Influence of Volatile Fatty Acids on Nitrite Accumulation by a Pseudomonas stutzeri Strain Isolated from a Denitrifying Fluidized Bed Reactor

Intermediate nitrite accumulation during denitrification by Pseudomonas stutzeri isolated from a denitrifying fluidized bed reactor was examined in the presence of different volatile fatty acids. Nitrite accumulated when acetate or propionate served as the carbon and electron source but did not accumulate in the presence of butyrate, valerate, or caproate. Nitrite accumulation in the presence of acetate was caused by differences in the rates of nitrate and nitrite reduction and, in addition, by competition between nitrate and nitrite reduction pathways for electrons. Incubation of the cells with butyrate resulted in a slower nitrate reduction rate and a faster nitrite reduction rate than incubation with acetate. Whereas nitrate inhibited the nitrite reduction rate in the presence of acetate, no such inhibition was found in butyrate-supplemented cells. Cytochromes b and c were found to mediate electron transport during nitrate reduction by the cells. Cytochrome c was reduced via a different pathway when nitrite-reducing cells were incubated with acetate than when they were incubated with butyrate. Furthermore, addition of antimycin A to nitrite-reducing cells resulted in partial inhibition of electron transport to cytochrome c in acetate-supplemented cells but not in butyrate-supplemented cells. On the basis of these findings, we propose that differences in intermediate nitrite accumulation are caused by differences in electron flow to nitrate and nitrite reductases during oxidation of either acetate or butyrate.     

Improvement of Process Stability of Microbiological Quinoline Degradation in a Three‐Phase Fluidized Bed Reactor

The biological degradation of quinoline by suspended and immobilized Comamonas acidovorans was studied under continuous and discontinuous operating conditions in a three‐phase fluidized bed reactor. C. acidovorans degrades quinoline into biomass and carbon dioxide. Quinoline and the intermediates of its metabolic pathway are found only by quinoline shockloads. The continuous degradation of quinoline by suspended biomass was only possible, if the dilution rate was less than the growth rate (μ_max =0.42 h^–1) and the concentration of a shockload was less than 1 kg/m³. A concentration greater than 1 kg/m³ led to an irreversible damage of the cells. Hence, two different carrier materials were used for immobilization by attachment, to increase the stability of the process. Using immobilization of biomass on carriers decouples the hydrodynamic retention time and the growth rate of the microorganisms. A comparison of the carrier material showed no differences with respect of activity and stability of the biofilm. The process stability of a three‐phase fluidized bed reactor was increased by immobilized biomass. The degradation of toxic shockloads was only possible with immobilized biomass. A dynamic model has been developed to describe the concentration profile of quinoline, 2‐hydroxyquinoline as metabolite and the suspended biomass. A comparison of the measured and calculated values showed good agreement.     

Biofilm Growth and Bed Fluidization in a Fluidized Bed Reactor Packed with Support Materials of Low Density

Support materials of low‐density for fluidized bed reactors provide several operational advantages, including lower energy requirements and proper biofilm growth balance. The aim of this investigation was to study the extent of biofilm growth and bed fluidization in an experimental reactor, using polyester resin (ρ_pr = 1220 kg/m³) and vitrified expanded perlite (ρ_vep = 1710 kg/m³) as alternative support materials to conventional silica sand. A noteworthy amount of biofilm was observed to be attached to both support materials from the very beginning of the bioreactor operation. Nevertheless, there were significant variations in biofilm growth and activity over the course of the experimental trials. For both perlite and polyester beds, the highest biofilm mass and the highest total number of mesophilic bacteria were observed between the 7^th and the 10^th day, showing a steady state trend at the end of the experimental runs. The chemical oxygen demand (COD) removal levels were concomitant with biofilm mass and total mesophilic bacteria changes, although the polyester bed efficiency was slightly higher than that for the perlite bed. As expected, the polyester bed was fluidized at a lower re‐circulation flow compared to the perlite bed. Reactor back‐washing was not required for these support materials since biomass excess was adequately separated by means of a special internal device. The efficiencies of removal of organic matter achieved were acceptable (up to 78 %) despite the low volume of the support material (25 %) and the low hydraulic retention time (30 min).     

