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The development of a standardized, generic method for concentrating suspensions in continuous flow is challenging. In this study, we developed and tested a device capable of concentrating suspensions with an already high cell concentration to meet diverse industrial requirements. To address typical multitasking needs, we concentrated suspensions with high solid content under a variety of conditions. Cells from Saccharomyces cerevisiae, Escherichia coli, and Chinese hamster ovary cells were effectively focused in the center of the main channel of a microfluidic device using acoustophoresis. The main channel bifurcates into three outlets, allowing cells to exit through the central outlet, while the liquid evenly exits through all outlets. Consequently, the treatment separates cells from two-thirds of the surrounding liquid. We investigated the complex interactions between parameters. Increasing the channel depth results in a decrease in process efficiency, attributed to a decline in acoustic energy density. The study also revealed that different cell strains exhibit distinct acoustic contrast factors, originating from differences in dimensions, compressibility, and density values. Finally, a combination of high solid content and flow rate leads to an increase in diffusion through a phenomenon known as shear-induced diffusion. Key points: • Acoustic focusing in a microchannel was used to concentrate cell suspensions • The parameters influencing focusing at high concentrations were studied • Three different cell strains were successfully concentrated [ABSTRACT FROM AUTHOR]

This study focuses on evaluating the effectiveness of various cell concentrations of bacillus bacteria in mending cracks within recycled concrete containing coarse aggregates. In this investigation, the introduction of bacillus bacterial sustainable concrete as a solution for addressing crack repairs. This innovative concrete formulation not only provides environmentally friendly alternatives but also offers economic benefits. This research involves the incorporation of coarse aggregates into the concrete mix, along with the partial substitution of cement by Fly ash and Ground Granulated Blast Furnace Slag (GGBS), each accounting for 20% of the mix. The coarse aggregates consist of Recycled Concrete Aggregate (RCA) in varying proportions: 0%, 50%, and 100%. Additionally, Bacillus licheniformis was used at concentrations of 10³, 105, and 107 cells/mL, respectively. The findings indicate a positive correlation between the healing percentage of cracks, as measured by Ultrasonic Pulse Velocity (UPV), and the concentration of bacteria. Furthermore, it is observed that recycled aggregates possess inherent pores that allow for water absorption through these pores. Therefore, RCA is subjected to a 24-hour water immersion process before its incorporation into the concrete mix. While the compressive strength of the concrete remains consistent between RCA 0% and RCA 50%, it decreases significantly at RCA 100%. However, the performance of the bacteria exhibits proportionality to cell concentration. Notably, the effectiveness of the bacteria remains consistent regardless of changes in RCA proportions. This study underscores the promising potential of Bacillus bacteria in enhancing the durability and sustainability of concrete structures, with particular relevance to RCC applications. [ABSTRACT FROM AUTHOR]

Bioprocess optimization towards higher productivity and better quality control relies on real-time process monitoring tools to measure process and culture parameters. Cell concentration and viability are among the most important parameters to be monitored during bioreactor operations that are typically determined using optical methods on an extracted sample. In this paper, we have developed an online non-invasive sensor to measure cell concentration and viability based on Doppler ultrasound. An ultrasound transducer is mounted outside the bioreactor vessel and emits a high frequency tone burst (15 MHz) through the vessel wall. Acoustic backscatter from cells in the bioreactor depends on cell concentration and viability. The backscattered signal is collected through the same transducer and analyzed using multivariate data analysis (MVDA) to characterize and predict the cell culture properties. We have developed accurate MVDA models to predict the Chinese hamster ovary (CHO) cell concentration in a broad range from 0.1 × 106 cells/mL to 100 × 106 cells/mL, and cell viability from 3% to 99%. The non-invasive monitoring is ideal for single use bioreactor and the in-situ measurements removes the burden for offline sampling and dilution steps. This method can be similarly applied to other suspension cell culture modalities.

