Plug-flow Bioreactor Research Articles

Simulation of Substrate, Microbial Interaction with Recycle using Matlab Computational Approach

This research outlines the microbial and substrate interaction in a plug flow bioreactor system for effective utilization of the substrate by the microorganism. To achieve this mathematical models were developed to monitor, predict and simulate the interaction characteristics of the bioreactor using the functional parameters for interaction of microbial and substrate concentration in a plug flow reactor system. The MATLAB computer program language was used to determine the interaction relationship between the substrate and microbial concentration upon the influence of bioreactor volume, space time and discharge time. The characteristics of the behavior in terms of decrease in substrate concentration with increase in microbial concentrate revealed the interaction in the bioreactor with recycle.

Biohydrogen production in an anaerobic baffled stacking reactor: Recirculation strategy and substrate concentration effects

This study designs a new type of anaerobic bioreactor based on prefabricated building wastewater treatment facility and plug flow bioreactor structures. This new reactor is named the anaerobic baffled stacking reactor (ABSR). The ABSR is divided into three reaction chambers. A liquid pump is established to recirculate the liquid in the second or third chambers to the first or second chamber to enhance the mass transfer reaction between the substrate and microorganisms. The recirculation pathway and substrate concentration effects of 10, 15, 20 and 30gCOD/L were investigated using sewage sludge as the seed inoculums at a hydraulic retention time of 8h, pH 5.5 and temperature 35°C. The results showed the biomass was accumulated at these recirculation strategies from the third to first, third to second and second to first chambers producing decreased carbohydrate utilization and hydrogen production efficiency. The third to first and second recirculation strategy could increase the disturbance efficiency, obtaining peak hydrogen content of 40±2.4%, hydrogen production rate 10.9±1.5L/L-d and hydrogen production yield 1.7±0.2molH2/mol Sucrose. The results reveals that ABSR has the advantages of biomass accumulation and well mixing. The ABSR is more suitable for anaerobic hydrogen production system.

Study of bioleaching under different hydraulic retention time for enhancing the dewaterability of digestate.

Dewatering of kitchen waste digestate is a key problem to solve so as to increase the application of kitchen waste after anaerobic digestion. In this study, the effects of bioleaching under different hydraulic retention time (HRT=2, 2.5, and 3days) on dewaterability of kitchen waste digestate were evaluated. A 12-stage plug flow bioreactor with 180L working volume was used for digestate bioleaching. The bioleached digestate under different HRTs were collected and dewatered by plate-and-frame filter press. The results showed that the moisture contents of digestate cakes were 67.87% at 2days of HRT, 58.06% at 2.5days of HRT, and 54.45% at 3days of HRT, respectively, indicating the longer the HRT, the lower the moisture content of filter cake. Balanced between the cost and practical need, 2.5days can be used as the HRT in engineering application. Under the condition of HRT of 2.5days, the pH, specific resistance to filtration (SRF), capillary suction time (CST), and sedimentation rate of digestate changed from the initial values of 8.08, 210.6s, 23.4×10(12)mkg(-1) and 10% to 3.21, 32.7s, 2.44×10(12)mkg(-1) and 76.8%, respectively. Based on the observations above, the authors conclude that bioleaching technology is an effective method to enhance digestate dewaterability and reduce the cost of subsequent reutilization.

Achieving low effluent NO3-N and TN concentrations in low influent chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio without using external carbon source

