Free Cell System Research Articles

Pharmacokinetics and biodistribution of negatively charged pectin nanoparticles encapsulating paclitaxel.

Pectin, a naturally occurring biopolymer has been found to have increasing applications in the pharmaceutical and biotechnology industry. Sugars with their three-dimensional structures are important for many biological functions. We report preparation of negatively charged pectin nanoparticles encapsulating paclitaxel, a broad-spectrum anticancer drug for possible therapeutic applications. The mean diameter of the nanoparticles was ~300–350 nm with an encapsulation efficiency ~17 %. The TEM studies indicated that the particles were spherical in shape and their sizes are in unison with the DLS size spectra. The surface charge of pectin polymer was −5 mV and of nanoparticles were ~ −32 mV. The enhanced surface charge shows greater stability. The high electrophoretic mobility of ~3.5 to 1.5 μmcm/Vs confirmed the nano-size of particles. We compared the cytotoxic effect of paclitaxel (Pax) per se, pectin nanoparticles (PPN), and pectin chains on Hep G2, hepatic carcinoma cell line. Dose-dependent cytotoxicity was observed, wherein ~21.7 ± 3.2 % cytotoxicity was observed by PPN, but Pax per se showed ~55.6 ± 3.5 % cytotoxicity in a 72-h assay. The pharmacokinetics and biodistribution studies on Balb/c mice indicated that the nanoparticles had prolonged plasma retention of the drug with major accumulation in liver tissue after an i.v. tail vein injection of 20 mg/kg drug. The rank order of concentration are as follows, i.e., liver > kidney > lung > spleen for the PPN and spleen > liver > kidney ≥ lung for Pax per se. The in vitro studies clearly indicated that the efficacy of the drug was not compromised by encapsulation, making it a good candidate to deliver biopharmaceuticals. Nanoparticles produced free radicals in the free cell system and this ability caused oxidative stress, which may give rise to inflammation, cell destruction, and genotoxicity. Thus, the results obtained in this study holds great promise for pectin nanoparticles to be exploited for passive delivery of paclitaxel to tumor tissues, in particular, liver cancers.

Immobilisation of Clostridium spp. for production of solvents and organic acids

AbstractThis review summarises the high potential of immobilised cells systems for the fermentative production of compounds, mainly produced by representatives of the Clostridium genus. Microorganisms of Clostridium species are recognised as good producers of a wide range of chemicals in almost every sector of industry. The combination of this microorganism with its immobilisation opens up new possibilities and renders the fermentation process more sophisticated than in a free-cell system. This review provides a comprehensive summary of techniques used in immobilisation of Clostridium species with regard to specific products and types of fermentation. In addition, comparisons of particular types of immobilisation techniques used in fermentation processes are summarised by specific products.

4’-Aminochalcones As Novel Inhibitors of the Chlorinating Activity of Myeloperoxidase

The excessive activation of neutrophils generates reactive oxygen species (ROS) and the secretion of primary granular enzymes, such as myeloperoxidase (MPO), which is implicated in numerous inflammatory diseases. The aim of this study was to evaluate chalcones as inhibitors of the chlorinating activity of MPO using in vitro and ex vivo assays. In addition to cytotoxic properties, the inhibition of respiratory burst, the scavenger capacity, and the oxidation potential were measured. 4'-Aminochalcone (1), 4'-amino-4- fluorochalcone (2), and 4'-amino-4-methylchalcone (3) exhibited potent inhibition of the chlorinating activity of MPO, as evaluated in a neutrophil system and a free cell system, to the following degree: (1) IC50 = 0.265 � 0.036 μmol L-1; (2) IC50 = 0.250 � 0.081 μmol L-1; and (3) IC50 = 0.250 � 0.012 μmol L-1. These values were similar to those for 5-fluorotryptamine (IC50 = 0.192 � 0.012 μmol L-1), a compound considered to be a potent MPO inhibitor. These aminochalcones were not toxic to neutrophils at concentrations below 100 μmol L- 1, as determined by the trypan blue exclusion assay. Compounds 1-3 presented a high oxidation potential (Epa1 ≉ 0.80 V), low scavenger capacity against DPPH• and HOCl, and low inhibition of respiratory burst. These data indicated that aminochalcones are potent inhibitors of MPO chlorinating activity, a new property for chalcone derivatives, given that they are neither antioxidant agents nor inhibitors of respiratory burst. In conclusion, the selected aminochalcones have potential as pharmacological agents for inflammatory diseases.

Entrapped cell system for decentralized hospital wastewater treatment: inhibitory effect of disinfectants

This study aims to improve decentralized hospital wastewater treatment inhibited by disinfectants by using calcium alginate cell entrapment technique. The effects of disinfectant types (glutaraldehyde, povidone iodine (PI) and a potassium hydroxide solution) and disinfectant concentrations, cell entrapment conditions (cell-to-matrix ratios) and cell loadings were investigated. The batch experiments were conducted using synthetic wastewater with initial chemical oxygen demand (COD) of approximately 370 mg/L and acclimated activated sludge. Among three disinfectants, PI substantially affected the wastewater treatment efficiency (inhibition of 40%) while other disinfectants exhibited inhibition effects of less than 9%. The results also indicated that the entrapped cells obviously performed better than the free cells. The cell-to-matrix ratio of 1:20 (v/v) provided the highest treatment efficiency of 86% (inhibition of 9%) while the free cell system had inhibition of 47%. The system at the entrapped cell loading of 2000 mg/L performed the highest COD removal of 62% for ten-cycle sequencing batch operation. A scanning electron microscope image provided information on entrapped cell structure subjected to the disinfectant.