Autohydrogenotrophic Denitrifying Microbial Community in a Glass Beads Biofilm Reactor

A glass bead biofilm reactor was operated using H₂ as an electron donor to remove nitrate at 150 mg NO₃–N l⁻¹ to below detection level. The microbial community in the glass beads biofilm reactor was investigated by using denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis. In DGGE analysis of the biofilm, five bands were dominant and indicated the presence of eight β-proteobacteria, one γ-proteobacteria and twelve clostridia. An unculturable Hydrogenophaga sp., which is a new genus of hydrogen-oxidizing bacterium was dominant in microbial community of the biofilm reactor.     

Fast Pyrolysis Behavior of Banagrass as a Function of Temperature and Volatiles Residence Time in a Fluidized Bed Reactor

A reactor was designed and commissioned to study the fast pyrolysis behavior of banagrass as a function of temperature and volatiles residence time. Four temperatures between 400 and 600°C were examined as well as four residence times between ~1.0 and 10 seconds. Pyrolysis product distributions of bio-oil, char and permanent gases were determined at each reaction condition. The elemental composition of the bio-oils and chars was also assessed. The greatest bio-oil yield was recorded when working at 450°C with a volatiles residence time of 1.4 s, ~37 wt% relative to the dry ash free feedstock (excluding pyrolysis water). The amounts of char (organic fraction) and permanent gases under these conditions are ~4 wt% and 8 wt% respectively. The bio-oil yield stated above is for ''dry'' bio-oil after rotary evaporation to remove solvent, which results in volatiles and pyrolysis water being removed from the bio-oil. The material removed during drying accounts for the remainder of the pyrolysis products. The ''dry'' bio-oil produced under these conditions contains ~56 wt% carbon which is ~40 wt% of the carbon present in the feedstock. The oxygen content of the 450°C, 1.4 s ''dry'' bio-oil is ~38 wt%, which accounts for ~33 wt% of the oxygen in the feedstock. At higher temperature or longer residence time less bio-oil and char is recovered and more gas and light volatiles are produced. Increasing the temperature has a more significant effect on product yields and composition than increasing the volatiles residence time. At 600°C and a volatiles residence time of 1.2 seconds the bio-oil yield is ~21 wt% of the daf feedstock, with a carbon content of 64 wt% of the bio-oil. The bio-oil yield from banagrass is significantly lower than from woody biomass or grasses such as switchgrass or miscanthus, but is similar to barley straw. The reason for the low bio-oil yield from banagrass is thought to be related to its high ash content (8.5 wt% dry basis) and high concentration of alkali and alkali earth metals (totaling ~2.8 wt% relative to the dry feedstock) which are catalytic and increase cracking reactions during pyrolysis.     

Identification and Activities In Situ of Nitrosospira and Nitrospira spp. as Dominant Populations in a Nitrifying Fluidized Bed Reactor

Bacterial aggregates from a chemolithoautotrophic, nitrifying fluidized bed reactor were investigated with microsensors and rRNA-based molecular techniques. The microprofiles of O₂, NH₄⁺, NO₂⁻, and NO₃⁻ demonstrated the occurrence of complete nitrification in the outer 125 μm of the aggregates. The ammonia oxidizers were identified as members of the Nitrosospira group by fluorescence in situ hybridization (FISH). No ammonia- or nitrite-oxidizing bacteria of the genus Nitrosomonas or Nitrobacter, respectively, could be detected by FISH. To identify the nitrite oxidizers, a 16S ribosomal DNA clone library was constructed and screened by denaturing gradient gel electrophoresis and selected clones were sequenced. The organisms represented by these sequences formed two phylogenetically distinct clusters affiliated with the nitrite oxidizer Nitrospira moscoviensis. 16S rRNA-targeted oligonucleotide probes were designed for in situ detection of these organisms. FISH analysis showed that the dominant populations of Nitrospira spp. and Nitrosospira spp. formed separate, dense clusters which were in contact with each other and occurred throughout the aggregate. A second, smaller, morphologically and genetically different population of Nitrospira spp. was restricted to the outer nitrifying zones.     

Monitoring Fluidized Bed Drying of Pharmaceutical Granules

Placebo granules consisting of lactose monohydrate, corn starch, and polyvinylpyrrolidone were prepared using de-ionized water in a high-shear mixer and dried in a conical fluidized bed dryer at various superficial gas velocities. Acoustic, vibration, and pressure data obtained over the course of drying was analyzed using various statistical, frequency, fractal, and chaos techniques. Traditional monitoring methods were also used for reference. Analysis of the vibration data showed that the acceleration levels decreased during drying and reached a plateau once the granules had reached a final moisture content of 1–2 wt.%; this plateau did not differ significantly between superficial gas velocities, indicating a potential criterion to support drying endpoint identification. Acoustic emissions could not reliably identify the drying endpoint. However, high kurtosis values of acoustic emissions measured in the filtered air exhaust corresponded to high entrainment rates. This could be used for process control to adjust the fluidization gas velocity to allow drying to continue rapidly while minimizing entrainment and possible product losses.     