Two mathematical models were used to optimize the performance of a full-scale biological nutrient removal (BNR) activated treatment plant, a plug-flow bioreactors operated in a 3-stage phoredox process configuration, anaerobic anoxic oxic (A2/O). The ASM2d implemented on the platform of WEST2011 software and the BioWin activated sludge/anaerobic digestion (AS/AD) models were used in this study with the aim of consistently achieving the designed effluent criteria at a low operational cost. Four ASM2d parameters (the reduction factor for denitrification \((\eta _{NO_3 H} )\), the maximum growth rate of heterotrophs (µH), the rate constant for stored polyphosphates in PAOs (qpp), and the hydrolysis rate constant (kh)) were adjusted. Whereas three BioWin parameters (aerobic decay rate (bH), heterotrophic dissolved oxygen (DO) half saturation (KOA), and YP/acetic) were adjusted. Calibration of the two models was successful; both models have average relative deviations (ARD) less than 10% for all the output variables. Low effluent concentrations of nitrate nitrogen (N-NO3), total nitrogen (TN), and total phosphorus (TP) were achieved in a full-scale BNR treatment plant having low influent chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio (COD/TKN). The effluent total nitrogen and nitrate nitrogen concentrations were improved by 50% and energy consumption was reduced by approximately 25%, which was accomplished by converting the two-pass aerobic compartment of the plug-flow bioreactor to anoxic reactors and being operated in an alternating mode. Findings in this work are helpful in improving the operation of wastewater treatment plant while eliminating the cost of external carbon source and reducing energy consumption.

Hydrodynamic Mathematical Modelling of Aerobic Plug Flow and Nonideal Flow Reactors: A Critical and Historical Review

Existing mathematical models of wastewater treatment plants focus primarily on the bioconversion processes and often do not cope with the reactor hydrodynamics. However, in the literature several aerobic plug flow bioreactors with both kinetics modelling and hydrodynamics description are reported. The authors review mathematical models of aerobic plug flow reactors, such as activated sludge reactors, fluidized bed reactors, biofilters, and trickling filters focusing on their hydrodynamic approach and on the role of the reactor configuration on the process performance. For each reactor type the following modelling approach is compared: (a) ideal model, such as plug flow or complete mixed, (b) tank in series model, (c) dispersion model and (d) computational fluid dynamic model.

Evaluation of process conditions triggering emissions of green-house gases from a biological wastewater treatment system

In this study, methane (CH4) and nitrous oxide (N2O) emission dynamics of a plug–flow bioreactor located in a municipal full-scale wastewater treatment plant were monitored during a period of 10weeks. In general, CH4 and N2O gas emissions from the bioreactor accounted for 0.016% of the influent chemical oxygen demand (COD) and 0.116% of the influent total Kjeldahl nitrogen (TKN) respectively. In order to identify the emission patterns in the different zones, the bioreactor was divided in six different sampling sites and the gas collection hood was placed for a period of 2–3days in each of these sites. This sampling strategy also allowed the identification of different process perturbations leading to CH4 or N2O peak emissions. CH4 emissions mainly occurred in the first aerated site, and were mostly related with the influent and reject wastewater flows entering the bioreactor. On the other hand, N2O emissions were given along all the aerated parts of the bioreactor and were strongly dependant on the occurrence of process disturbances such as periods of no aeration or nitrification instability. Dissolved CH4 and N2O concentrations were monitored in the bioreactor and in other parts of the plant, as a contribution for the better understanding of the transport of these greenhouse gases across the different stages of the treatment system.

The Use of Immobilized Cytochrome P4502C9 in PMMA-Based Plug Flow Bioreactors for the Production of Drug Metabolites

Cytochrome P450 enzymes play a key role in the metabolism of pharmaceutical agents. To determine metabolite toxicity, it is necessary to obtain P450 metabolites from various pharmaceutical agents. Here, we describe a bioreactor that is made by immobilizing cytochrome P450 2C9 (CYP2C9) to a poly(methyl methacrylate) surface and, as an alternative to traditional chemical synthesis, can be used to biosynthesize P450 metabolites in a plug flow bioreactor. As part of the development of the CYP2C9 bioreactor, we have studied two different methods of attachment: (1) coupling via the N-terminus using N-hydroxysulfosuccinimide 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and (2) using the Ni(II) chelator 1-acetato-4-benzyl-triazacyclononane to coordinate the enzyme to the surface using a C-terminal histidine tag. Additionally, the propensity for metabolite production of the CYP2C9 proof-of-concept bioreactors as a function of enzyme attachment conditions (e.g., time and enzyme concentration) was examined. Our results show that the immobilization of CYP2C9 enzymes to a PMMA surface represents a viable and alternative approach to the preparation of CYP2C9 metabolites for toxicity testing. Furthermore, the basic approach can be adapted to any cytochrome P450 enzyme and in a high-throughput, automated process.

