Biological stability of drinking water refers to the concept of providing consumers with drinking water of same microbial quality at the tap as produced at the water treatment facility. However, uncontrolled growth of bacteria can occur during distribution in water mains and premise plumbing, and can lead to hygienic (e.g., development of opportunistic pathogens), aesthetic (e.g., deterioration of taste, odor, color) or operational (e.g., fouling or biocorrosion of pipes) problems. Drinking water contains diverse microorganisms competing for limited available nutrients for growth. Bacterial growth and interactions are regulated by factors, such as (i) type and concentration of available organic and inorganic nutrients, (ii) type and concentration of residual disinfectant, (iii) presence of predators, such as protozoa and invertebrates, (iv) environmental conditions, such as water temperature, and (v) spatial location of microorganisms (bulk water, sediment, or biofilm). Water treatment and distribution conditions in water mains and premise plumbing affect each of these factors and shape bacterial community characteristics (abundance, composition, viability) in distribution systems. Improved understanding of bacterial interactions in distribution systems and of environmental conditions impact is needed for better control of bacterial communities during drinking water production and distribution. This article reviews (i) existing knowledge on biological stability controlling factors and (ii) how these factors are affected by drinking water production and distribution conditions. In addition, (iii) the concept of biological stability is discussed in light of experience with well-established and new analytical methods, enabling high throughput analysis and in-depth characterization of bacterial communities in drinking water. We discussed, how knowledge gained from novel techniques will improve design and monitoring of water treatment and distribution systems in order to maintain good drinking water microbial quality up to consumer’s tap. A new definition and methodological approach for biological stability is proposed.

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Biological Stability of Drinking Water: Controlling Factors, Methods, and Challenges

Monitoring microbiological changes in drinking water systems using a fast and reproducible flow cytometric method.

https://cyberleninka.org/article/n/1048098.pdf

Flow cytometry for the development of biotechnological processes with microalgae.

Dynamic control of gene expression can have far-reaching implications for biotechnological applications and biological discovery. Thanks to the advantages of light, optogenetics has emerged as an ideal technology for this task. Current state-of-the-art methods for optical expression control fail to combine precision with repeatability and cannot withstand changing operating culture conditions. Here, we present a novel fully automatic experimental platform for the robust and precise long-term optogenetic regulation of protein production in liquid Escherichia coli cultures. Using a computer-controlled light-responsive two-component system, we accurately track prescribed dynamic green fluorescent protein expression profiles through the application of feedback control, and show that the system adapts to global perturbations such as nutrient and temperature changes. We demonstrate the efficacy and potential utility of our approach by placing a key metabolic enzyme under optogenetic control, thus enabling dynamic regulation of the culture growth rate with potential applications in bacterial physiology studies and biotechnology.

/pdf/automated-optogenetic-feedback-control-for-precise-and-49eny4diuq.pdf

Automated optogenetic feedback control for precise and robust regulation of gene expression and cell growth

Potential impacts of changing supply-water quality on drinking water distribution: A review

Accurate and sensitive online detection tools would benefit both fundamental research and practical applications in aquatic microbiology. Here, we describe the development and testing of an online flow cytometer (FCM), with a specific use foreseen in the field of drinking water microbiology. The system incorporated fully automated sampling and fluorescent labeling of bacterial nucleic acids with analysis at 5-min intervals for periods in excess of 24 h. The laboratory scale testing showed sensitive detection (< 5% error) of bacteria over a broad concentration range (1 × 10(3) -1 × 10(6) cells mL(-1) ) and particularly the ability to track both gradual changes and dramatic events in water samples. The system was tested with bacterial pure cultures as well as indigenous microbial communities from natural water samples. Moreover, we demonstrated the possibility of using either a single fluorescent dye (e.g., SYBR Green I) or a combination of two dyes (SYBR Green I and Propidium Iodide), thus broadening the application possibilities of the system. The online FCM approach described herein has considerable potential for routine and continuous monitoring of drinking water, optimization of specific drinking water processes such as biofiltration or disinfection, as well as aquatic microbiology research in general.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/cyto.a.22048

Development and laboratory-scale testing of a fully automated online flow cytometer for drinking water analysis.

Real-time on-line flow cytometry for bioprocess monitoring.

Controlled fed-batch by tracking the maximal culture capacity.

The state-of-routine monitoring items established in the bioprocess industry as well as some important state-of-the-art methods are briefly described and the potential pitfalls discussed. Among those are physical and chemical variables such as temperature, pressure, weight, volume, mass and volumetric flow rates, pH, redox potential, gas partial pressures in the liquid and molar fractions in the gas phase, infrared spectral analysis of the liquid phase, and calorimetry over an entire reactor. Classical as well as new optical versions are addressed. Biomass and bio-activity monitoring (as opposed to "measurement") via turbidity, permittivity, in situ microscopy, and fluorescence are critically analyzed. Some new(er) instrumental analytical tools, interfaced to bioprocesses, are explained. Among those are chromatographic methods, mass spectrometry, flow and sequential injection analyses, field flow fractionation, capillary electrophoresis, and flow cytometry. This chapter surveys the principles of monitoring rather than compiling instruments.

Bernhard Sonnleitner

Papers

Development and laboratory-scale testing of a fully automated online flow cytometer for drinking water analysis.

Real-time on-line flow cytometry for bioprocess monitoring.

Controlled fed-batch by tracking the maximal culture capacity.

Automated measurement and monitoring of bioprocesses: key elements of the M(3)C strategy.

Real‐Time Measurement and Monitoring of Bioprocesses