Fluidized Bed Hot-Melt Granulation as a Tool to Improve Curcuminoid Solubility

Curcumin is the main bioactive component of Curcuma longa L. and has recently aroused growing interest from the scientific community. Unfortunately, the medicinal properties attributed to curcuminoids are impaired by their low oral bioavailability or low solubility in aqueous solutions. Many strategies have been studied to improve curcumin solubility; however, the preparation of granules using hydrophilic materials has never been attempted. The aim of this work was to develop curcumin granules by fluidized bed hot-melt granulation using the hydrophilic carrier Gelucire® 50:13. A two-level factorial design was used to verify the influence of Gelucire® 50:13 and lactose contents found in the granules on their size, morphology, bulk and tapped densities, flow, moisture content, and water activity. The granules obtained were also evaluated by differential scanning calorimetry, thermogravimetric analysis, X-ray powder diffraction, and infrared spectrometry. The curcumin solubility and dissolution rates in water were determined by liquid chromatography. The best formulation provides an increase of curcumin solubility of 4642-fold and 3.8-fold compared to the physical mixture. The dissolution tests showed a maximum drug release from granules after 45 min of 70% at pH 1.2 and 80% at pH 5.8 and 7.4, while for non-granulated curcumin, the release was below 20% in all pH. The solid-state characterization and solubility measurement showed good stability of granules over 9 months. The results attest that the fluidized bed hot-melt granulation with hydrophilic binders is an attractive and promising alternative to obtain solid forms of curcumin with enhanced bioavailability.     

Denitrification Performance of Pseudomonas denitrificans in a Fluidized‐Bed Biofilm Reactor and in a Stirred Tank Reactor

Denitrification of a synthetic wastewater containing nitrates and methanol as carbon source was carried out in two systems – a fluidized‐bed biofilm reactor (FBBR) and a stirred tank reactor (STR) – using Pseudomonas denitrificans over a period of five months. Nitrogen loading was varied during operation of both reactors to assess differences in the response to transient conditions. Experimental data were analyzed to obtain a comparison of denitrification kinetics in biofilm and suspended growth reactors. The comparison showed that the volumetric degradation capacity in the FBBR (5.36 kg _N · m^–3 · d^–1) was higher than in the STR, due to higher biomass concentration (10 kg _BM · m^–3 vs 1.2 kg _BM m^–3).     

Bioremediation of Perchlorate-Contaminated Groundwater Using a Packed Bed Biological Reactor

The objective of this study was to assess the efficacy of a bench-scale, acetate-fed, packed bed bioreactor (PBR) to treat low concentrations (>1 mg L^?1) of perchlorate (ClO₄ ^?) in groundwater collected from an impacted site. The PBR consisted of a cylindrical plexiglass column packed with Celite, a diatomaceous earth product, as a solid support medium. The reactor was inoculated with a ClO_?4 ^?-reducing bacterial isolate, perclace. Results showed that with influent ClO₄ ^? concentrations of approximately 800 μg L^?1, nondetectable effluent concentrations (>4 μg L^?1) were achieved with the PBR/perclace system at residence time as low as 0.3 h. Influent acetate concentrations of less than 500 mg L^?1 yielded nondetectable effluent ClO^? ₄ concentrations, and acetate concentrations generally less than 50 mg L^?1 were present in the effluent. Nitrate (NO^? _?3) was also removed in this system, while sulfate (SO₄ ^2?) reduction was not observed. The pH remained relatively constant during the process.     

