Continuous-flow Reactor System Research Articles

Brewer's yeast cell wall affects microbiota composition and decreases Bacteroides fragilis populations in an anaerobic gut intestinal model

Brewer's yeast cell wall (BYC) has been reported to have prebiotic activity that improves the microbiotal composition of the human gut. To understand the precise effect of BYC on gut microbiota and its metabolism, we used a three-stage continuous-flow reactor system that mimicked the environment of the large intestine. The reactor system was able to maintain the bacterial community stably for a week. The Bacteroides fragilis population decreased drastically after the addition of BYC into this system while the number of Lactobacillus was stably maintained. In addition, propionate and acetate levels increased drastically. This metabolic change correlated with an increase in a number of specific operational taxonomic units annotated to the genus Veillonella and Megasphaella. These results suggest that BYC affects the composition of microbiota in an in vitro model system.

Alkalinity Generation in a Novel Multi-stage High-strength Acid Mine Drainage and Municipal Wastewater Passive Co-treatment System

Passive co-treatment of high-strength acid mine drainage (AMD) and municipal wastewater (MWW) was examined in a laboratory-scale, four-stage continuous flow reactor system with a total residence time of 6.6 d. Synthetic AMD of pH 2.60 and an acidity of 1,870 mg/L (as CaCO3) was mixed at a 1:2 ratio with raw MWW (pH 7.67, 288 mg/L alkalinity (as CaCO3), and 265 mg/L BOD5) from the City of Norman, Oklahoma and introduced into the system. Alkalinity generated by limestone dissolution and bacterial SO4 2− reduction (BSR) processes was sufficient to support various metal removal processes and produce an effluent with circumneutral pH (6.98) and a net alkalinity of 10.4 mg/L (as CaCO3). Alkalinity generation from limestone dissolution was comparable with conventional AMD passive treatment systems. BSR proceeded at a relatively high rate (0.56 mol/m3 day) despite inhibitory pH and metals concentrations. Results indicate that the diverse electron donors in the MWW may be as suitable for BSR and their supporting microbial communities as commonly used substrates, presenting an opportunity to use a common waste as a resource for passive treatment.

Highly effective reduction of fecal indicator bacteria counts in an ecologically engineered municipal wastewater and acid mine drainage passive co-treatment system

Passive co-treatment of municipal wastewater and synthetic acid mine drainage in a laboratory-scale, four-stage continuous flow reactor system was examined for changes in fecal indicator bacteria (FIB) counts. Raw municipal wastewater (MWW) from the City of Norman, Oklahoma was mixed at a 2:1 ratio with high-strength synthetic acid mine drainage and introduced to the system. The MWW contained varying concentrations of total coliforms (TC), fecal coliforms (FC), Escherichia coli, and fecal streptococci (FS). Initial concentrations ranged from 6 to 13, 0.6 to 6, 3 to 5, and 0.1 to 0.7 million cfu/100 mL, for TC, FC, E. coli, and FS, respectively. During the 6.6-day system residence time, a 100% reduction of all FIB was observed. However, FIB exhibited evidence of sub-lethal injury with slower colony formation rates on standard growth media after 81 h of retention. Extending standard incubation periods resulted in higher concentrations of all FIB in each treatment stage, except the final stage where only E. coli and TC counts increased. Although this co-treatment regime reduced FIB concentrations more effectively than conventional active or passive MWW treatment systems, further work can be done to optimize the efficiency of treating these wastes simultaneously.

Access to small size distributions of nanoparticles by microwave-assisted synthesis. Formation of Ag nanoparticles in aqueous carboxymethylcellulose solutions in batch and continuous-flow reactors

