The Influence of Fluid Mixed State on Microorganisms: A Test Case with Bacillus subtilis

2014 ◽  
Vol 1073-1076 ◽  
pp. 165-171
Author(s):  
Quan Liu ◽  
Wen Jie Zhang ◽  
Jian Shi
Keyword(s):  
Reynolds Number ◽  
Bacillus Subtilis ◽  
Dissolved Oxygen ◽  
Biological Treatment ◽  
Fluid Mixing ◽  
Logarithmic Phase ◽  
Test Case ◽  
Stationary Growth ◽  
Liquid Fluidization ◽  
Growth Of Bacteria

Flow pattern and mode have a far influence on the efficiency of biological treatment systems. In order to investigate the effects of different flow patterns on the growth of Bacillus subtilis, a self-developed fluid mixing device was designed to produce different liquid fluidization. It was found that the greater Re, the more conducive to the growth of bacteria, which evidenced by the logarithmic phase shorter and reached stationary phase bacteria concentration increased; when the Reynolds number is low, growth curve of Bacillus subtilis appeared Growth - stationary - growth and cell precipitation phenomenon, both phenomena gradually disappeared when Re increases. Besides, it can consume dissolved oxygen after inoculation with Bacillus subtilis, which keeping the dissolved oxygen in the medium at a lower level (0~1mg/L)

scholarly journals Turbulence model performance for ventilation components pressure losses

2021 ◽  
Author(s):  
Karsten Tawackolian ◽  
Martin Kriegel
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Pressure Loss ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Test Case ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Near Wall

AbstractThis study looks to find a suitable turbulence model for calculating pressure losses of ventilation components. In building ventilation, the most relevant Reynolds number range is between 3×104 and 6×105, depending on the duct dimensions and airflow rates. Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×105. An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence. Most of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers. Viscous effects near walls played an important role in the present simulations. In turbulence modelling, near-wall damping functions are used to account for this influence. A model that implements near-wall modelling is the lag elliptic blending k-ε model. This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers. Another example is the low Reynolds number k-ε turbulence model of Wilcox (LRN). The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings. It has not been widely used for internal flows such as air duct flows. Based on selected reference cases, the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components. Improved predictions were obtained with new coefficients (LRNM model). This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this application. Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.

scholarly journals Elements in the Interpretation of Platinum Electrode Potentials in Biological Treatment

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1335-1344 ◽  
Author(s):  
A. Heduit ◽  
D. R. Thevenot
Keyword(s):  
Dissolved Oxygen ◽  
Biological Treatment ◽  
Platinum Electrode ◽  
Surface Characteristics ◽  
Electrode Potentials ◽  
Zero Current ◽  
Experimental Values ◽  
Mixed Potentials ◽  
Ionic Forms ◽  
Current Potential

The zero current potential of a platinum electrode in a biological medium (wastewater, activated sludge) is strongly dependent on the surface characteristics of the metal. It is also influenced by pH (probably Pt/PtO system), dissolved oxygen (O2/OH- system), and ionic forms of nitrogen (NO2-/NH4+ and NO3-/NO2-systems). The experimental values of the coefficients relating the stabilized potential of a platinum electrode to the logarithm of the concentration of the elements under consideration (Nernst equations) are significantly different from the thermodynamic coefficients corresponding to each reaction. The platinum is thus not in equilibrium with the dissolved redox reactants and is likely subject to mixed potentials in which the adsorbed components play an important role.

Adjoint-Based Aerodynamic Shape Optimization for Low Reynolds Number Airfoils

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Juanmian Lei ◽  
Jiandong He
Keyword(s):  
Reynolds Number ◽  
Shape Optimization ◽  
Low Reynolds Number ◽  
Boundary Layer Separation ◽  
Small Scale ◽  
Test Case ◽  
Aerodynamic Shape Optimization ◽  
Aerodynamic Shape ◽  
Aerial Vehicles ◽  
Low Reynolds

In the past decades, most of the research studies on airfoil shape design and optimization were focused on high Reynolds number airfoils. However, low Reynolds number airfoils have attracted significant attention nowadays due to their vast applications, ranging from micro-aerial vehicles (MAVs) to small-scale unmanned aerial vehicles. For low Reynolds number airfoils, the unsteady effects caused by boundary layer separation cannot be neglected. In this paper, we present an aerodynamic shape optimization framework for low Reynolds number airfoil that we developed based on the unsteady laminar N–S equation and the adjoint method. Finally, using the developed framework, we performed a test case with NACA0012 airfoil as a baseline configuration and the inverse of lift to drag ratio as the cost function. The optimization was carried out at Re = 10,000 and Ma = 0.2. The results demonstrate the effectiveness of the framework.

