Simultaneous natural attenuation of Cr(VI) and nitrate in the hyporheic zone sediments from an upstream tributary of the Jinsha River in the Sichuan Basin.

The coexistence of hexavalent chromium (Cr(VI)) and nitrate (NO3-) in groundwater and surface water presents a considerable challenge for the natural attenuation of these two contaminants because their interactions in nature remain contentious. This study investigated the interplay between Cr(VI) and NO3- in hyporheic zone (HZ) sediments by integrating Cr(VI) reduction kinetics, NO3- transformation, microbial community structure, and a three-rate model. The concurrent natural attenuation of Cr(VI) and NO3- in the sediments was significantly influenced by their initial concentrations and redox conditions. The reduction of low concentrations of Cr(VI) (37.1 and 96.2 µM) was slightly enhanced by NO3-, while inhibitory effects were observed at high concentrations of Cr(VI) (200.0 µM). However, except for an initial low concentration of Cr(VI) (37.1 µM) and NO3- (450 µM), the reduction of NO3- was adversely affected by Cr(VI). The reduction rates and efficiencies of Cr(VI) and NO3- were noticeably lower under aerobic conditions than under anaerobic conditions. This phenomenon can be attributed to the presence of O2, which decreased the selectivity of sediments-associated Fe(II) towards Cr(VI) and NO3- and induced alterations in the microbial community structure, leading to subsequent changes in NO3- transformation. Furthermore, the three-rate model represents a robust approach for elucidating the reduction of Cr(VI) in the presence of co-contaminants, such as NO3- contamination under diverse redox conditions. This study provides further insights into the interaction mechanism between Cr(VI) and NO3- within the HZ, necessitating the consideration of the microbial toxicity of Cr(VI) and electron competition among Cr(VI), NO3-, and O2.

Transcriptomic analysis and oxidative stress induced by sodium dichloroisocyanurate in the intestine of Phascolosoma esculenta.

Sodium dichloroisocyanurate (NaDCC, C3Cl2N3NaO3) is a solid chlorine-containing product that is widely used as a disinfectant in living environments, which has potential toxic effects on human and rats. Phascolosoma esculenta is a species native to the southeast coast of China and can be used as an indicator organism. In the present study, 150 P. esculenta were used to determine the LC50 of NaDCC for P. esculenta, then 100 P. esculenta were used to analysis the change of histopathology, oxidative stress and transcriptome after NaDCC exposure. The results showed that the LC50 of NaDCC for 48 h was 50 mg/L. NaDCC stress induced pathological events in P. esculenta, including blisters, intestinal structural damage and epithelial cell ruptured or even loss. The highest and lowest intestinal activity of superoxide dismutase in individual survivors was detected at 12 h and 72 h, respectively. Malondialdehyde levels in the intestine declined gradually from 3 h and increased at 9 h, and peaked at 12 h. Total antioxidant capacity declined at 3 h and dropped below the levels of control group after 9 h. Transcriptome sequencing analysis yielded a total of 48.65 Gb of clean data. A total of 34,759 new genes were found including 957 differentially expressed genes (DEGs). The DEGs were significantly enriched in ferroptosis, response to chemicals, response to stress, immune system, ion transport, cell death, oxidation-reduction, cellular homeostasis, protein ubiquitination, and protein neddylation. Additionally, the levels of detoxification enzymes, such as glutathione-S-transferase, cytochrome P450, ABC, UDP-glycosyltransferase and SLC transporters of endogenous and exogenous solutes were significantly changed. Overall, the results provide reference for reasonable use of disinfectants during farming, and also provide insight into the mechanisms related to NaDCC toxicity in P. esculenta.

MIXed plastics biodegradation and UPcycling using microbial communities: EU Horizon 2020 project MIX-UP started January 2020.

This article introduces the EU Horizon 2020 research project MIX-UP, "Mixed plastics biodegradation and upcycling using microbial communities". The project focuses on changing the traditional linear value chain of plastics to a sustainable, biodegradable based one. Plastic mixtures contain five of the top six fossil-based recalcitrant plastics [polyethylene (PE), polyurethane (PUR), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS)], along with upcoming bioplastics polyhydroxyalkanoate (PHA) and polylactate (PLA) will be used as feedstock for microbial transformations. Consecutive controlled enzymatic and microbial degradation of mechanically pre-treated plastics wastes combined with subsequent microbial conversion to polymers and value-added chemicals by mixed cultures. Known plastic-degrading enzymes will be optimised by integrated protein engineering to achieve high specific binding capacities, stability, and catalytic efficacy towards a broad spectrum of plastic polymers under high salt and temperature conditions. Another focus lies in the search and isolation of novel enzymes active on recalcitrant polymers. MIX-UP will formulate enzyme cocktails tailored to specific waste streams and strives to enhance enzyme production significantly. In vivo and in vitro application of these cocktails enable stable, self-sustaining microbiomes to convert the released plastic monomers selectively into value-added products, key building blocks, and biomass. Any remaining material recalcitrant to the enzymatic activities will be recirculated into the process by physicochemical treatment. The Chinese-European MIX-UP consortium is multidisciplinary and industry-participating to address the market need for novel sustainable routes to valorise plastic waste streams. The project's new workflow realises a circular (bio)plastic economy and adds value to present poorly recycled plastic wastes where mechanical and chemical plastic recycling show limits.