This article examines the effect(s) of the 2.45-GHz microwave (MW) radiation in the synthesis of silver nanoparticles in aqueous media by reduction of the diaminesilver(i) complex, [Ag(NH(3))(2)](+), with carboxymethylcellulose (CMC) in both batch-type and continuous-flow reactor systems with a particular emphasis on the characteristics of the microwaves in this process and the size distributions. This microwave thermally-assisted synthesis is compared to a conventional heating (CH) method, both requiring a reaction temperature of 100 degrees C to produce the nanoparticles, in both cases leading to the formation of silver colloids with different size distributions. Reduction of the diaminesilver(i) precursor complex, [Ag(NH(3))(2)](+), by CMC depended on the solution temperature. Cooling the reactor during the heating process driven with 390-Watt microwaves (MW-390W/Cool protocol) yielded silver nanoparticles with sizes spanning the range 1-2 nm. By contrast, the size distribution of Ag nanoparticles with 170-Watt microwaves (no cooling; MW-170W protocol) was in the range 1.4-3.6 nm (average size approximately 3 nm). The overall results suggest the potential for a scale-up process in the microwave-assisted synthesis of nanoparticles. Based on the present data, a flow-through microwave reactor system is herein proposed for the continuous production of silver nanoparticles. The novel flow reactor system (flow rate, 600 mL min(-1)) coupled to 1200-Watt microwave radiation generated silver nanoparticles with a size distribution 0.7-2.8 nm (average size ca. 1.5 nm).

Estrogen Concentration Affects its Biodegradation Rate in Activated Sludge

The effect of concentration on the biodegradation rate of the steroid estrogens, estrone (E1) and 17-alpha-ethinylestradiol (EE2), was studied in batch and continuous-flow reactor systems using fresh activated sludge from two sewage treatment plants. Between the concentrations of 0.03 to 10 μg/L in the batch system no consistent difference was found in the biodegradation rates for either estrogen. The biodegradation half-life was 0.3 to 0.7 h for E1, and 1.5 to 4.4 h for EE2 at 15 to 20°C. However, at 100 μg/L, biodegradation rates for both estrogens decreased, with the half-life prolonged to around 2.5 h for E1 and 12 to 18 h for EE2. In continuous-flow experiments, over a 2 h residence time, 95% of E1 and 48% of EE2 were removed on average at 0.1 μg/L, whilst 52% of E1 and 20% of EE2 were removed at 100 μg/L. In general, spiking concentration of estrogens did not appear to affect biodegradation rates between the ng/L to low μg/L levels in activated sludge; however, the rates greatly slowed down when the concentration increased up to 100 μg/L. The results suggest activated sludge biodegradation studies with estrogens in the high μg/L levels could give misleading results and should be avoided.

Continuous tubular flow reactor for XAFS studies of organometallic reactions: Possibilities and limitations for studies of the Soai reaction

A computer-controlled continuous tubular flow reactor system has been commissioned that permits time-resolved in situ XAFS measurements of organometallic reactions. The system was commissioned by Zn K-edge measurements of products formed during the Soai reaction. XANES data are shown that illustrate the quality of the data that can be achieved. The XANES spectra are compatible with the presence of dimer, trimer or other oligomeric alkoxide species in the Soai process. It is shown how heterogeneity in the Soai reaction system leads to considerable complications with the measurements due to the formation of floating particles of the aldehyde/iPr2Zn adduct formed in the reaction; additionally, decomposition of iPr2Zn with residual air and moisture leads to deposits on cell walls.

Engineering of bio-hybrid materials by electrospinning polymer-microbe fibers

Although microbes have been used in industrial and niche applications for several decades, successful immobilization of microbes while maintaining their usefulness for any desired application has been elusive. Such a functionally bioactive system has distinct advantages over conventional batch and continuous-flow microbial reactor systems that are used in various biotechnological processes. This article describes the use of polyethylene oxide(99)-polypropylene oxide(67)-polyethylene oxide(99) triblock polymer fibers, created via electrospinning, to encapsulate microbes of 3 industrially relevant genera, namely, Pseudomonas, Zymomonas, and Escherichia. The presence of bacteria inside the fibers was confirmed by fluorescence microscopy and SEM. Although the electrospinning process typically uses harsh organic solvents and extreme conditions that generally are harmful to bacteria, we describe techniques that overcome these limitations. The encapsulated microbes were viable for several months, and their metabolic activity was not affected by immobilization; thus they could be used in various applications. Furthermore, we have engineered a microbe-encapsulated cross-linked fibrous polymeric material that is insoluble. Also, the microbe-encapsulated active matrix permits efficient exchange of nutrients and metabolic products between the microorganism and the environment. The present results demonstrate the potential of the electrospinning technique for the encapsulation and immobilization of bacteria in the form of a synthetic biofilm, while retaining their metabolic activity. This study has wide-ranging implications in the engineering and use of novel bio-hybrid materials or biological thin-film catalysts.