Homogenised model linking microscopic and macroscopic dynamics of a biofilm: Application to growth in a plug flow reactor

We propose a new “hybrid” model for the simulation of biofilm growth in a plug flow bioreactor, that combines information from three scales: a microscopic one for the individual bacteria, a mesoscopic or “coarse-grained” one that homogenises at an intermediate scale the quantities relevant to the attachment/detachment process, and a macroscopic one in terms of substrate concentration. In contrast to existing partial differential equations models, this approach is based on a description of biological mechanisms at the individual scale, thus bringing in a biological justification of the attachment/detachment process responsible of the macroscopic behaviour. We found that compared to purely individual based or purely macroscopic models,•the approximate coarse-grained scale simplifies the change of scales from micro to macro, and speeds up the computation,•additional information about the stochasticity of the solution, especially at small populations, is revealed compared with the numerical simulations of partial differential equations models. Furthermore, the coarse-grained model can be much more easily adapted to various attachment/detachment hypotheses, that are at the core of the biofilm development.

Biological lability of streamwater fluorescent dissolved organic matter

We investigated the biological lability of fluorescent dissolved organic matter (FDOM) from a temperate Piedmont stream. Plug‐flow bioreactors, colonized and maintained with natural stream water, were used to determine the concentrations of stream‐water biodegradable dissolved organic carbon (BDOC) and relative concentrations of FDOM within operationally defined biodegradability classes. Labile molecules with turnover times of hours are metabolized within the stream reach where they originated; semi‐labile molecules with turnover times of days travel out of the reach and are transported downstream before being metabolized; and a more recalcitrant class with a longer but undetermined turnover time flows through the river network without being metabolized. Between 26% and 31% of the DOC was biodegradable, with 8.6% labile and the balance semi‐labile. Humic‐like FDOM was a proxy for more recalcitrant DOM, exhibiting a ± 2% change as a function of increased bioreactor residence time. Humic‐like FDOM represents only the more recalcitrant and perhaps the more hydrophobic constituents and not the ecologically important semi‐labile humic substances within the BDOC pool. Tyrosine‐like and tryptophan‐like FDOM constituents included not only labile DOM, but also semi‐labile, and more recalcitrant moieties. For example, 13% of the tryptophan‐like FDOM was labile, 14% was semi‐labile, and 73% was more recalcitrant, while tyrosine‐like FDOM was 100% biodegraded and the majority (44–69%) was classified as labile. Collectively our results challenge some previous assessments of FDOM lability classifications and highlight the need to connect fluorescence characteristics of DOM to residence times of different carbon pools that spiral through a river network.

The application of a plug-flow reactor to measure the biodegradable dissolved organic carbon (BDOC) in seawater

Most of the ambient dissolved organic carbon (DOC) is refractory to microbial degradation; bacteria can consume a minor but variable part of the DOC pool over periods of hours and days. It is important to increase our knowledge of the dynamics of the biodegradable fraction of DOC (BDOC) to understand the global carbon budget. Several methods for determining BDOC have been developed; however, the problem of most of them is the time (days/weeks) required for the colonization and/or determination. In this paper, we describe the application to seawater of a plug-flow bioreactor to measure BDOC within 3–4 h. The bioreactor was built following Søndergaard and Worm [Søndergaard, M., Worm, J., 2001. Measurement of biodegradable dissolved organic carbon (BDOC) in lake water with a bioreactor. Water Res. 35, 2505-2513.] protocols for the measurement of BDOC in lake water. We analyzed BDOC on samples collected in the Gulf of Trieste during autumn–winter and summer 2003–2004. BDOC concentrations varied from 8 to 24 μM and represented from 10.3% to 25.5% of the total DOC. To evaluate the effectiveness of this method, we compared bioreactor BDOC measurement with data obtained from batch cultures. The results indicate that BDOC in coastal seawater can be measured rapidly and reliably with this bioreactor.