A novel image reconstruction method called multiple regression fitting electrical impedance spectro-tomography (mrf-EIST) has been proposed in order to realize the quantitative image reconstruction of dead cell fraction $\phi _{d}$ and cell concentration $c_{c}$ in a huge amount of cell environment. mrf-EIST statistically selects frequencies to extract two variables $\psi _{d}$ and $\psi _{c}$ , which quantify $\phi _{d}$ and $c_{c}$ , respectively. The $\phi _{d}$ and $c_{c}$ images are reconstructed by solving the inverse problem using $\psi _{d}$ and $\psi _{c}$ . To validate the performance of mrf-EIST, the image reconstruction by mrf-EIST in the frequency range from 100 Hz to 1 MHz is carried out under the condition that the number of cells is over 109 cells. As a result, mrf-EIST shows that the image quality defined by the difference in pixel value from the true image is less than 0.050 in $\phi _{d}$ and 0.071 in $c_{c}$ , respectively. In comparison to frequency-difference EIT (fd-EIT) as a conventional EIST regarding a position error of center of gravity, mrf-EIST provides much more accurate images, qualitatively and quantitatively, compared to the fd-EIT.

The goal of this study was to develop a rapid assessment of microalgal concentration using a turbidity meter to serve commercial shellfish hatcheries for feeding shellfish larvae and broodstock. We used four commonly used algal species, Tetraselmis suecica, Isochrysis galbana, Chaetoceros calcitrans, and Chaetoceros gracilis, generating serial dilutions of each and measuring cell concentrations and turbidity of each sample. We identified linear correlations between cell concentration and turbidity and established standard equations between cell concentration and turbidity for each species. We sampled and quantified algae from a shellfish hatchery using these equations and compared hemocytometer counts. No differences were found (P ≥ 0.174), indicating the accuracy of the equations. We expect that this method can provide a quick, accurate, easy method for shellfish hatcheries to quantify algal concentration and avoid either over- or underfeeding larvae and broodstock.

Abstract Xylose is the most abundant pentose sugar in lignocellulosic biomass and can be biologically converted into economically important products by microorganisms such as yeasts. This study aimed to characterize the bioconversion of xylose into xylitol and ethanol using four strains of Candida materiae belonging to the Spathaspora clade, which includes yeast species with the potential to convert D-xylose to xylitol and ethanol. Fermentation assays were performed in YPX medium (yeast extract, peptone, xylose 5%) under two oxygen-limiting conditions at inoculum concentrations of 1, 5 and 10 g L-1. The best results were obtained using a 5 g L-1 inoculum under moderate oxygen-limiting conditions. C. materiae UFMG-CM-Y480 produced 32.23 g L-1 of xylitol, yielding 0.743 g g-1 within 36 h. Different combinations of xylose and glucose (25/25 g L-1, 40/10 g L-1, 10/40 g L-1) were also used to verify the influence of sugars on C. materiae metabolism. Xylitol was preferentially produced in medium containing 40 g L-1 xylose. C. materiae UFMG-CM-Y480 produced 26.20 g L-1 of xylitol with a yield of 0.646 g g-1 in 36 h. Our results showed that C. materiae UFMG-CM-Y480 may convert D-xylose to xylitol with a better fermentative performance than other xylitol-producing yeasts.

Undergraduate students majoring in the life sciences benefit from experience with data analyses that connect mathematical calculations to the biological systems they are studying. Monitoring the optical density and cell number of Saccharomyces cerevisiae liquid cultures allows students to gain quantitative experience generating standard curves and trendlines that capture the relationship between optical density and cell concentration for a given S. cerevisiae strain. Data comparisons across multiple strains can yield insights into the biophysical properties of cells that drive light absorbance and scattering. In this Tips and Tools article, we share a laboratory module that allows students to experience cell biology tools, laboratory measurements, and data analysis to determine the mathematical relationship between optical density and cell concentration in liquid microbial cultures. This module could be integrated into undergraduate classes ranging from general biology to upper-level cell biology or microbiology and can be a starting point for more complex investigations of microbial growth.

