A photosynthetic toxicity biosensor for water

A Review of Advanced Sensor Technologies for Aquatic Products Freshness Assessment in Cold Chain Logistics

The evaluation of the upkeep and freshness of aquatic products within the cold chain is crucial due to their perishable nature, which can significantly impact both quality and safety. Conventional methods for assessing freshness in the cold chain have inherent limitations regarding specificity and accuracy, often requiring substantial time and effort. Recently, advanced sensor technologies have been developed for freshness assessment, enabling real-time and non-invasive monitoring via the detection of volatile organic compounds, biochemical markers, and physical properties. The integration of sensor technologies into cold chain logistics enhances the ability to maintain the quality and safety of aquatic products. This review examines the advancements made in multifunctional sensor devices for the freshness assessment of aquatic products in cold chain logistics, as well as the application of pattern recognition algorithms for identification and classification. It begins by outlining the categories of freshness criteria, followed by an exploration of the development of four key sensor devices: electronic noses, electronic tongues, biosensors, and flexible sensors. Furthermore, the review discusses the implementation of advanced pattern recognition algorithms in sensor devices for freshness detection and evaluation. It highlights the current status and future potential of sensor technologies for aquatic products within the cold chain, while also addressing the significant challenges that remain to be overcome.

Evaluating application of photosynthetic microbial fuel cell to exhibit efficient carbon sequestration with concomitant value-added product recovery from wastewater: A review

The emission of CO2 from industrial (24%) and different anthropogenic activities, like transportation (27%), electricity production (25%), and agriculture (11%), can lead to global warming, which in the long term can trigger substantial climate changes. In this regard, CO2 sequestration and wastewater treatment in tandem with bioenergy production through photosynthetic microbial fuel cell (PMFC) is an economical and sustainable intervention to address the problem of global warming and elevating energy demands. Therefore, this review focuses on the application of different PMFC as a bio-refinery approach to produce biofuels and power generation accompanied with the holistic treatment of wastewater. Moreover, CO2 bio-fixation and electron transfer mechanism of different photosynthetic microbiota, and factors affecting the performance of PMFC with technical feasibility and drawbacks are also elucidated in this review. Also, low-cost approaches such as utilization of bio-membrane like coconut shell, microbial growth enhancement by extracellular cell signalling mechanisms, and exploitation of genetically engineered strain towards the commercialization of PMFC are highlighted. Thus, the present review intends to guide the budding researchers in developing more cost-effective and sustainable PMFCs, which could lead towards the commercialization of this inventive technology.

Microbial Fuel Cell Biosensor with Capillary Carbon Source Delivery for Real-Time Toxicity Detection

A microbial fuel cell (MFC) biosensor with an anode as a sensing element is often unreliable at low or significantly fluctuating organic matter concentrations. To remove this limitation, this work demonstrates capillary action-aided carbon source delivery to an anode-sensing MFC biosensor for use in carbon-depleted environments, e.g., potable water. First, different carbon source delivery configurations using several thread types, silk, nylon, cotton, and polyester, are evaluated. Silk thread was determined to be the most suitable material for passive delivery of a 40 g L-1 acetate solution. This carbon source delivery system was then incorporated into the design of an MFC biosensor for real-time detection of toxicity spikes in tap water, providing an organic matter concentration of 56 ± 15 mg L-1. The biosensor was subsequently able to detect spikes of toxicants such as chlorine, formaldehyde, mercury, and cyanobacterial microcystins. The 16S sequencing results demonstrated the proliferation of Desulfatirhabdium (10.7% of the total population), Pelobacter (10.3%), and Geobacter (10.2%) genera. Overall, this work shows that the proposed approach can be used to achieve real-time toxicant detection by MFC biosensors in carbon-depleted environments.

Life in biophotovoltaics systems

As the most suitable potential clean energy power generation technology, biophotovoltaics (BPV) not only inherits the advantages of traditional photovoltaics, such as safety, reliability and no noise, but also solves the disadvantages of high pollution and high energy consumption in the manufacturing process, providing new functions of self-repair and natural degradation. The basic idea of BPV is to collect light energy and generate electric energy by using photosynthetic autotrophs or their parts, and the core is how these biological materials can quickly and low-loss transfer electrons to the anode through mediators after absorbing light energy and generating electrons. In this mini-review, we summarized the biological materials widely used in BPV at present, mainly cyanobacteria, green algae, biological combinations (using multiple microorganisms in the same BPV system) and isolated products (purified thylakoids, chloroplasts, photosystem I, photosystem II), introduced how researchers overcome the shortcomings of low photocurrent output of BPV, pointed out the limitations that affected the development of BPV' biological materials, and put forward reasonable assumptions accordingly.