The Rationale for the Fish Farms Circulating Water Biological Treatment Intensification

2018 ◽  
Vol 931 ◽  
pp. 979-984
Author(s):  
Sergey V. Starovoytov ◽  
Ahmed S. Khalil ◽  
Nikolai S. Serpokrylov
Keyword(s):  
Dissolved Oxygen ◽  
Biological Treatment ◽  
Treatment Intensification ◽  
Fish Farms ◽  
Water Pollutants ◽  
Circulating Water ◽  
Air Supply ◽  
Symbiotic Community

Aerobic biological treatment of waters in artificial conditions is carried out by symbiotic algobacterial community of attached and free-floating organisms in various types of aerotank and biofilters. With the blowers and mixers of different designs, the biomass is saturated with oxygen. Controlled air supply provides the necessary concentration of dissolved oxygen and stimulates the oxidation of organic and inorganic water pollutants symbiotic community.

scholarly journals Numerical Study of T-Shaped Micromixers with Vortex-Inducing Obstacles in the Inlet Channels

Micromachines ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1122
Author(s):  
Chih-Yang Wu ◽  
Bing-Hao Lai
Keyword(s):  
Fluid Dynamics ◽  
Reynolds Number ◽  
Particle Tracking ◽  
Concentration Distribution ◽  
Numerical Study ◽  
Fluid Mixing ◽  
Sudden Increase ◽  
New Approach ◽  
Mixing Performance ◽  
Flow Modification

To enhance fluid mixing, a new approach for inlet flow modification by adding vortex-inducing obstacles (VIOs) in the inlet channels of a T-shaped micromixer is proposed and investigated in this work. We use a commercial computational fluid dynamics code to calculate the pressure and the velocity vectors and, to reduce the numerical diffusion in high-Peclet-number flows, we employ the particle-tracking simulation with an approximation diffusion model to calculate the concentration distribution in the micromixers. The effects of geometric parameters, including the distance between the obstacles and the angle of attack of the obstacles, on the mixing performance of micromixers are studied. From the results, we can observe the following trends: (i) the stretched contact surface between different fluids caused by antisymmetric VIOs happens for the cases with the Reynolds number (Re) greater than or equal to 27 and the enhancement of mixing increases with the increase of Reynolds number gradually, and (ii) the onset of the engulfment flow happens at Re≈125 in the T-shaped mixer with symmetric VIOs or at Re≈140 in the standard planar T-shaped mixer and results in a sudden increase of the degree of mixing. The results indicate that the early initiation of transversal convection by either symmetric or antisymmetric VIOs can enhance fluid mixing at a relatively lower Re.

Analysis of the Crushing Effect about Ultrasound on E. coli and B. subtilis

2012 ◽  
Vol 260-261 ◽  
pp. 1017-1021
Author(s):  
Xin Ying Wang ◽  
Yong Tao Liu ◽  
Min Hui ◽  
Ji Fei Xu
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Bacillus Subtilis ◽  
Bacterial Cell ◽  
Logarithmic Phase ◽  
Growth Stages ◽  
Bacterial Cells ◽  
E Coli ◽  
Different Growth Stages ◽  
Main Factor

Escherichia coli and Bacillus subtilis as objects of the study, ultrasonic fragmentation acted on the bacterial cells in different growth stages, results showed that, it’s similar to the crushing effect of ultrasound on E. coli and B. subtilis cells of different growth stages, the highest crushing rate in the logarithmic phase, reached to 95.8% and 94.3% respectively, the crushing rate of adjustment phase is lowest, maintained at around 60%, the crushing rate stability cell was centered, which can be achieved 90%. The structure of the bacterial cell wall didn’t the main factor to decide the ultrasonic fragmentation effect, but different growth periods of bacterial cells did the determinant.

Bacillus subtilis AprX involved in degradation of a heterologous protein during the late stationary growth phase

2007 ◽  
Vol 104 (2) ◽  
pp. 135-143 ◽  
Author(s):  
Takeko Kodama ◽  
Keiji Endo ◽  
Kazuhisa Sawada ◽  
Katsutoshi Ara ◽  
Katsuya Ozaki ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Growth Phase ◽  
Heterologous Protein ◽  
Stationary Growth Phase ◽  
Stationary Growth

scholarly journals Inferring Biological Mechanisms by Data-Based Mathematical Modelling: Compartment-Specific Gene Activation during Sporulation in Bacillus subtilis as a Test Case

2011 ◽  
Vol 2011 ◽  
pp. 1-12 ◽  
Author(s):  
Dagmar Iber
Keyword(s):  
Bacillus Subtilis ◽  
Gene Activation ◽  
Experimental Information ◽  
Specific Gene ◽  
Model Parameters ◽  
Test Case ◽  
Detailed Model ◽  
Wide Range ◽  
Technical Advances ◽  
Biological Functionality

