Propionate outperforms conventional acetate as electron donors for highly-sensitive electrochemical active biofilm sensors in water biotoxicity early-warning.

With the ability to generate in situ real-time electric signals, electrochemically active biofilm (EAB) sensors have attracted wide attention as a promising water biotoxicity early-warning device. Organic matters serving as the electron donors potentially affect the electric signal's output and the sensitivity of the EAB sensor. To explore the influence of organic matters on EAB sensor's performance, this study tested six different organic matters during the sensor's inoculation. Besides the acetate, a conventional and widely used organic matter, propionate and lactate were also found capable of starting up the sensor. Moreover, the propionate-fed (PF) sensor delivered the highest sensitivity, which are respectively 1.4 times and 2.8 times of acetate-fed (AF) sensor and lactate-fed (LF) sensor. Further analysis revealed that EAB of PF sensor had more vulnerable intracellular metabolism than the others, which manifested as the most severe energy metabolic suppression and reactive oxygen species attack. Regarding the microbial function, a two-component system that was deemed as an environment awareness system was found in the EAB of PF, which also contributed to its high sensitivity. Finally, PF sensor was tested in real water environment to deliver early-warning signals.

Bacillus sp. alone or combined with salicylic acid inhibited Trichoderma spp. infection on harvested white Hypsizygus marmoreus.

Introduction: White Hypsizygus marmoreus is a popular edible mushroom. It is rich in nutrition and flavor but vulnerable to fungal disease, resulting in nutrient loss and aging. Methods: In this study, the pathogenic fungus Trichoderma spp. BBP-6 and its antagonist Bacillus sp. 1-23 were isolated and identified. The negative effects caused by this pathogen were judged by detecting a series of changes in the infected white H. marmoreus. The effects of Bacillus sp. 1-23 on Trichoderma spp. BBP-6 and the infected white H. marmoreus were detected. The effect of Bacillus sp. 1-23 treatment combined with salicylic acid (SA) was also considered. Results: The results showed that Trichoderma spp. BBP-6 could affect the activities of antioxidant enzymes PAL, POD, CAT, SOD, GR, PPO, and APX to interfere with the stability of the white H. marmoreus antioxidant enzyme system and cause the mushroom severe browning and nutrition loss, as well as general quality deterioration. Bacillus sp. 1-23 could produce chitinase and chitosanase enzymes to inhibit Trichoderma spp. BBP-6 directly. SA reinforced this inhibitory. Bacillus sp. 1-23 alone or combined with SA could help white H. marmoreus from the Trichoderma spp. BBP-6 infection to effectively maintain nutrients, restore and stabilize the antioxidant system, and reduce the production of malondialdehyde, superoxide anion and hydrogen peroxide. Discussion: Thus, such treatments could be considered potential methods to alleviate damage from disease and extend the shelf life of white H. marmoreus.

Whole-cell biophotovoltaic systems for renewable energy generation: A systematic analysis of existing knowledge.

The development of carbon-neutral fuel sources is an essential step in addressing the global fossil energy crisis. Whole-cell biophotovoltaic systems (BPVs) are a renewable, non-polluting energy-generating device that utilizes oxygenic photosynthetic microbes (OPMs) to split water molecules and generate bioelectricity under the driving of light energy. Since 2006, BPVs have been widely studied, with the order magnitudes of power density increasing from 10-4 mW/m2 to 103 mW/m2. This review examines the extracellular electron transfer (EET) mechanisms and regulation techniques of BPVs from biofilm to external environment. It is found that the EET of OPMs is mainly mediated by membrane proteins, with terminal oxidase limiting the power output. Synechocystis sp. PCC6803 and Chlorella vulgaris are two species that produce high power density in BPVs. The use of metal nanoparticles mixing, 3D pillar array electrodes, microfluidic technology, and transient-state operation models can significantly enhance power density. Challenges and potential research directions are discussed, including a deeper analysis of EET mechanisms and dynamics, the development of modular devices, integration of multiple regulatory components, and the exploration of novel BPV technologies.

Titanium mesh as the anode of electrochemically active biofilm sensor for improved sensitivity in water toxicity real-time early-warning.