Monitoring Granulation Rate Processes Using Three PAT Tools in a Pilot-Scale Fluidized Bed

The purpose of this research was to analyze and compare the responses of three Process Analytical Technology (PAT) techniques applied simultaneously to monitor a pilot-scale fluidized bed granulation process. Real-time measurements using focused beam reflectance measurement (Lasentec FBRM) and near-infra red spectroscopy (Bruker NIR) were taken by inserting in-line probes into the fluidized bed. Non-intrusive acoustic emission measurements (Physical Acoustic AE) were performed by attaching piezoelectric sensors on the external wall of the fluidized bed. Powder samples were collected at regular intervals during the granulation process and characterized offline using laser diffraction, scanning electron microscopy, stereo-optical microscopy and loss on drying method. PAT data comprising chord length distribution and chord count (from FBRM), absorption spectra (from NIR) and average signal levels and counts (from AE) were compared with the particle properties measured using offline samples. All three PAT techniques were able to detect the three granulation regimes or rate processes (wetting and nucleation, consolidation and growth, breakage) to varying degrees of sensitivity. Being dependent on optical signals, the sensitivities of the FBRM and NIR techniques were susceptible to fouling on probe windows. The AE technique was sensitive to background fluidizing air flows and external interferences. The sensitivity, strengths and weaknesses of the PAT techniques examined may facilitate the selection of suitable PAT tools for process development and scale-up studies.     

Experimental Investigation of Drying Behavior of Carrots in a Fluidized Bed with Energy Carrier

A pilot scale fluidized bed dryer with inert particles as energy carrier was used to investigate the drying characteristics of carrot in this type of dryer. Glass beads, hollow steel balls and pieces of dry carrot were used as inert materials. The effects of sample diameter, inert material type, inert material diameter, amount of inert material, air velocity and temperature on the rate of drying were studied. It was found that the presence of inert particles enhances the rate of drying. The results of this study also revealed that, although the rate of drying increased with decreasing sample diameter, increasing of inert material thermal conductivity, and increasing of air temperature, but the inert material diameter and air velocity did not have any significant effect on the rate of drying. The independence of the rate of drying on air velocity in well fluidized systems, indicates that external diffusion is not the controlling step in this process. It was also found that the presence of inert materials caused the drying material to reach its final internal temperature more rapidly. The internal temperature of the drying material, also increased with increasing diameter and thermal conductivity of the inert materials.     

Presence of Two Different Active nirS Nitrite Reductase Genes in a Denitrifying Thauera sp. from a High-Nitrate-Removal-Rate Reactor

The nirS nitrite reductase genes were studied in two strains (strains 27 and 28) isolated from two denitrifying reactors and characterized as Thauera according to their 16S rRNA gene sequences. Strain 28 contains a single nirS sequence, which is related to the nirS of Thauera mechernichensis, and strain 27 contains two nirS sequences; one is similar to the nirS sequence from Thauera mechernichensis (gene 2), but the second one (gene 8) is from a separate clade with nirS from Pseudomonas stutzeri, Azoarcus species, Alcaligenes faecalis, and other Thauera species. Both genes were expressed, but gene 8 was constitutively expressed while gene 2 was positively regulated by nitrate.     

三相逆流湍动床气液传质性能的研究

由空气-水(清水/废水)-中空玻璃珠构成三相体系,在表观气速0·53~10mm·s-1、固含率为0~0·3、表观液速0~0·2mm·s-1的条件下,采用溶氧仪研究了三相逆流湍动床的气液传质性能,考察了操作参数和液体性质对液相容积传质系数kLa的影响。结果表明,在所试条件下,kLa为0·0456~1·414min-1。kLa随着表观气速和表观液速的增加而增加,随着固含率的增加先增加后减小,0·05~0·08为反应器传质的最优固含率条件。液体性质对kLa有重大影响,高浓度模拟废水和工业废水中的kLa比清水中的kLa分别减小39·0%和50·9%。研究结果可为后续逆流湍动床废水生物处理过程分析与模拟提供传质基础数据。     

Investigation on Side-Spray Fluidized Bed Granulation with Swirling Airflow

Top-spray fluidized bed granulation with axial fluidization airflow from the bottom of the granulator is well-established in the pharmaceutical industry. The application of swirling airflow for fluidized bed granulation was more recently introduced. This study examined the effects of various process parameters on the granules produced by side-spray fluidized bed with swirling airflow using the central composite and Box–Behnken design of experiment. Influence of the amount of binder solution, spray rate, and distance between spray nozzle and powder bed were initially studied to establish operationally viable values for these parameters. This was followed by an in-depth investigation on the effects of inlet airflow rate, atomizing air pressure and distance between spray nozzle and powder bed on granule properties. It was found that the amount of binder solution had a positive correlation with granule size and percentage of lumps but a negative correlation with size distribution and Hausner ratio of the granules. Binder solution spray rate was also found to affect the granules size. High drug content uniformity was observed in all the batches of granules produced. Both inlet airflow rate and atomizing air pressure were found to correlate negatively with granule size and percentage of lumps but correlate positively with the size distribution of the granule produced. Percentage of fines was found to be significantly affected by inlet airflow rate. Distance between spray nozzle and powder bed generally affected the percentage of lumps.     