English

A laboratory-scale, four-stage continuous flow reactor system was constructed to test the viability of high-strength acid mine drainage (AMD) and municipal wastewater (MWW) passive co-treatment. Synthetic AMD of pH 2.6 and acidity of 1870 mg/L as CaCO3 equivalent containing a mean 46, 0.25, 2.0, 290, 55, 1.2 and 390 mg/L of Al, As, Cd, Fe, Mn, Pb and Zn, respectively, was mixed at a 1:2 ratio with raw MWW from the City of Norman, Oklahoma and introduced to the system which had a total residence time of 6.6 days. During the 135-d experiment, dissolved Al, As, Cd, Fe, Mn, Pb and Zn concentrations were consistently decreased by 99.8, 87.8, 97.7, 99.8, 13.9, 87.9 and 73.4 %, respectively, pH increased to 6.8 ±0.1, and net-alkaline effluent produced. At a wasting rate of 0.69 % of total influent flow, the system produced sludge with Al, As, Cd, Cr, Cu, Fe, Pb and Zn at least an order of magnitude greater than the theoretical influent mix, which presents a possible environmental liability if not sustainably recovered or disposed. These results indicate that passive co- treatment is a promising approach that can be optimized and applied to improve water quality with minimal use of fossil fuels and refined materials.

English

Passive co-treatment of municipal wastewater and synthetic acid mine drainage in a laboratory-scale, four-stage continuous flow reactor system was examined for changes in fecal indicator bacteria counts. Synthetic acid mine drainage was mixed at a 1:2 ratio with raw municipal wastewater from the City of Norman, Oklahoma and introduced to the system. The municipal wastewater contained varying concentrations of total coliforms (TC), fecal coliforms (FC), E. coli (EC), and fecal streptococci (FS). Initial concentrations ranged from 6-13, 0.6-6, 3-5, and 0.1-0.7 million cfu/100 mL, for TC, FC, EC, and FS, respectively. During the 6.6-day system residence time, a 100% reduction of all indicator bacteria was observed. However, indicator bacteria exhibited evidence of sub- lethal injury with slower colony formation rates on standard growth media. Extending standard incubation periods resulted in higher concentrations of all indicator bacteria in each treatment stage, except the final stage where only EC and TC counts increased. Although this co-treatment regime effectively reduced indicator bacteria concentrations, much remains unknown about the potential for sub-lethal injury to indicator bacteria and its impact on the viability of co- treatment for pathogen removal.

MINERAL TRAPPING OF CO2VIA OIL SHALE ASH AQUEOUS CARBONATION: CONTROLLING MECHANISM OF PROCESS RATE AND DEVELOPMENT OF CONTINUOUS-FLOW REACTOR SYSTEM

-containing gas. As even minute amounts of extraneous substances present in water influence the extent and rate of lime solubility in water, the behavior of lime as the key component of ash in various conditions was studied and the mechanism of process deceleration was proposed. As the next step, a laboratory-scale continuous-flow reactor system for aqueous carbonation of oil shale ash and main considerations for industrial pilot-scale plant design were developed.

Kinetic model for oxygen concentration dependence in the supercritical water oxidation of an industrial wastewater

The objective of this work was the determination of a global rate expression for the kinetics of the supercritical water oxidation (SCWO) of cutting fluid wastes generated in metal industries. SCWO experiments were carried out in a continuous flow reactor system using pure oxygen as the oxidant at a constant pressure of 25 MPa. The temperature effect was studied in the range 673–773 K. Oxygen excess coefficient was varied from n = 0.4 (60% of stoichiometric oxygen) to n = 1.2 (20% oxygen excess) to determine the reaction order for O2. The effectiveness of the process was monitored in terms of COD removal. The rate equation parameters were obtained by fitting of experimental data to the differential equation obtained using the Runge–Kutta algorithm. The kinetic model proposed allows the prediction of the COD conversion with respect to oxygen supply to optimize the operating conditions and to minimize investment and operating costs.