The use of marine microalgae in microbial fuel cells, photosynthetic microbial fuel cells and biophotovoltaic platforms for bioelectricity generation

Algal green energy has emerged as an alternative to conventional energy production using fossil fuels. Microbial fuel cells (MFCs), photosynthetic microbial fuel cells (PMFCs) and biophotovoltaic (BPV) platforms have been developed to utilize microalgae for bioelectricity generation, wastewater treatment and biomass production. There remains a lack of research on marine microalgae in these systems, so to the best of our knowledge, all information on their integration in these systems have been gathered in this review, and are used to compare with the interesting studies on freshwater microalgae. The performance of the systems is extremely reliant on the microalgae species and/or microbial community used, the size of the bio-electrochemical cell, and electrode material and distance used. The mean was calculated for each system, PMFC has the highest average maximum power density of 344 mW/m², followed by MFC (179 mW/m²) and BPV (58.9 mW/m²). In addition, the advantages and disadvantages of each system are highlighted. Although all three systems face the issue of low power outputs, the integration of a suitable energy harvester could potentially increase power efficiency and make them applicable for lower power applications.

Long-term in situ bioelectrochemical monitoring of biohythane process: Metabolic interactions and microbial evolution

Microbial stability and evolution are a critical aspect for biosensors, especially in detecting dynamic and emerging anaerobic biohythane production. In this study, two upflow air-cathode chamber microbial fuel cells (UMFCs) were developed for in situ monitoring of the biohydrogen and biomethane reactors under a COD range of 1000-6000 mg/L and 150-1000 mg/L, respectively. Illumina MiSeq sequencing evidenced the dramatic shift of dominant microbial communities in UMFCs from hydrolytic and acidification bacteria (Clostridiaceae_1, Ruminococcaceae, Peptostreptococcaceae) to acetate-oxidizing bacteria (Synergistaceae, Dysgonomonadaceae, Spirochaetaceae). In addition, exoelectroactive bacteria evaluated from Enterobacteriaceae and Burkholderiaceae to Desulfovibrionaceae and Propionibacteriaceae. Especially, Hydrogenotrophic methanogens (Methanobacteriaceae) were abundant at 93.41% in UMFC (for monitoring hydrogen reactor), which was speculated to be a major metabolic pathway for methane production. Principal component analysis revealed a similarity in microbial structure between UMFCs and methane bioreactors. Microbial network analysis suggested a more stable community structure of UMFCs with 205 days' operation.

Advancing the fundamental understanding and practical applications of photo-bioelectrocatalysis

Photo-bioelectrocatalysis combines the natural and highly sophisticated process of photosynthesis in biological entities with an abiotic electrode surface, to perform semi-artificial photosynthesis. However, challenges must be overcome, from the establishment and understanding of the photoexcited electron harvesting process at the electrode to the electrochemical characterization of these biotic/abiotic systems, and their subsequent tuning for enhancing energy generation (chemical and/or electrical). This Feature Article discusses the various approaches utilized to tackle these challenges, particularly focusing on powerful multi-disciplinary approaches for understanding and improving photo-bioelectrocatalysis. Among them is the combination of experimental evidence and quantum mechanical calculations, the use of bioinformatics to understand photo-bioelectrocatalysis at a metabolic level, or bioengineering to improve and facilitate photo-bioelectrocatalysis. Key aspects for the future development of photo-bioelectrocatalysis are presented alongside future research needs and promising applications of semi-artificial photosynthesis.

Portable, Disposable, Paper-Based Microbial Fuel Cell Sensor Utilizing Freeze-Dried Bacteria for In Situ Water Quality Monitoring

Water quality monitoring is becoming an essential part of our lives as increasing human activities continue to spill unknown and unexpected contaminants into our water systems. To ensure the provision of safe and clean water to the public and the ecosystem, the development of rapid and sensitive in situ early warning systems for water toxicity monitoring is crucial. In this work, an entirely paper-based microbial fuel cell sensor utilizing freeze-dried bacteria is demonstrated as a portable and disposable water toxicity sensor. The bacterial cells were preinoculated on the anode reservoir of the device, and they were freeze-dried, making their on-site and on-demand applications possible. Upon rehydration of the bacteria with the water samples, current readings were obtained, and inhibition ratios (IRs) were calculated for different concentrations of formaldehyde as a model toxin. For 0.001, 0.01, and 0.02% of formaldehyde, IRs of 7.88, 16.08, and 23.14% were obtained, respectively. These IRs showed a very good linearity with the formaldehyde concentrations at R ² = 0.995. Additionally, the shelf life of the freeze-dried microbial fuel cell sensor was investigated. Even after 14 days of storage in the desiccator, at 4, and at -20 °C, the performance outputs compared to the new device were all at 96%.

Purple Bacteria and 3D Redox Hydrogels for Bioinspired Photo-bioelectrocatalysis

A major challenge for the implementation of intact bacterial cells in photo-bioelectrochemical systems remains the hindered extracellular electron transfer. This study focuses on purple bacteria, photosynthetic microorganisms particularly interesting for the development of bioelectrochemical systems because of their versatile metabolisms. Although soluble monomeric redox mediators have been proven as effective systems for electron transfer mediation, their application in the field is not preferable owing to their toxicity and unwanted release into the environment. An abiotic/biotic photoanode is reported in which a bioinspired redox mediating system is implemented in a 3D geometry allowing to "electrically wire" intact bacterial cells. The 3D photoanode decreased the overpotential required for harvesting photoexcited electrons, operating at +0.073 V versus the saturated calomel electrode (SCE). Accordingly, the overpotential was significantly reduced compared with a pioneering Os-redox polymer reported in literature, which required operation at +0.303 V versus SCE. These results provide the basis for further development of bio-photoanodes for light-powered biosensing and power generation.