As serious water ecological pollution caused by toxicant leakage occurs frequently, early-warning for toxicity presented in water environment attracts increasing attentions as it saves time to retain water safety and human health. Electrochemically active biofilm (EAB) sensor is a promising device for in situ real-time water toxicity early-warning. To improve the sensitivity of EAB sensor particularly for low-concentration toxicity warning, this study employed titanium mesh (TiM) as the anode to construct an EAB sensor. Compared to traditional EAB sensor with carbon felt (CF) anode, the sensitivity of the TiM sensor was increased up to 37.4 times. The effects of mesh size (TiM50, TiM100, TiM150) and operation mode (flow-by and flow-through) on the sensitivity of TiM sensors were further investigated. Results showed the sensor with TiM100 anode had the highest inhibition rate (IR) in flow-by mode, attributed to low charge transfer resistance (Rct) and fast mass transfer. Flow-through operation could further enhance TiM100 sensor's sensitivity from flow-by operation and succeeded to signal as low as 0.0025% formaldehyde, the lowest so far tested in EAB sensor with sensing anode. Multiple toxicity shocks on flow-through TiM100 sensor revealed its good recoverability towards all tested formaldehyde concentration from 0.01% to 0.0025%, during which electrochemical activity degradation and biomass accumulation partially impaired the repeatability. This work highlights the great improvement of EAB sensors by utilizing titanium mesh as EAB carrier and provides a reference for the practical application of metallic materials for EAB sensors.

Extracellular electron transfer and the conductivity in microbial aggregates during biochemical wastewater treatment: A bottom-up analysis of existing knowledge.

Microbial extracellular electron transfer (EET) plays a crucial role in bioenergy production and resource recovery from wastewater. Interdisciplinary efforts have been made to unveil EET processes at various spatial scales, from nanowires to microbial aggregates. Electrical conductivity has been frequently measured as an indicator of EET efficiency. In this review, the conductivity of nanowires, biofilms, and granular sludge was summarized, and factors including subjects, measurement methods, and conducting conditions that affect the conductivity difference were discussed in detail. The high conductivity of nanowires does not necessarily result in efficient EET in microbial aggregates due to the existence of non-conductive substances and contact resistance. Improving the conductivity measurement of microbial aggregates is important because it enables the calculation of an EET flux from conductivity and a comparison of the flux with mass transfer coefficients. This review provides new insight into the significance, characterization, and optimization of EET in microbial aggregates during a wastewater treatment process.

l-Cysteine Treatment Delayed the Quality Deterioration of Fresh-Cut Button Mushrooms by Regulating Oxygen Metabolism, Inhibiting Water Loss, and Stimulating Endogenous H2S Production.

Although fresh-cut button mushrooms are popular with consumers, quality deterioration presents a significant shelf-life challenge. In this study, fresh-cut button mushrooms were treated with 0.25 g/L l-cysteine (l-Cys) and evaluated in terms of quality, physiology, and transcriptome sequencing. The results indicated that l-Cys application significantly delayed the browning degree of fresh-cut button mushrooms and reduced weight loss. l-Cys treatment reduced the malondialdehyde content, lipoxygenase activity, and reducing sugar levels while enhancing the soluble protein and total phenolic content. Furthermore, l-Cys treatment reduced the O2- generation rate and H2O2 accumulation while enhancing the catalase activity. Moreover, l-Cys improved the superoxide dismutase, glutathione reductase, and phenylalanine ammonia-lyase activities while reducing those of polyphenol oxidase and peroxidase. Additionally, l-Cys treatment increased endogenous H2S production and AbCBS enzyme activity while decreasing AbCSE enzyme activity. Notably, additional treatment with 1 mM propargylglycine significantly reduced the effect of l-Cys. Moreover, transcriptome sequencing analysis indicated that the differentially expressed genes in the l-Cys group were primarily related to the reactive oxygen species metabolism, oxidoreductase process, membrane integrality, and sulfur metabolism. These findings suggested that l-Cys treatment delayed the aging and extended the shelf life of fresh-cut button mushrooms by regulating the active oxygen species metabolism and water loss and stimulating endogenous H2S production.