Catalytic removal of sulfide by an immobilized sulfide-oxidase bioreactor

A bioreactor packed with chitosan immobilized sulfide-oxidase from Streptomyces species LD048 was developed to treat a liquid stream of sulfide. The inoculation system was composed of glass with a 0.7 L working volume and enzyme activity of 2 mmol S g −1 carrier. The sulfide removal efficiency was almost 100% when the volumetric loading was increased up to 3.9 mmol S L −1 h −1 at a space velocity of 18 h −1. The maximal elimination capacity was 22.1 mmol S L −1 h −1 with a space velocity of 72 h −1. When the aeration was increased from 0.05 to 0.1 L min −1, the average removal efficiency improved from 81% to 94%. A removal efficiency of 90% was obtained after 15 days of operation with a load rate of 8.9 mmol S L −1 h −1 and a space velocity of 14.28 h −1. An operational equation based on the ideal plug flow bioreactor and the Michaelis–Menten model predicted the performance of this bioreactor.

Photopatterning Enzymes on Polymer Monoliths in Microfluidic Devices for Steady-State Kinetic Analysis and Spatially Separated Multi-Enzyme Reactions

A method for photopatterning multiple enzymes on porous polymer monoliths within microfluidic devices has been developed and used to perform spatially separated multienzymatic reactions. To reduce nonspecific adsorption of enzymes on the monolith, its pore surface was modified by grafting poly(ethylene glycol), followed by surface photoactivation and enzyme immobilization in the presence of a nonionic surfactant. Characterization of bound horseradish peroxidase (HRP) was carried out using a reaction in which the steady-state profiles of the fluorescent reaction product could be measured in situ and then analyzed using a plug-flow bioreactor model to determine the observed maximum reaction rate and Michaelis constant. The Michaelis constant of 1.9 micro mol/L agrees with previously published values. Mass-transfer limitations were evident at relatively low flow rates but were absent at higher flow rates. Sequential multienzymatic reactions were demonstrated using the patternwise assembly of two- and three-enzyme systems. Glucose oxidase (GOX) and HRP were patterned in separate regions of a single channel, and product formation was analyzed as a function of flow direction. Significant product formation occurred only in the GOX to HRP direction. A three-enzyme sequential reaction was performed using invertase, GOX, and HRP. All possible arrangements of the three enzymes were tested, but significant product formation was only observed when the enzymes were in the correct sequential order. Photopatterning enzymes on polymer monoliths provides a simple technique for preparing spatially localized multiple-enzyme microreactors capable of directional synthesis.

Continuous plug‐flow bioreactor: Experimental testing with Pseudomonas putida culture grown on benzoate

The goals of this work were to test the feasibility of a continuous plug-flow (PF) bioreactor and to compare the growth in the PF bioreactor to that in a batch bioreactor. A culture of Pseudomonas putida was pumped through a tube made of Teflon with varying residence times. The culture was aerated by pumping of air simultaneously with liquid medium to provide air bubbles along the tubular culture. When the residence time in the PF bioreactor was greater than the time needed to reach the stationary phase in batch mode, the maximum biomass density reached in PF mode was the same as the maximum density reached in the batch bioreactor, and benzoate (the only carbon and energy source) was completely consumed. The drawbacks for practical application of PF were found to be fluctuations of cell concentration in the outflow cultural liquid due to cell aggregation, significant cell adhesion to the inner wall of Teflon tubing, and inadequate aeration.

Superiority of 3-D Hematopoietic Stem Cell (HSC) & Stroma Cell Co-Cultures in Supporting the Proliferation of Transplantable HSC.