Recently, even though 3D bioprinting has made it possible to fabricate 3D artificial tissues/organs, it still faces several significant challenges such as cell sedimentation and aggregation. As the essential element of 3D bioprinting, bioink is usually composed of biological materials and living cells. Guided by the initially dominant gravitational force, cells sediment, resulting in the non-uniformity of the bioink and the decrease in the printing reliability. This study primarily focuses on the quantification of cell sedimentation-induced cell concentration change and cell aggregation within the bioink reservoir during inkjet-based bioprinting. The major conclusions are summarized as follows: (1) with 0.5% (w/v) sodium alginate, after around 40-min printing time, almost all the cells have sedimented from the top region. The cell concentration at the bottom is measured to be more than doubled after 60-min printing time. On the contrary, due to the slow cell sedimentation velocity with 1.5% and 3% (w/v) sodium alginate, the uniformity of the bioink is still highly maintained after 60-min printing; and (2) more cell aggregates are observed at the bottom with the printing time, and severe cell aggregation phenomenon has been observed at the bottom using 0.5% (w/v) sodium alginate starting from 40-min printing time. With the highest cell concentration 2 × 106 cells/mL, 60.9% of the cells have formed cell aggregates at 40-min printing time. However, cell aggregation is dramatically suppressed by increasing the polymer concentration. [ABSTRACT FROM AUTHOR]

Aim. To estimate in vitro the effect of DNA isolated from the probiotic strain Bifidobacterium bifidum 791 on the cell concentration and adhesive properties of fecal isolates of bifidobacteria and opportunistic microorganisms of different species.Materials and methods. DNA was isolated from the probiotic strain Bifidobacterium bifidum 791. Biomass containing bifidobacteria was washed from the nutrient medium. The suspension of bacteria in the buffer solution was subjected to ultrasonic disintegration with a frequency of 40 kHz three times for 30 minutes, followed by centrifugation. The supernatants were combined and purified chromatographically on CL-4B Sepharose. B. breve, B. bifidum, B. infantis, Staphylococcus aureus, Escherichia coli lac-, Enterococcus faecalis, and Candida albicans were used as test cultures, isolated from the intestines of conditionally healthy adults. Results. The nucleic acid solution with a concentration of 3.54 |jg/ml did not affect the cell number of bifidobacteria (p = 0.61). The DNA content in the solution of 14.15-21.23 jg/ml increased the titers of B. bifidum and B. breve by 2 lg CFU/ml compared to the control (p = 0.01), but did not affect the titers of S. aureus, E. coli lac-, E. faecalis, C. albicans (p = 0.73). The DNA solution stimulated the self-aggregation of bifidobacteria in 1.5-2.0 times. The ability to autoaggregate under the influence of bifidobacterial DNA in S. aureus, E. faecalis, C. albicans did not change, in E. coli lacincreased 2.3 times (p = 0.05).Conclusion. A DNA solution of the probiotic strain B. bifidum 791 with a content 14.15-21.23 jg/ml stimulates the reproduction and autoaggregation of fecal B. breve, B. bifidum.

Recently, even though 3D bioprinting has made it possible to fabricate 3D artificial tissues/organs, it still faces several significant challenges such as cell sedimentation and aggregation. As the essential element of 3D bioprinting, bioink is usually composed of biological materials and living cells. Guided by the initially dominant gravitational force, cells sediment, resulting in the non-uniformity of the bioink and the decrease in the printing reliability. This study primarily focuses on the quantification of cell sedimentation-induced cell concentration change and cell aggregation within the bioink reservoir during inkjet-based bioprinting. The major conclusions are summarized as follows: (1) with 0.5% (w/v) sodium alginate, after around 40-min printing time, almost all the cells have sedimented from the top region. The cell concentration at the bottom is measured to be more than doubled after 60-min printing time. On the contrary, due to the slow cell sedimentation velocity with 1.5% and 3% (w/v) sodium alginate, the uniformity of the bioink is still highly maintained after 60-min printing; and (2) more cell aggregates are observed at the bottom with the printing time, and severe cell aggregation phenomenon has been observed at the bottom using 0.5% (w/v) sodium alginate starting from 40-min printing time. With the highest cell concentration 2 × 106 cells/mL, 60.9% of the cells have formed cell aggregates at 40-min printing time. However, cell aggregation is dramatically suppressed by increasing the polymer concentration.

