the nanotoxicity of ENs has been studied intensively, their unintended environmental impacts remain largely unknown. Herein we report experimental results of EN interactions with exopolymeric substances (EPS) from three marine phytoplankton species: Amphora sp., Ankistrodesmus angustus and Phaeodactylum tricornutum. EPS are polysaccharide-rich anionic colloid polymers released by various microorganisms that can assemble into microgels, possibly by means of hydrophobic and ionic mechanisms. Polystyrene nanoparticles (23 nm) were used in our study as model ENs. The effects of ENs on EPS assembly were monitored with dynamic laser scattering (DLS). We found that ENs can induce significant acceleration in Amphora sp. EPS assembly; after 72 hours EN-EPS aggregation reached equilibrium, forming microscopic gels of ∼4–6 µm in size. In contrast, ENs only cause moderate assembly kinetic acceleration for A. angustus and P. tricornutum EPS samples. Our results indicate that the effects of ENs on EPS assembly kinetics mainly depend on the hydrophobic interactions of ENs with EPS polymers. The cycling mechanism of EPS is complex. Nonetheless, the change of EPS assembly kinetics induced by ENs can be considered as one potential disturbance to the marine carbon cycle

Chemical characterization and in vitro colonic fermentation of grape pomace extracts

[Background] Currently, there is growing interest in extracts derived from winery by‐products because of their beneficial health properties, which are associated with the presence of bioactive compounds. In this paper, we have carried out the chemical characterization and in vitro colonic fermentation of four grape pomace (GP) extracts rich in polyphenols and dietary fibre.[Result] Firstly, phenolic and dietary fibre composition of the GP extracts was determined. The highest individual phenolic concentrations corresponded to gallic and ellagic acids, followed by catechins and flavonols. The non‐digestible fibre fraction ranged from 66% to 83% of the GP extracts, which indicated that they mainly contained non‐digestible cell wall components. Secondly, when GP extracts were subjected to fermentation by faecal microbiota, a total of 16 bacterial phenolic metabolites were found in the fermented samples, confirming that polyphenols contained in the GP extracts were metabolized to different active metabolites by microbiota. In addition, the GP extracts tended to promote the growth of intestinal microbiota, although it was only significant for the Enterococcus group.[Conclusion] These findings, together with other information available in the literature, support the high added value of products obtained from winery by‐products.This work was funded by the Spanish MINECO (Projects INNPACTO IPT 2012‐0130‐060000, BFU2012‐35228, AGL2012‐40172‐C02‐01 and AGL2015‐64522‐C2‐R). IG‐S and BA‐D are the recipients of fellowships from the FPU‐MECD (FPU14/05760) and FPI‐MEC programme, respectively.Peer reviewe