Application of hydrothermal reaction to conversion of plant-origin biomasses into acetic and lactic acids

In this paper, some recent advances in our research on hydrothermal conversion of biomass into useful substances are presented. Here, we mainly focus on the production of acetic acid and lactic acid from carbohydrates including aldose, lignocellulosic biomass, and glycerin along with the discussion of some reaction mechanisms and the interaction between the main components of natural material, such as cellulose and lignin in lignocellulosic biomass. A large-scale continuous flow reactor system was also presented.

Historical Developments in Hydroprocessing Bio-oils

This paper is a review of the developments in the field of catalytic hydroprocessing of biomass-derived liquefaction conversion products (bio-oil) over the past 25 years. Work has been underway, primarily in the U.S. and Europe, in catalytic hydrotreating and hydrocracking of bio-oil in both batch-fed and continuous-flow bench-scale reactor systems. A range of heterogeneous catalyst materials have been tested, including conventional sulfided catalysts developed for petroleum hydroprocessing and precious metal catalysts. The important processing differences have been identified, which required adjustments to conventional hydroprocessing as applied to petroleum feedstocks. This application of hydroprocessing is seen as an extension of petroleum processing and system requirements are not far outside the range of conventional hydroprocessing. The technology is still under development but can play a significant role in supplementing increasingly expensive petroleum.

Selective oxidation of carbohydrates with gold catalysts: Continuous-flow reactor system for glucose oxidation

For the first time, a continuous-flow liquid-phase oxidation using a gold catalyst is described. A 0.25% Au/Al 2O 3 catalyst was investigated in the continuous-flow carbohydrate oxidation using glucose as the model compound. To achieve this, a continuous stirred tank reactor (CSTR) system was developed in which the powdered catalyst was separated by a combination of an ultrasonic separator and a separation vessel. The continuous-flow glucose oxidation was carried out at 40 °C, pH 9 and 1 bar oxygen partial pressure and maintained for 70 days. During this run-time the residence time and glucose concentration were varied. The alumina-supported gold catalyst showed very high activity and selectivity to gluconic acid. The long-term stability of the gold catalyst was excellent as no loss in activity or selectivity occurred during 70 days of continuous operation.

A Continuous-Flow Process for Natural Product Synthesis

A continuous-flow reactor system was designed and used for the synthesis of a neolignan natural product, grossamide (8). The polymer-supported HOBt packed in the column (Reagent 4) was activated by flowing the DMF solution of ferulic acid (1), PyBrOP (2), and DIPEA. After washing the unreacted materials out, the THF solution of amine 3 was flowed into the first column. The output was then directed through the second column containing a sulfonic acid resin (Reagent 5) as a scavenger to afford amide 6 in 90% conversion. Amide 6 was diluted with a solution of hydrogen peroxide urea complex and sodium dihydrogen phosphate buffer in acetone-water. The combined flow was then passed through the third column packed with an immobilized peroxidase on silica (Reagent 7) to give grossamide.

Mycobacterium marinumbiofilm formation reveals cording morphology

Abstract The emergence of the nontuberculosis mycobacteria (NTM) as clinically relevant pathogens has warranted the study of these ubiquitous organisms in the context of their likely environmental niche, the biofilm. We assayed the NTM bacterium Mycobacterium marinum strain 1218R, a fish outbreak isolate, for biofilm formation on different surfaces over time using three different methods. Using the MBEC system, biofilm development occurred continually over the 14-day culture period reaching a mature or stable biofilm state after 7 days postinoculation. Quantification of M. marinum biofilm formation on high-density polyethylene (HDPE), polycarbonate (PC) and silicon (Si) coupons over a 14-day period was evaluated using a continuous flow reactor system. M. marinum developed biofilms on all of the surfaces tested. However, substantially more biofilm accumulated on the silicon than on the other substrates (Si>HDPE>PC) under the same growth conditions indicating that silicon was the most effective substratum studied for the generation of M. marinum biofilms and suggesting a correlation between surface hydrophobicity and attachment. Finally, confocal laser scanning microscopy was used to visualize M. marinum biofilm development in situ over time and revealed an unusual biofilm ultrastructure. Large cell clusters attached to the surface grew in parallel sinuous arrays of cells that formed large cords.