Biological functionality arises from the complex interactions of simple components. Emerging behaviour is difficult to recognize with verbal models alone, and mathematical approaches are important. Even few interacting components can give rise to a wide range of different responses, that is, sustained, transient, oscillatory, switch-like responses, depending on the values of the model parameters. A quantitative comparison of model predictions and experiments is therefore important to distinguish between competing hypotheses and to judge whether a certain regulatory behaviour is at all possible and plausible given the observed type and strengths of interactions and the speed of reactions. Here I will review a detailed model for the transcription factor , a regulator of cell differentiation during sporulation in Bacillus subtilis. I will focus in particular on the type of conclusions that can be drawn from detailed, carefully validated models of biological signaling networks. For most systems, such detailed experimental information is currently not available, but accumulating biochemical data through technical advances are likely to enable the detailed modelling of an increasing number of pathways. A major challenge will be the linking of such detailed models and their integration into a multiscale framework to enable their analysis in a larger biological context.

scholarly journals Molecular Organization of Intrinsic Restriction and Modification Genes BsuM of Bacillus subtilis Marburg

2002 ◽  
Vol 184 (2) ◽  
pp. 381-389 ◽  
Author(s):  
Hideyuki Ohshima ◽  
Satoshi Matsuoka ◽  
Kei Asai ◽  
Yoshito Sadaie
Keyword(s):  
Bacillus Subtilis ◽  
Dna Methyltransferases ◽  
Open Reading Frames ◽  
Molecular Organization ◽  
Transcriptional Analysis ◽  
Logarithmic Phase ◽  
Modification System ◽  
Target Sequences ◽  
Reading Frames ◽  
Classical Mutant

ABSTRACT Transcriptional analysis and disruption of five open reading frames (ORFs), ydiO, ydiP, ydiR, ydiS, and ydjA, in the prophage 3 region of the chromosome of Bacillus subtilis Marburg revealed that they are component genes of the intrinsic BsuM restriction and modification system of this organism. The classical mutant strain RM125, which lacks the restriction and modification system of B. subtilis Marburg, lacks the prophage 3 region carrying these five ORFs. These ORFs constitute two operons, the ydiO-ydiP operon and the ydiR-ydiS-ydjA operon, both of which are expressed during the logarithmic phase of growth. The predicted gene products YdiO and YdiP are the orthologues of cytosine DNA methyltransferases. The predicted YdiS product is an orthologue of restriction nucleases, while the predicted YdiR and YdjA products have no apparent paralogues and orthologues whose functions are known. Disruption of the ydiR-ydiS-ydjA operon resulted in enhanced transformation by plasmid DNA carrying multiple BsuM target sequences. Disruption of ydiO or ydiP function requires disruption of at least one of the following genes on the chromosome: ydiR, ydiS, and ydjA. The degrees of methylation of the BsuM target sequences on chromosomal DNAs were estimated indirectly by determining the susceptibility to digestion with XhoI (an isoschizomer of BsuM) of DNAs extracted from the disruptant strains. Six XhoI (BsuM) sites were examined. XhoI digested at the XhoI sites in the DNAs from disruptants with disruptions in both operons, while XhoI did not digest at the XhoI sites in the DNAs from the wild-type strain or from the disruptants with disruptions in the ydiR-ydiS-ydjA operon. Therefore, the ydiO-ydiP operon and the ydiR-ydiS-ydjA operon are considered operons that are responsible for BsuM modification and BsuM restriction, respectively.

scholarly journals RelA Protein Is Involved in Induction of Genetic Competence in Certain Bacillus subtilis Strains by Moderating the Level of Intracellular GTP

2002 ◽  
Vol 184 (14) ◽  
pp. 3923-3930 ◽  
Author(s):  
Takashi Inaoka ◽  
Kozo Ochi
Keyword(s):  
Bacillus Subtilis ◽  
High Performance ◽  
Stationary Growth Phase ◽  
Competence Development ◽  
Stationary Growth ◽  
Transcriptional Fusion ◽  
Auxotrophic Strain ◽  
Genetic Competence ◽  
Physiological Conditions ◽  
Fusion Analysis

ABSTRACT We found that the ability to develop genetic competence of a certain relaxed (relA) aspartate-auxotrophic strain of Bacillus subtilis is significantly lower than that of the isogenic stringent (relA +) strain. Transcriptional fusion analysis utilizing a lacZ reporter gene indicated that the amount of the ComK protein, known as the key protein for competence development, is greatly reduced in the relaxed strain than in the stringent strain. We also found that the addition of decoyinine, a GMP synthetase inhibitor, induces expression of a competence gene (comG) in the relaxed strain, accompanied by a pronounced decrease in the level of intracellular GTP as measured by high-performance liquid chromatography. The transformation efficiency of the relaxed strain increased 100-fold when decoyinine was added at t0 (the transition point between exponential to stationary growth phase). Conversely, supplementation of guanosine together with decoyinine completely abolished the observed effect of adding decoyinine on competence development. Furthermore, the impaired ability of the relaxed strain for competence development was completely restored by disrupting the codY gene, which is known to negatively control comK expression. Our results indicate that the RelA protein plays an essential role in the induction of competence development at least under certain physiological conditions by reducing the level of intracellular GTP and overcoming CodY-mediated regulation.

Sign in / Sign up

Export Citation Format

Share Document