Purple bacteria photo-bioelectrochemistry: enthralling challenges and opportunities

Perspective of research directions exploring purple bacteria photo-bioelectrochemistry: from harvesting photoexcited electrons to bioelectrochemical systems development.

A Portable, Single-Use, Paper-Based Microbial Fuel Cell Sensor for Rapid, On-Site Water Quality Monitoring

Human access to safe water has become a major problem in many parts of the world as increasing human activities continue to spill contaminants into our water systems. To guarantee the protection of the public as well as the environment, a rapid and sensitive way to detect contaminants is required. In this work, a paper-based microbial fuel cell was developed to act as a portable, single-use, on-site water quality sensor. The sensor was fabricated by combining two layers of paper for a simple, low-cost, and disposable design. To facilitate the use of the sensor for on-site applications, the bacterial cells were pre-inoculated onto the device by air-drying. To eliminate any variations, the voltage generated by the microorganism before and after the air-drying process was measured and calculated as an inhibition ratio. Upon the addition of different formaldehyde concentrations (0%, 0.001%, 0.005%, and 0.02%), the inhibition ratios obtained were 5.9 ± 0.7%, 6.9 ± 0.7%, 8.2 ± 0.6%, and 10.6 ± 0.2%, respectively. The inhibition ratio showed a good linearity with the formaldehyde concentrations at R² = 0.931. Our new sensor holds great promise in monitoring water quality as a portable, low-cost, and on-site sensor.

A Storable Mediatorless Electrochemical Biosensor for Herbicide Detection

A novel mediatorless photo-bioelectrochemical sensor operated with a biofilm of the cyanobacterium Synechocystis PCC6803 wt. for herbicide detection with long term stability (>20 days) was successfully developed and tested. Photoanodic current generation was obtained in the absence of artificial mediators. The inhibitory effect on photocurrent of three commonly used herbicides (i.e., atrazine, diuron, and paraquat) was used as a means of measuring their concentrations in aqueous solution. The injection of atrazine and diuron into the algal medium caused an immediate photocurrent drop due to the inhibition of photosynthetic electron transport. The detected concentrations were suitable for environmental analysis, as revealed by a comparison with the freshwater quality benchmarks set by the Environmental Protection Agency of the United States (US EPA). In contrast, paraquat caused an initial increase (~2 h) of the photocurrent effect of about 200%, as this compound can act as a redox mediator between the cells and the anode. A relatively long-term stability of the biosensor was demonstrated, by keeping anodes colonized with cyanobacterial biofilm in the dark at 4 °C. After 22 days of storage, the performance in terms of the photocurrent was comparable with the freshly prepared biosensor. This result was confirmed by the measurement of chlorophyll content, which demonstrated preservation of the cyanobacterial biofilm. The capacity of this biosensor to recover after a cold season or other prolonged environmental stresses could be a key advantage in field applications, such as in water bodies and agriculture. This study is a step forward in the biotechnological development and implementation of storable mediatorless electrochemical biosensors for herbicide detection.

Biotechnological Advances in the Design of Algae-Based Biosensors

In addition to their use in biomass production and bioremediation, algae have been extensively exploited in biosensing applications. Algae-based biosensors have demonstrated potential for sensitive, sustainable, and multiplexed detection of analytes of agroenvironmental and security interest. Their advantages include the availability of different algal bioreceptors including whole cells and their photosynthetic subcomponents, their potential to be integrated into dual transduction miniaturized devices, and the opportunity for continuous environmental monitoring. Despite obstacles including limited stability and selectivity, algae-based biosensing is a realistic prospect that has some recent effective applications. Strategic exploitation of cutting-edge technologies including materials science, nanotechnology, microfluidics, and genome editing will help to achieve the full potential of algae-based sensors.

The Development of Biophotovoltaic Systems for Power Generation and Biological Analysis

Biophotovoltaic systems (BPVs) resemble microbial fuel cells, but utilise oxygenic photosynthetic microorganisms associated with an anode to generate an extracellular electrical current, which is stimulated by illumination. Study and exploitation of BPVs have come a long way over the last few decades, having benefited from several generations of electrode development and improvements in wiring schemes. Power densities of up to 0.5 W m-2 and the powering of small electrical devices such as a digital clock have been reported. Improvements in standardisation have meant that this biophotoelectrochemical phenomenon can be further exploited to address biological questions relating to the organisms. Here, we aim to provide both biologists and electrochemists with a review of the progress of BPV development with a focus on biological materials, electrode design and interfacial wiring considerations, and propose steps for driving the field forward.