Industrial bioelectrochemistry for waste valorization: State of the art and challenges

Geobacter sulfurreducens strain 60473, a potent bioaugmentation agent for improving the performances of bioelectrochemical systems

Bioaugmentation with electrochemically active bacteria (EAB) has been suggested useful for improving the performance of bioelectrochemical systems (BESs) for sustainable energy generation, while its success is dependent on EAB introduced into the systems. Here we report on the isolation of a novel EAB, Geobacter sulfurreducens strain 60473, from microbes that colonized on an anode of a sediment microbial fuel cell. This strain is highly adhesive to graphite electrodes, forms dense biofilms on electrode surfaces, and generates high current densities in BESs. When microbial electrolysis cells (MECs) inoculated with paddy-field soil and fed starch as the major organic substrate were augmented with strain 60473, Geobacter bacteria predominantly colonized on anodes, and MEC performances, including current generation, hydrogen production and organics removal, were substantially improved compared to non-bioaugmented controls. Results suggest that bioaugmentation with electrode-adhesive EAB, such as strain 60473, is a promising approach for improving the performance of BESs, including MECs treating fermentable organics and biomass wastes.

Harnessing Pseudomonas putida in bioelectrochemical systems

Bioelectrochemical systems (BESs), a group of promising integrated systems that combine the advantages of biotechnology and electrochemical techniques, offer new opportunities to address environmental and energy challenges. Exoelectrogens capable of extracellular electron transfer (EET) are the critical factor enabling electrocatalytic activity in BESs. Pseudomonas putida, an aerobe widely used in environmental bioremediation, the biosynthesis of valuable chemicals, and energy bioproduction, has attracted much attention due to its unique application potential in BESs. This review provides a comprehensive understanding of the working principles, key factors, and applications of BESs using P. putida as the exoelectrogen. The challenges and perspectives for the development of BESs with P. putida as the exoelectrogen are also proposed and discussed.

Advancements in enzyme immobilization on magnetic nanomaterials: toward sustainable industrial applications

Enzymes are widely used in biofuels, food, and pharmaceuticals. The immobilization of enzymes on solid supports, particularly magnetic nanomaterials, enhances their stability and catalytic activity. Magnetic nanomaterials are chosen for their versatility, large surface area, and superparamagnetic properties, which allow for easy separation and reuse in industrial processes. Researchers focus on the synthesis of appropriate nanomaterials tailored for specific purposes. Immobilization protocols are predefined and adapted to both enzymes and support requirements for optimal efficiency. This review provides a detailed exploration of the application of magnetic nanomaterials in enzyme immobilization protocols. It covers methods, challenges, advantages, and future perspectives, starting with general aspects of magnetic nanomaterials, their synthesis, and applications as matrices for solid enzyme stabilization. The discussion then delves into existing enzymatic immobilization methods on magnetic nanomaterials, highlighting advantages, challenges, and potential applications. Further sections explore the industrial use of various enzymes immobilized on these materials, the development of enzyme-based bioreactors, and prospects for these biocatalysts. In summary, this review provides a concise comparison of the use of magnetic nanomaterials for enzyme stabilization, highlighting potential industrial applications and contributing to manufacturing optimization.

Scientometric analysis of electrocatalysis in wastewater treatment: today and tomorrow

Electrocatalytic methods are valuable tools for addressing water pollution and scarcity, offering effective pollutant removal and resource recovery. To investigate the current status and future trends of electrocatalysis in wastewater treatment, a detailed analysis of 9417 papers and 4061 patents was conducted using scientometric methods. China emerged as the leading contributor to publications, and collaborations between China and the USA have emerged as the most frequent partnerships. Primary article co-citation clusters focused on oxygen evolution reaction and electrochemical oxidation, transitioning towards advanced oxidation processes ("persulfate activation"), and electrocatalytic reduction processes ("nitrate reduction"). Bifunctional catalysts, theoretical calculations, electrocatalytic combination technologies, and emerging contaminants were identified as current research hotspots. Patent analysis revealed seven types of electrochemical technologies, which were compared using SWOT analysis, highlighting electrochemical oxidation as prominent. The technological evolution presented the pathway of electro-Fenton to combined electrocatalytic technologies with biochemical processes, and finally to coupling with electrocoagulation. Standardized evaluation systems, waste resource utilization, and energy conservation were important directions of innovation in electrocatalytic technologies. Overall, this study provided a reference for researchers to understand the framework of electrocatalysis in wastewater treatment and also shed light on potential avenues for further innovation in the field.

A review on recent environmental electrochemistry approaches for the consolidation of a circular economy model

Availability of raw materials in the chemical industry is related to the selection of the chemical processes in which they are used as well as to the efficiency, cost, and eventual evolution to more competitive dynamics of transformation technologies. In general terms however, any chemically transforming technology starts with the extraction, purification, design, manufacture, use, and disposal of materials. It is important to create a new paradigm towards green chemistry, sustainability, and circular economy in the chemical sciences that help to better employ, reuse, and recycle the materials used in every aspect of modern life. Electrochemistry is a growing field of knowledge that can help with these issues to reduce solid waste and the impact of chemical processes on the environment. Several electrochemical studies in the last decades have benefited the recovery of important chemical compounds and elements through electrodeposition, electrowinning, electrocoagulation, electrodialysis, and other processes. The use of living organisms and microorganisms using an electrochemical perspective (known as bioelectrochemistry), is also calling attention to "mining", through plants and microorganisms, essential chemical elements. New process design or the optimization of the current technologies is a major necessity to enhance production and minimize the use of raw materials along with less generation of wastes and secondary by-products. In this context, this contribution aims to show an up-to-date scenario of both environmental electrochemical and bioelectrochemical processes for the extraction, use, recovery and recycling of materials in a circular economy model.