Activated sludge process is the most common method for biological treatment of industrial and municipal wastewater. One of the most important parameters in performance of activated sludge systems is quantitative monitoring of biomass to keep the cell concentration in an optimum range. In this study, a novel method for activated sludge quantification based on image processing and RGB analysis is proposed. According to the results, the intensity of blue color in the macroscopic image of activated sludge culture can be a very accurate index for cell concentration measurement and R2 coefficient, Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Mean Absolute Percentage Error (MAPE) which are 0.990, 2.000, 0.323, and 13.848, respectively, prove this claim. Besides, in order to avoid the difficulties of working in the three-parameter space of RGB, converting to grayscale space has been applied which can estimate cell concentration with R2 = 0.99. Ultimately, an exponential correlation between RGB values and cell concentrations in lower amounts of biomass has been proposed based on Beer-Lambert law which can estimate activated sludge biomass concentration with R2 = 0.97 based on B index.

The study presents the design of a magnetic nanosystem functionalised with Escherichia coli for bacteriophage isolation. The chitosan‐coated nanoparticles (C‐MNP) were synthesised by coprecipitation, then functionalised with E. coli cells. Different concentrations of C‐MNP and incubation times were tested. The immobilisation kinetics and adsorption isotherm were studied. The kinetics was described with the pseudo‐stationary state after 30 min. The isotherm was linearized in the Freundlich model. Thermogravimetric analysis verified the functionalisation of C‐MNP with E. coli. The complex was used for the extraction of coliphage, for the analysis of the effect of time and salt concentration on phage desorption, and phage extractions with the reuse of the magnetic nanosystem. Compared with traditional methods, an increase in the phage titre collected with the nanocomplex was achieved. The obtained results suggest that C‐MNP/E. coli nanosystem can be used at least three cycles for the phage extraction. The release of the phages from the nanosystem was sensitive to the salt concentration. The use of a designed nano‐bio complex allowed a rapid and efficient separation of the phages from the water sample under the application of an external magnetic field, and with the possibility of reusing the magnetic complex. [ABSTRACT FROM AUTHOR]

Activated sludge process is the most common method for biological treatment of industrial and municipal wastewater. One of the most important parameters in performance of activated sludge systems is quantitative monitoring of biomass to keep the cell concentration in an optimum range. In this study, a novel method for activated sludge quantification based on image processing and RGB analysis is proposed. According to the results, the intensity of blue color in the macroscopic image of activated sludge culture can be a very accurate index for cell concentration measurement and R2 coefficient, Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Mean Absolute Percentage Error (MAPE) which are 0.990, 2.000, 0.323, and 13.848, respectively, prove this claim. Besides, in order to avoid the difficulties of working in the three-parameter space of RGB, converting to grayscale space has been applied which can estimate cell concentration with R 2 = 0.99. Ultimately, an exponential correlation between RGB values and cell concentrations in lower amounts of biomass has been proposed based on Beer-Lambert law which can estimate activated sludge biomass concentration with R 2 = 0.97 based on B index. [ABSTRACT FROM AUTHOR]

Previously, we demonstrated capture and concentration of Salmonella enterica subspecies enterica ser. Typhimurium using magnetic ionic liquids (MILs), followed by rapid isothermal detection of captured cells via recombinase polymerase amplification (RPA). Here, we report work intended to explore the broader potential of MILs as novel pre-analytical capture reagents in food safety and related applications. Specifically, we evaluated the capacity of the ([P66614+][Ni(hfacac)3−]) ("Ni(II)") MIL to bind a wider range of human pathogens using a panel of Salmonella and Escherichia coli O157:H7 isolates, including a "deep rough" strain of S. Minnesota. We extended this exploration further to include other members of the family Enterobacteriaceae of food safety and clinical or agricultural significance. Both the Ni(II) MIL and the ([P66614+][Dy(hfacac)4−]) ("Dy(III)") MIL were evaluated for their effects on cell viability and structure-function relationships behind observed antimicrobial activities of the Dy(III) MIL were determined. Next, we used flow imaging microscopy (FIM) of Ni(II) MIL dispersions made in model liquid media to examine the impact of increasing ionic complexity on MIL droplet properties as a first step towards understanding the impact of suspension medium properties on MIL dispersion behavior. Finally, we used FIM to examine interactions between the Ni(II) MIL and Serratia marcescens, providing insights into how the MIL may act to capture and concentrate Gram-negative bacteria in aqueous samples, including food suspensions. Together, our results provide further characterization of bacteria-MIL interactions and support the broader utility of the Ni(II) MIL as a cell-friendly capture reagent for sample preparation prior to cultural or molecular analyses. [ABSTRACT FROM AUTHOR]