Stem cells are intimately associated in-vivo with discrete niches within the 3-dimensional (3-D) bone marrow micro-environment collectively provide molecular signals that mediate their differentiation and self-renewal. A recently developed Plug-Flow Bioreactor System (PluriXTM), which closely mimics the physiological bone marrow environment by combining 3-D stromal cultures with a continuous flow system, is capable of supporting long term maintenance/expansion of transplantable human HSC.The stroma cells, growing inside the PluriXTM bioreactor on porrosive carriers enable the propagation of high density (>100-fold input) 3-D stroma cell cultures for prolonged periods of time. Within 40 days, the number of primary human stroma cells seeded in the bioreactor at a density of 5*104 cells/ml reached 1.5*106 cells/ml and the stroma cell lines reached a density of 5*107–1*108 cells/ml. Three-dimensional static stroma HSC co-cultures were found to be superior to 2-D co-cultures in supporting the maintenance of CB HSC and early hematopoietic progenitors.When cord blood CD34+ cells were seeded on 2-D & 3-D stroma cell static cultures, the 3-D stroma cultures proved superior in supporting the growth of CD34+, CD34+38− and CD34+38−CXCR4+ cells. The 3-D primary human stroma static cultures supported these cells 4.7, 22, 7.4 fold better than the 2-D cultures, respectively.The CD34+ cells seeded on the high-density 3-D stroma cell cultures within the PluriXTM bioreactor demonstrated significant superiority to 2-D and 3-D stroma cell static cultures and 2-D stroma cultures in supporting the growth and expansion of HSC and earlier hematopoietic progenitors.These findings verify that a system based on 3-D stroma co-cultures is preferable for ex-vivo expansion of human HSC's. The PluriXTM system offers wide-range potential for expansion of stem cells from cord blood and production of specific blood products.

Multienzyme mevalonate pathway bioreactor.

The five-carbon metabolic intermediate isopentenyl diphosphate constitutes the basic building block for the biosynthesis of all isoprenoids in all forms of life. Two distinct pathways lead from amphibolic intermediates to isopentenyl diphosphate. The Gram-positive cocci and certain other pathogenic bacteria employ exclusively the mevalonate pathway, a set of six enzyme-catalyzed reactions that convert 3 mol of acetyl-CoA to 1 mol each of carbon dioxide and isopentenyl diphosphate. The survival of the Gram-positive cocci requires a fully functional set of mevalonate pathway enzymes. These enzymes therefore represent potential targets of inhibitors that might be employed as antibiotics directed against multidrug-resistant strains of certain bacterial pathogens. A rapid throughput, bioreactor-based assay to assess the effects of potential inhibitors on several enzymes simultaneously should prove useful for the survey of candidate inhibitors. To approach this goal, and as a proof of concept, we employed enzymes from the Gram-positive pathogen Enterococcus faecalis. Purified recombinant enzymes that catalyze the first three reactions of the mevalonate pathway were immobilized in two kinds of continuous flow enzyme bioreactors: a classical hollow fiber bioreactor and an immobilized plug flow bioreactor that exploited a novel method of enzyme immobilization. Both bioreactor types employed recombinant acetoacetyl-CoA thiolase, HMG-CoA synthase, and HMG-CoA reductase from E. faecalis to convert acetyl-CoA to mevalonate, the central intermediate of the mevalonate pathway. Reactor performance was monitored continuously by spectrophotometric measurement of the concentration of NADPH in the reactor effluent. Additional potential applications of an Ni(++) affinity support bioreactor include using recombinant enzymes from extremophiles for biosynthetic applications. Finally, linking a Ni(++) affinity support bioreactor to an HPLC-mass spectrometer would provide an experimental and pedagogical tool for study of metabolite flux and pool sizes of intermediates to model regulation in intact cells.

Profiles of bacterial community composition and metabolic potential through a plug-flow bioreactor fed with lake water

Bacterial community composition and metabolic potential changed through a bioreactor. Analyses of gradients in bioreactors may be an alternative to conventional approaches attempting to unravel the phenotype of bacterioplankton phylotypes.

Bioprocess kinetics in a horizontal rotating tubular bioreactor.

A horizontal rotating tubular bioreactor (HRTB) is a plug flow bioreactor whose interior is provided with O-ring-shaped partition walls that serve as carriers for microbial biomass. During this investigation, microbial biomass was grown in suspension and on the bioreactor inner surface as a microbial biofilm with average mass that was considerably higher than suspended biomass. The dynamics of bioprocess in HRTB was studied by different combinations of process parameters (bioreactor rotation speed and mean residence time) and it was monitored by withdrawing the samples from five positions along the bioreactor. During this investigation it was also observed that mean residence time had a more pronounced effect on the bioprocess dynamics than bioreactor rotation speed. For the description of bioprocess kinetics in HRTB an unstructured kinetic model was established that defines biomass growth, product formations and substrate consumption rate by using a modified Monod (Levenspiel) model. This kinetic model defines changes in suspension and in microbial biofilm, and it shows relatively good agreement with experimental data.