Development of a Continuous-Flow Reactor System for Conversion of Water-Soluble Organics in Supercritical Water under Superhigh Pressure

Development of a Continuous-Flow Reactor System for Conversion of Water-Soluble Organics in Supercritical Water under Superhigh Pressure

Radicals from the Pyrolysis of Tobacco

The fractional pyrolysis of Bright tobacco was studied in an inert nitrogen environment at atmospheric pressure over a temperature range of 200−700 °C, using a continuous-flow reactor system. The effect of pyrolysis conditions on the generation of free radicals and their distribution among total particulate matter (TPM), char residue, and the gas phase was characterized using electron paramagnetic resonance (EPR) and EPR spin-trapping techniques. It was found that the fractional pyrolysis of tobacco led to the generation of free radicals with g-factors of 2.0035−2.0040. They were formed during pyrolysis at temperatures of >380 °C and were present in both char and TPM. The concentration of these radicals in TPM varied from 0 spins/g at 240 °C to 11 × 1016 spins/g of TPM at 620 °C. The concentration of these radicals in the char residue increased as the pyrolysis temperature increased; a maximum concentration of 1.2 × 1019 spins/g of char at 480 °C was obtained, and then the value declined. The g-values of ...

Continuous Electricity Generation from Domestic Wastewater and Organic Substrates in a Flat Plate Microbial Fuel Cell

A microbial fuel cell (MFC) is a device that converts organic matter to electricity using microorganisms as the biocatalyst. Most MFCs contain two electrodes separated into one or two chambers that are operated as a completely mixed reactor. In this study, a flat plate MFC (FPMFC) was designed to operate as a plug flow reactor (no mixing) using a combined electrode/proton exchange membrane (PEM) system. The reactor consisted of a single channel formed between two nonconductive plates that were separated into two halves by the electrode/PEM assembly. Each electrode was placed on an opposite side of the PEM, with the anode facing the chamber containing the liquid phase and the cathode facing a chamber containing only air. Electricity generation using the FPMFC was examined by continuously feeding a solution containing wastewater, or a specific substrate, into the anode chamber. The system was initially acclimated for 1 month using domestic wastewater orwastewater enriched with a specific substrate such as acetate. Average power density using only domestic wastewater was 72+/-1 mW/m2 at a liquid flow rate of 0.39 mL/min [42% COD (chemical oxygen demand) removal, 1.1 h HRT (hydraulic retention time)]. At a longer HRT = 4.0 h, there was 79% COD removal and an average power density of 43+/-1 mW/m2. Power output was found to be a function of wastewater strength according to a Monod-type relationship, with a half-saturation constant of Ks = 461 or 719 mg COD/L. Power generation was sustained at high rates with several organic substrates (all at approximately 1000 mg COD/L), including glucose (212+/-2 mW/ m2), acetate (286+/-3 mW/m2), butyrate (220+/-1 mW/ m2), dextran (150+/-1 mW/m2), and starch (242+/-3 mW/ m2). These results demonstrate the versatility of power generation in a MFC with a variety of organic substrates and show that power can be generated at a high rate in a continuous flow reactor system.

Inhibition of pyrite oxidation by a phospholipid in the presence of silicate.

The influence of sodium silicate on the ability of a diacetylene-containing phospholipid (23:2 diyne PC) to inhibit the oxidation of pyrite at pH 2 and pH 6 was investigated. The phospholipid used has previously been reported to show up to 80% suppression of pyrite oxidation and to show excellent stability down to at least pH 2. Pyrite was leached with a solution containing Fe3+ but no coating agent and three different solutions or treatments: a lipid treatment, a silicate treatment, and a lipid + silicate treatment. Pyrite oxidation was based on iron (Fe3+, Fe2+) leached out of a continuous-flow porous-bed reactor system. The results show that at pH 6 the silicate and lipid both bind strongly to the pyrite surfaces, providing a barrier that inhibits the production and subsequent release of oxidation products. The lipid is superior to the silicate in suppressing pyrite oxidation at both pH 2 and pH 6. Also, the presence of silicates decreased the ability for the lipid to suppress pyrite oxidation, both at pH 2 and pH 6. The reaction mechanism for pyrite oxidation at pH 2 is first order for pyrite leached by solutions containing only ferric, ferric together with silicate, and ferric combined with silicate and lipid. The only treatment that effectively prevented pyrite oxidation at pH 2 was the lipid treatment. The Fe speciation results are supported by both SEM images and EDS calculations.