BACKGROUND: Bone marrow mesenchymal stem cells have been extensively applied in animal experiments and clinical studies. The cell concentration, treatment times and results in each study are different, and there is no standard for optimal cell concentration. OBJECTIVE: To investigate the optimal concentration of bone mesenchymal stem cells injected into articular cavity in the treatment of rabbit cartilage defects. METHODS: Thirty 6-month-old New Zealand white rabbits were selected and randomly divided into control, 1×108, 1×109, 1×1010, and 1×1011/L groups. Cartilage defect models with diameter of 3 mm and depth of 2 mm were established in femoral trochlea in each group. One week after modeling, 1 mL of normal saline was injected into the rabbit’s knee of the control group. The other groups were injected with bone marrow mesenchymal stem cells at corresponding concentrations. After 6 and 12 weeks, gross observation, hematoxylin-eosin staining, Safranin-O-fast green-staining, type I and II collagen staining were performed to assess the cartilage regeneration. RESULTS AND CONCLUSION: In the control group, the defect area was obvious with no cartilage regeneration. The 1×108, 1×109, and 1×1010/L groups showed cartilage regeneration. The repairing effect was increased with the cell concentration increasing. The effect of cartilage repair in the 1×1011/L group was similar to that in the 1×1010/L group (P > 0.05). Therefore, 1×1010/L is the optimal concentration for intra-articular injection of bone marrow mesenchymal stem cells for treating cartilage defects, and higher concentration cannot enhance the repairing effect. [ABSTRACT FROM AUTHOR]

In 2016, specifications for both pre-cryopreserved and post-thawed cord blood were defined in the sixth edition of NetCord Foundation for the Accreditation of Cellular Therapy (FACT) Standards for Cord Blood Banks. However, for several experts, harmonization regarding flow cytometry analysis performed on post-thawed samples is still a concern. A multicenter study led by Héma-Québec aimed to provide scientific data to support the cord blood accreditation bodies such as NetCord FACT in the revision of standards. Twelve cord blood units were processed for plasma and red cell reduction following standard operating procedures. Cord blood unit aliquots were shipped to eight participating centers under cryogenic conditions for analysis before and after standardization of protocol. Repeatability of stem cell count, measured pre- and post-intervention with the centers, was estimated using multilevel linear regression models with a heterogeneous compound symmetry correlation structure among repeated measures. Excellent inter-center repeatability was reported by each participant regarding the viable CD34+ cells concentration, and a successful improvement effect of protocol standardization was also observed. However, we observed that better control over the critical parameters of the protocol did not have a significant effect on improving homogeneity in the enumeration of CD45+ cells. The current practice in cord blood selection should now also consider relying on post-thaw CD34+ concentration, providing that all cord blood banks or outsourcing laboratories in charge of the analysis of post-thaw CB samples take into account the consensual recommendations provided in this work and adhere to a good-quality management system. [ABSTRACT FROM AUTHOR]

Conventional sample preparation techniques require bulky and expensive instruments and are not compatible with next-generation point-of-care diagnostic testing. Here, we report a manually operated syringe-tip inertial microfluidic centrifuge (named i-centrifuge) for high-flow-rate (up to 16 mL/min) cell concentration and experimentally demonstrate its working mechanism and performance. Low-cost polymer films and double-sided tape were used through a rapid nonclean-room process of laser cutting and lamination bonding to construct the key components of the i-centrifuge, which consists of a syringe-tip flow stabilizer and a four-channel paralleled inertial microfluidic concentrator. The unstable liquid flow generated by the manual syringe was regulated and stabilized with the flow stabilizer to power inertial focusing in a four-channel paralleled concentrator. Finally, we successfully used our i-centrifuge for manually operated cell concentration. This i-centrifuge offers the advantages of low device cost, simple hand-powered operation, high-flow-rate processing, and portable device volume. Therefore, it holds potential as a low-cost, portable sample preparation tool for point-of-care diagnostic testing.