Reaction Kinetics of Immobilized-Cell Denitrification. I: Background and Model Development

A simplified, quasi-steady-state model has been formulated for groundwater denitrification using immobilized cells. The model takes into account the diffusion-limited penetration of nitrate and nitrite into the immobilized-cell biocatalyst particle, uniform intraparticle cell density, equivalent slab geometry for the spherical particle, zero-order intrinsic reaction kinetics of the immobilized cells, sequential reduction of nitrate to nitrite and nitrite to dinitrogen within the particle, no inhibition of the sequential reactions by either nitrate or nitrite, and ideal plug flow conditions in the bioreactor. As a result, the reaction in the bulk fluid of the plug-flow bioreactor can be described by a half-order kinetics, and the process is characterized by the half-order reaction rate constants for nitrate and nitrite reduction. These constants incorporate the intrinsic reaction kinetics of the immobilized cells, the size and packing density of biocatalyst particles in the reactor, and the effective diffusion coefficients of nitrate and nitrite in the particle matrix.

Measurement of biodegradable dissolved organic carbon (BDOC) in lake water with a bioreactor

Once-through, plug-flow bioreactors were colonised and maintained with a microbial community from a mesotrophic lake and used to measure the concentration of biodegradable dissolved organic carbon (BDOC). A BDOC measurement can be done within 3–4 h by this method. Glucose was used to test whether oxygen consumption (BOD) could substitute for measurements of dissolved organic carbon (DOC). All added glucose was utilised, however, without a concomitant increase in oxygen demand. Oxygen consumption should not be used in bioreactor measurements. The site-specificity was tested by comparing DOC utilisation in bioreactors with batch cultures inoculated with indigenous bacteria and incubated for 28 days. The bioreactors were not site-specific and required no acclimation to measure BDOC from three different systems. However, humic substances were adsorbed in the reactors and about two days were needed to equilibrate the reactors. The BDOC concentrations in two lakes varied 2-fold over diurnal cycles and 3-fold during the period February–June. No significant relations to the light/dark cycle, chlorophyll, and DOC were found. The absolute BDOC concentrations ranged from 20 to almost 200 μM and averaged 13% of the DOC in the lakes. It is concluded that BDOC in lakes and other fresh waters can be measured quickly and reliably with a bioreactor.

Esterification of oleic acid and ethanol in plug flow (packed bed) reactor under supercritical conditions: Investigation of kinetics

The present work provided the reaction kinetic data, required to predict the performance of packed-bed plug flow bioreactor operating under supercritical conditions. It investigated the kinetics of esterification of oleic acid and ethanol. Biocatalyst Lypozyme™ IM60, which is lipase from Rhizomucor miehei immobilised on Duolite (an ion exchange resin), was employed to synthesise ethyl oleate. Experimentally, esterification was carried out using a range of oleic acid- and ethanol concentrations, respectively. The effect of water concentration on the enzyme activity was also investigated. Analytically, the reaction mechanism was investigated by a series of kinetic analysis using the Direct Linear, the Primary and the Burke–Lineweaver (double reciprocal) plots. The reaction was modelled by the Henri–Michaelis–Menten equation and the reaction constants, namely K m and V max, were evaluated. It was found that the initial water concentration in the system effected the enzyme initial activity in a bell-like manner, giving an optimum (enzyme activity,and water concentration) value for each alcohol concentration. Furthermore, it was found that under higher alcohol concentrations, the reaction experienced substrate inhibition. The latter was identified to be competitive inhibition under moderate alcohol concentrations and non-competitive inhibitions under high alcohol concentrations. Hence, reaction inhibition constant value K i was calculated.