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- Comparison of cytochrome c with conventional biocatalysts in the degradation of environmental toxicantsPublication . Lagoa, Ricardo; Lopes, João M.; Rodrigues, J. Rui; Marques-da-Silva, DorindaPeroxidases and laccases are amongst the most attractive enzymes for the degradation of concerning pollutants like polycyclic aromatic hydrocarbons (PAHs) and organic dyes. In spite of the availability of high activity enzymes, their applicability is hindered by specificity and stability limitations in real environmental conditions, so more suitable biocatalysts are demanded. Cytochrome c (Cc) is best known as a protein electron carrier at mitochondria, but it also displays (pseudo-)peroxidase activity. In this work, we aimed to evaluate the potential of Cc as biocatalyst of PAHs’ and azo dyes’ degradation and compare it with two more conventional enzymes - plant peroxidases and fungi laccases. The studies were carried out with Cc from horse heart, horseradish peroxidase (HRP) and laccase from Trametes versicolor. The enzymes were tested with two major PAHs, anthracene and benzo[a]pyrene (BaP), and with methyl orange (MO) as a model azo dye. The enzyme-catalyzed oxidation of PAHs was determined by HPLC, and MO decolorization was followed in spectrophotometric kinetic assays. Several degradation studies were performed to assess the catalytic capacity at different pH and the effect of the redox mediator ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate)). Peroxidase reactions of HRP and Cc were initiated with 100 μM H2O2 (in media containing 100 μM DTPA as metal chelator). In pH 5 acetate buffer, the specific ABTS-oxidizing activity of Cc was much lower than that of laccase and HRP. However, these two enzymes lost almost all activity at pH 7, while Cc exhibited catalytic activity even at pH 8 (phosphate buffer). Decolorization assays showed laccase alone to be a weak catalyst of MO degradation, although addition of ABTS to the reaction media greatly accelerated the transformation. On the contrary, both HRP and Cc directly catalyzed MO decolorization, including at neutral pH, and the redox mediator offered no advantage. As for the PAHs, HRP and laccase catalysis benefited from the presence of ABTS in the media, but again Cc oxidized anthracene and BaP directly. Indeed, 24h incubation of BaP (1 mg/L) with Cc (0.1 mg/mL) resulted in the transformation of 70±4% of the PAH and generation of major reaction products different of the BaP quinones produced by laccase- and HRP-ABTS systems. This work disclosed catalytic properties of Cc different from laccase and HRP that are relevant for the design of new enzymatic remediation processes.
- Risk Communication for Decision-Making: The Role of Community-Contact, Nature-Positive Outcomes, and Risk-PerceptionPublication . Silva, DorindaAppropriate risk communication is extremely important to ensure stakeholder engagement and avoid fatigue, disengagement and inaction. Research shows that promotion of good news is likely to engage stakeholders and inspire action. Thus, to support properly informed risk communication and decision-making truer perceptions of risks and benefits are needed to enable nature-positive and community inclusivity outcomes. Environmental scientists are now tasked with promoting communication for decision making using methods that weigh harm caused against benefits delivered. Currently we face many planetary threats including from climate change as well as the influx of synthetic chemicals. Creating a nature-positive future in the face of these challenges requires positive messaging, measures, and metrics to guide, plan, assess and communicate regenerative development outcomes beyond toxicology, risk and damage assessment. As various stakeholders perceive risks differently it is of paramount importance to understand and predict how non-experts will react to risk, since the majority of this group are often not aware of the threats faced. Very often a lack of consideration is given to risk perception and behaviours across different stakeholders. Likewise contact with communities is challenging but can help to bridge the gap from scientific discovery to valuable knowledge translation into society, related to environmental risk. The session aims to clarify concepts, challenges, and innovative tools and methods for modelling, measuring, and communicating benefits weighed against risk. The session specifically focuses on accelerating restoration, climate security and preventative measures that have successfully been used to protect the environment and human health from harmful chemicals. Moreover, results of community engagement approaches will be presented allowing the possibility to discuss the associated opportunities and challenges of these communication strategies. Presentations should focus on case studies where community-engagement, nature-positive outcomes, and risk-perception are used to support risk communication for decision making, especially in the presence of limited or conflicting evidence. The session will disseminate valid policy, planning and communication tools and methods across various stakeholders including academics, NGOs, industry and policy makers and overall foster knowledge transfer across groups to deliver and manage regulatory solutions.