• Microalgae cells can affect the heat transfer characteristics of microalgae slurry. • The Nu formula of microalgae slurries in laminar tube flow was established. • The subcooled boiling of microalgae slurry caused the heat transfer deterioration. Continuous hydrothermal pretreatment in tubular reactors is a key process for the production of biofuel from microalgae biomass. Complex heat transfer characteristics of microalgae slurries, which consist of micron-sized cells suspended in water, are a challenge for the industrialization of hydrothermal pretreatment systems. In this study, the convective heat transfer characteristics of microalgae slurries flowing through a uniformly heated circular tube were experimentally investigated for the first time. The results revealed that the microalgae cell concentration and cell motion in the solid–liquid two-phase flow were the two main factors affecting the convective heat transfer characteristics of microalgae slurries in laminar tube flow. Considering the effects of the cell concentration, cell motion, viscosity variation with temperature and shear rate, and Peclet number, a novel correlation was proposed to predict the Nusselt number of microalgae slurries in laminar tube flow. In addition, a heat transfer deterioration phenomenon was observed under forced convection subcooled boiling conditions. This study provides guidance for the design and optimization of tubular heat exchangers in continuous hydrothermal pretreatment systems. [ABSTRACT FROM AUTHOR]

This paper presents an original design for a volume refractive index (RI) sensor for cell concentration detection based on the unique resonant optical tunneling effect (ROTE). In this design, the solution sample is introduced into the ROTE resonant cavity, whose reflection spectrum presents a large shift of its resonant dip in response to the tiny change of the solution RI. Performance calibration using the polystyrene particle solution indicates that the sensitivity is 19,000 nm/RIU and the total Q factor is 620. Experiments with hepatoma cells have obtained sensitivity values as high as 2.53 nm/(amol/ml) and a detection limit of 1.2 × 105 cells/ml. Compared with previously reported optical cell sensors, this original work implements the ROTE mechanism for the first time and presents superior device performance. Thus, the proposed design has a high potential for use in biomedical applications, such as drug discovery, cell research, and medical diagnoses. [ABSTRACT FROM AUTHOR]

Background: Nowadays, leaching-ore bacteria, especially Acidithiobacillus ferrooxidans is widely used to retrieve heavy metals, many researches reflected that extra adding microorganism could promote bioleaching efficiency by different mechanisms, but few of them discussed the interaction between microorganisms and based on growth model. This study aimed to provide theoretical support for the collaborative bioleaching of multiple microorganisms by using the Lotka–Volterra (L–V) model. Results: This study investigated the interaction of Acidithiobacillus ferrooxidans, Rhizobium phaseoli, and Rhodotorula sp. Results showed that the individual growth of the three microorganisms fit the logistic curves. The environmental capacities of A. ferrooxidans, R. phaseoli, and Rhodotorula sp. were 1.88 × 109, 3.26 × 108, and 2.66 × 108 cells/mL, respectively. Co-bioleaching showed mutualism between A. ferrooxidans and R. phaseoli with mutualism coefficients of α = 1.19 and β = 0.31, respectively. The relationship between A. ferrooxidans and Rhodotorula sp. could be considered as commensalism. The commensalism coefficient γ of the effect of Rhodotorula sp. on A. ferrooxidans was 2.45. The concentrations of A. ferrooxidans and R. phaseoli were 3.59 × 109 and 1.44 × 109 cells/mL in group E, respectively, as predicted by the model. The concentrations of A. ferrooxidans and Rhodotorula sp. were 2.38 × 109 and 2.66 × 108 cells/mL, respectively. The experimental peak values of the concentrations in microorganism groups E and F were detected on different days, but were quite close to the predicted values. Conclusion: The relationship among microorganisms during leaching could be described appropriately by Lotka–Volterra model between the initial and peak values. The relationship of A. ferrooxidans and R. phaseoli could be considered as mutualism, whereas, the relationship of A. ferrooxidans and R. phaseoli could be considered as commensalism.

