Automatic biodetector of water toxicity (ABTOW) as a tool for examination of phenol and cyanide contaminated water

Decomposition of non-steroidal anti-inflammatory drugs by activated sludge supported by biopreparation in sequencing batch reactor

The presence of non-steroidal anti-inflammatory drugs in wastewater from sewage treatment plants indicates that they are not completely biodegradable. The designed biopreparation based on immobilized bacteria enables the degradation of paracetamol, ibuprofen, naproxen and diclofenac at a rate of 0.50 mg/L*day, 0.14 mg/L*day, 0.16 mg/L*day and 0.04 mg/L*day, respectively. Lower degradation of drugs in the mixture than in monosubstrate systems indicates their additive, antagonistic effect, limiting the degradative capacity of microorganisms. The biopreparation is stable for at least 6 weeks in bioreactor conditions. Biochemical parameters of activated sludge functioning showed increased oxygen demand, which was related to increased ammonia concentration caused by long-term exposure of activated sludge to drugs. Reduced metabolic activity was also observed. The preparation enables decomposing drugs and their metabolites, restoring the activated sludge's functionality. The tested biopreparation can support activated sludge in sewage treatment plants in degrading non-steroidal anti-inflammatory drugs and phenolic compounds.

Modeling of Nitrification Kinetics in a Respirometric Biosensor under Suboptimal Conditions

Sensitive detection with cell biosensors requires optimization of their working conditions and standardization of the response in variable physicochemical conditions. The introduction of an analyte to a sensor, which contributes to this variability, may account for the modeling of microbial metabolism. We constructed a multiparameter model of a water toxicity sensor of Automatic Biodetector for Water Toxicity (ABTOW), developed by our group and based on nitrifying bacteria. The model describes the kinetics of nitrification as a function of four orthogonal parameters: temperature, pH, oxygen and ammonium concentration. Furthermore, we characterized the signal-to-noise ratio (SNR) of the ABTOW readout as a function of these parameters. Thus, a region of parameter space corresponding to optimal ABTOW operation is identified and its sensitivity quantified. We applied the model to describe the ABTOW performance in non-equilibrium conditions produced by rapid changes in pH and temperature. In sum, the model based on four physicochemical parameters describes changes in the biosensor’s activity, the biological element of which are nitrifying bacteria characterized by simple chemolithoautotrophic metabolism. The description of reaction kinetics through multiparameter modeling in combination with stability analysis can find application in process control in biotechnology, biodetection and environmental research.

The Use of Electroactive Halophilic Bacteria for Improvements and Advancements in Environmental High Saline Biosensing

Halophilic bacteria are remarkable organisms that have evolved strategies to survive in high saline concentrations. These bacteria offer many advances for microbial-based biotechnologies and are commonly used for industrial processes such as compatible solute synthesis, biofuel production, and other microbial processes that occur in high saline environments. Using halophilic bacteria in electrochemical systems offers enhanced stability and applications in extreme environments where common electroactive microorganisms would not survive. Incorporating halophilic bacteria into microbial fuel cells has become of particular interest for renewable energy generation and self-powered biosensing since many wastewaters can contain fluctuating and high saline concentrations. In this perspective, we highlight the evolutionary mechanisms of halophilic microorganisms, review their application in microbial electrochemical sensing, and offer future perspectives and directions in using halophilic electroactive microorganisms for high saline biosensing.

Flat microliter membrane-based microbial fuel cell as "on-line sticker sensor" for self-supported in situ monitoring of wastewater shocks

Novel flat membrane-based microbial fuel cell (MMFC) sensors were developed by compacting two filter membranes coated with carbon ink. High micro-porosity and hydrophilicity of membranes offered the distinct advantages of short acclimation period (couple hours), simple compact configuration with microliter size, and high sensitivity and stability. MMFC sensors were examined at two toxic shocks (chromium and nickel) in a batch-mode test chamber, and rapidly responded to shock types and concentrations. The variation of voltage output was correlated with open circuit potential (OCP). Filter membranes facilitated bacterial attachment and shortened acclimation. The MMFC sensors showed good reusability and recovered several days after toxic shocks. The robustness of MMFC sensors was validated through 1-month tests. The stability of sensor signals was examined with coefficient of variance (CV) statistical analysis. The flat microliter MMFC has a great potential as "on-line sticker sensor" for real time in situ monitoring of wastewater quality.

Biological early warning system based on the responses of aquatic organisms to disturbances: a review

Aquatic ecosystems are subject to a number of anthropogenic disturbances, including environmental toxicants. The efficient monitoring of water resources is fundamental for effective management of water quality and aquatic ecosystems. Spot sampling and continuous water quality monitoring based on physicochemical factors are conducted to assess water quality. However, not all contaminants or synergistic and antagonistic toxic effects can be determined by solely analyzing the physicochemical factors. Thus, various biotests have been developed using long-term and automatic observation studies based on the ability of the aquatic organisms to continuously sense a wide range of pollutants. In addition, a biological early warning system (BEWS) has been developed based on the response behaviors of organisms to continuously detect a wide range of pollutants for effective water quality monitoring and management. However, large amounts of data exhibiting non-linearity and individual behavioral variation are continuously accumulated over long-term and continuous behavioral monitoring studies. Thus, appropriate mathematical and computational data analyses are necessary to manage and interpret such large datasets. Here, we review the development and application of BEWS by using various groups of organisms and the computational methods used to process the behavioral monitoring data.

Long term assessment of factors affecting nitrifying bacteria communities and N-removal in a full-scale biological process treating high strength hazardous wastewater

Over a 3 year period, interactions between nitrifying bacterial communities and the operational parameters of a full-scale wastewater treatment plant were analyzed to assess their impact on nitrification performance. Throughout the study period, nitrification fluctuated while Nitrosomonas europaea and Nitrosomonas nitrosa, the two major ammonia oxidizing bacteria (AOB) communities, showed resistance to changes in operational and environmental conditions. Nitrobacter populations mostly exceeded those of Nitrospira within nitrite oxidizing bacteria (NOB). Meanwhile, principal component analysis (PCA) results revealed that a close association between Nitrobacter and nitrite concentration as well as a direct correlation between the quantity of AOB and influent SCN- concentration. The serial shifts of data points over time showed that the nitrification of a full-scale treatment plant has been gradually suppressed by the influence of influent COD and phenol concentrations.

Stimulatory effect of xenobiotics on oxidative electron transport of chemolithotrophic nitrifying bacteria used as biosensing element

Electron transport chain (ETCh) of ammonium (AOB) and nitrite oxidizing bacteria (NOB) participates in oxidation of ammonium to nitrate (nitrification). Operation of ETCh may be perturbed by a range of water-soluble xenobiotics. Therefore, consortia of nitrifying bacteria may be used as a biosensor to detect water contamination. A surprising feature of this system is an increase of oxygen consumption, detected in the presence of certain inhibitors of ETCh. Thus, to shed light on the mechanism of this effect (and other differences between inhibitors) we monitored separately respiration of the bacteria of the first (AOB - Nitrosomonas) and second (NOB -Nitrobacter) stages of nitrification. Furthermore, we measured plasma membrane potential and the level of reduction of NAD(P)H. We propose a novel model of ETCh in NOB to explain the role of reverse electron transport in the stimulation of oxygen consumption (previously attributed to hormesis).