三相流化床中固定化米根霉萃取发酵生产L-乳酸

以TRPO／磺化煤油为萃取剂,在2L三相流床反应器中进行了固定化米根霉原位萃取和异位萃取发酵生产L-乳酸的实验,结果表明,发酵液中的pH值能被控制在3．5左右．产酸速率高达每小时．每1L固定化颗粒产生11gL-乳酸。提出了一个数学模型用以描述萃取发酵中L-乳酸的积累及在各相的分配情况。模型计算曲线与实验值符合良好。     

Development and Application of a Process Window for Achieving High-Quality Coating in a Fluidized Bed Coating Process

Next to the coating formulation, process conditions play important roles in determining coating quality. This study aims to develop an operational window that separates layering from agglomeration regimes and, furthermore, the one that leads to the best coating quality in a fluidized bed coater. The bed relative humidity and the droplet size of the coating aerosol were predicted using a set of engineering models. The coating quality was characterized using a quantitative image analysis method, which measures the coating thickness distribution, the total porosity, and the pore size in the coating. The layering regime can be achieved by performing the coating process at a certain excess of the viscous Stokes number (ΔSt _v). This excess is dependent on the given bed relative humidity and droplet size. The higher the bed relative humidity, the higher is the ΔSt _v required to keep the process in the layering regime. Further, it is shown that using bed relative humidity and droplet size alone is not enough to obtain constant coating quality. The changes in bed relative humidity and droplet size have been identified to correlate to the fractional area of particles sprayed per unit of time. This parameter can effectively serve as an additional parameter to be considered for a better control on the coating quality. High coating quality is shown to be achieved by performing the process close to saturation and spraying droplets small enough to obtain high spraying rate, but not too small to cause incomplete coverage of the core particles.     

Continuous Solvent/Detergent Virus Inactivation Using a Packed‐Bed Reactor

Continuous virus inactivation (VI) remains one of the missing pieces while the biopharma industry moves toward continuous manufacturing. The challenges of adapting VI to the continuous operation are two‐fold: 1) achieving fluid homogeneity and 2) a narrow residence time distribution (RTD) for fluid incubation. To address these challenges, a dynamic active in‐line mixer and a packed‐bed continuous virus inactivation reactor (CVIR) are implemented, which act as a narrow RTD incubation chamber. The developed concept is applied using solvent/detergent (S/D) treatment for inactivation of two commonly used model viruses. The in‐line mixer is characterized and enables mixing of the viscous S/D chemicals to ±1.0% of the target concentration in a small dead volume. The reactor's RTD is characterized and additional control experiments confirm that the VI is due to the S/D action and not induced by system components. The CVIR setup achieves steady state rapidly before two reactor volumes and the logarithmic reduction values of the continuous inactivation process are identical to those obtained by the traditional batch operation. The packed‐bed reactor for continuous VI unites fully continuous processing with very low‐pressure drop and scalability.     

内循环颗粒污泥床硝化反应器流动模型研究

采用脉冲刺激响应技术,对稳态内循环颗粒污泥床硝化反应器进行了示踪试验。根据试验结果,分别运用轴向扩散模型和多釜全混流反应器串联模型,对反应器沉淀区和循环区的流态进行了分析和判断。结果表明,反应器沉淀区的分散数D/uL为0.00148,该区域的流态接近于平推流反应器（PFR）;反应器循环区的串联级数为1.021,该区域的流态接近于全混流反应器（CSTR）。稳态时,反应器的理论水力停留时间为360min,实际水力停留时间为341.2min,反应器中死区所占的体积百分比为5.22％,其中生物体死区为0.75%,水力死区为4.47%,表明反应器结构性能良好。根据试验和分析结果,建立了内循环颗粒污泥床硝化反应器的流动模型,即全混流和平推流的串联组合模型。由流动模型所得的理论停留时间分布曲线与由试验所得的实际停留时间分布曲线吻合良好,两者的平均相对误差为8.56%,表明所建模型具有较高的准确性。