Abstract Microbial oxidation of ferrous to ferric iron allows efficient oxidative processing of sulfide minerals under ambient conditions. This study determined the effect of cell concentration of a mixed mesophilic microbial culture on iron oxidation rate, and evaluated if there was a cell concentration threshold that dictates a maximal volumetric iron oxidation rate. A bioreactor with feedback-loading of ferrous media was operated at 30 °C to maintain a redox potential of +480 mV vs. Ag/AgCl at pH of 1.3. A positive and linear correlation (R2 = 0.955) between the cell concentration (6.8 × 107–7.1 × 109 cells mL−1) and volumetric biological iron oxidation (up to 6.9 g L−1 h−1) was observed. The specific iron oxidation was not affected by cell concentration, and no biocatalytic threshold was observed. This indicated that a high cell concentration can be used to achieve a high volumetric iron oxidation rate, enabling the use of a compact reactor size. Highlights • The effect of cell concentration on biological iron oxidation rate was evaluated. • Cell concentration correlated positively with volumetric iron oxidation rate. • Specific iron oxidation was not notably affected by cell concentration. • No biocatalytic threshold was observed in the cell concentration range tested. [ABSTRACT FROM AUTHOR]

To understand the effect of the hydrostatic pressure on Pseudanabaena galeata Böcher cells in both stratified and frequently mixed lakes, separate laboratory-scale models were developed. The pressure conditions in the stratified and mixed lakes were simulated in those models, and the variations of the cell and chlorophyll-a (Chl-a) concentration were analyzed. It was observed that an increase in pressure and darkness significantly reduced the cell concentration and pigmentation in P. galeata (p < 0.01, n = 3). After 10 days, the cell concentrations of P. galeata that were grown under conditions of a water depth of 30 m were reduced by 7.0%, per day, while the cell concentration rate after 10 days in atmospheric conditions was increased by 2.53% per day. During the experiment, cells were subjected to the prolonged darkness under 0.3 MPa pressure for 10 days and then exposed to the white light under atmospheric pressure for 5 days. Even after running this cycle for 60 days, 19.5% of the initial cells could survive. This rate exceeded the cell concentration-increasing rate in the control. These findings indicate that P. galeata has an adequate tolerance to pressure and fluctuating light irradiance and that the cells are able to propagate after escaping from those stress conditions. [ABSTRACT FROM AUTHOR]

Concentration measurement of particles in suspension is an important procedure performed in biological and clinical laboratories. Existing methods based on instruments such as hemocytometers, Coulter counters and flow cytometers are often laborious, destructive and incapable of in vivo measurements. On the other hand, an ultrasound-based method can be non-destructive and non-invasive and have the potential for in vivo measurement. In this work, a method is presented that estimates absolute particle concentration from high-frequency B-mode ultrasound images of a sample. The method is based on the detection and characterization of the echoes from individual particles to estimate the effective slice thickness of the image. Calibration using a reference sample is not required because the estimation is entirely image based. The particle type differential is also performed by using the backscatter coefficient of each detected echoes. The method is demonstrated by measuring microsphere suspensions as well as human T-cell suspensions. The proposed method has a wide range of potential clinical applications including non-invasive measurement of cell concentration in biological fluids such as cerebrospinal fluid. [ABSTRACT FROM AUTHOR]

The usefulness of ScepterTM cell counter analyzer (produced by Merck) was tested to assess the physiological and morphological state of distillers' yeast in conditions of ethanol stress. Yeast cells were divided into four size classes and on the basis of their structure, the physiological and morphological status of the analyzed yeast populations was determined. Measurements of the amount and size of yeast cells with the ScepterTM cell counter are simple, fast and accurate. This device has a large application potential in ethanolic fermentation studies using yeast both in scientific research and in industrial plants. [ABSTRACT FROM AUTHOR]

Microbial cells vary widely in size, specific density, shearing resistance, oxygen sensitivity and abundance so that differential harvesting and washing procedures are needed to efficiently recover cells from dilute suspensions. We here describe a mild, simple, variable and cost-efficient method to harvest cells on columns packed with silica beads. The method collects and concentrates 40–98% of the cells preserving enzymatic activity and cell viability. The method can be applied for strictly anaerobic microorganisms, is scalable to different culture volumes and can be multiplexed in standardized systems. We see major application potential in harvesting small cells leaking through 0.2 μm filters, for harvesting strictly anaerobic cells and for differential harvesting of cells according to cell size using a gradient system. [ABSTRACT FROM AUTHOR]