THE STUDY OF THE INFLUENCE OF TEMPERATURE AND INITIAL GLUCOSE CONCENTRATION ON THE FERMENTATION PROCESS IN THE PRESENCE OF Saccharomyces cerevisiae YEAST STRAIN IMMOBILIZED ON STARCH GELS BY REVERSED-FLOW GAS CHROMATOGRAPHY

The technique of reversed-flow gas chromatography (RFGC) was employed for the determination of the alcoholic fermentation phases and of kinetic parameters for free and immobilized cell systems, at different initial glucose concentrations and temperature values. In addition to this, due to its considerable advantages over other techniques, RFGC was used for the characterization of a new biocatalyst, yeast cells immobilized on starch gel, and especially wheat starch gel. Immobilization of wine yeast Saccharomyces cerevisiae AXAZ-1 was accomplished on wheat and corn starch gels in order to prepare new biocatalysts with great interest for the fermentation industry. The RFGC led with great accuracy, resulting from a literature review, to the determination of reaction rate constants and activation energies at each phase of the fermentation processes. A maximum value of rate constants was observed at initial glucose concentration of 205 g/L, where a higher number of yeast cells was observed. The increase of glucose concentrations had a negative influence on the growth of AXAZ-1 cells and rate constants were decreased. The decrease of fermentation temperature caused a substantial reduction in the viability of immobilized cells as well as in rate constant values. Activation energies of corn starch gel presented lower values than those of wheat starch gel. However, the two supports showed higher catalytic efficiency than free cell systems, proving that starch gels may act as a promoter of the catalytic activity of the yeast cells involved in the fermentation process.

Biodegradation of Crude Oil in Contaminated Soils by Free and Immobilized Microorganisms

The efficiencies of free and immobilized bacterial cultures of petroleum hydrocarbon degraders were evaluated and compared in this study. Hydrocarbon-degrading microbial communities with high tolerance to and high degrading ability of crude oil were obtained from the soil contaminated with crude oil in the Yellow River Delta. Then, the microbial cells were immobilized in sodium alginate (SA) beads and sodium alginate-diatomite (SAD) beads. The biodegradation of crude oil in soil by immobilized cells was compared with that by free cells at three inoculation concentrations, 1 × 104 colony forming units (cfu) kg−1 (low concentration, L), 5 × 104 cfu kg−1 (medium concentration, M), and 1 × 105 cfu kg−1 (high concentration, H). At 20 d after inoculation, the maximum degradation rate in the immobilized systems reached 29.8% (SAD-M), significantly higher (P < 0.05) than that of the free cells (21.1%), and the SAD beads showed greater degradation than the SA beads. Moreover, both microbial populations and total microbial activity reached significantly higher level (P < 0.05) in the immobilized systems than free cell systems at a same initial inoculation amount. The scanning electronic microscope (SEM) images also confirmed the advantages of the immobilized microstructure of SAD beads. The enhanced degradation and bacterial growth in the SAD beads indicated the high potential of SAD beads as an effective option for bioremediation of crude oil-contaminated soils in the Yellow River Delta.

Biodegradation of Phenol by Ralstonia eutropha in a Kissiris‐Immobilized Cell Bioreactor

This study examined the biodegradation of phenol by Ralstonia eutropha in a Kissiris-immobilized cell bioreactor (ICB), operated in a repeated batch recycling mode. The steady biodegradation rate of 23.7 mg/g/h, over a wide range of the initial phenol concentrations up to 1400 mg/L in the ICB, indicated an increased tolerance limit of the Kissiris-immobilized cells towards phenol. Both Haldane and Luong substrate inhibition models were used to describe biodegradation kinetic of free cells system. The Haldane equation gave the following values for the biokinetic parameters: micro(max) = 0.36 h(-1), Ks = 40.48 mg/L, and Ki = 181.9 mg/L. However, according to the Luong model, these parameters were micromax) = 0.23 h(-1), Ks = 24.8 mg/L, Sm = 1018 mg/L, and n = 1.3. By following appropriate operational conditions and use of the ICB, it was found to be possible to extend the efficiency of the highly porous structure of the siliceous mineral Kissiris in cell immobilization. This holds significant promise for pollutant biodegradation issues.

Efficient production of l-lactic acid from hydrolysate of Jerusalem artichoke with immobilized cells of Lactococcus lactis in fibrous bed bioreactors

Hydrolysate of Jerusalem artichoke was applied for the production of l-lactic acid by immobilized Lactococcus lactis cells in a fibrous bed bioreactor system. Preliminary experiments had indicated that the high quality hydrolysate, which was derived from the 40min acid treatment at 95°C and pH 1.8, was sufficient to support the cell growth and synthesis of l-lactic acid. With the addition of 5g/l yeast extract, the fermentative performance of free cell system was evidently improved. After the basal settlement of hydrolysate based fermentation, the batch mode and the fed-batch mode fermentation were carried out in the free cell system and the fibrous bed bioreactor system, respectively. In all cases the immobilized cells presented the superior ability to produce l-lactic acid. The comparison of batch mode and fed-batch mode also indicated that the growth-limiting feeding strategy could reduce the lag phase of fermentation process and enhance the production of l-lactic acid. The achieved maximum concentration of l-lactic acid was 142g/l in the fed-batch mode. Subsequent repeated-batch fermentation of the fibrous bed bioreactor system had further exhibited the persistence and stability of this system for the high production of l-lactic acid in a long term. Our work suggested the great potential of the fibrous bed bioreactor system and hydrolysate of J. artichoke in the economical production of l-lactic acid at industrial scale.

Removal of Cu(II), Co(II) and Fe(III) Ions from Ternary Solution by Free and Entrapped in PVA-Hydrogel Biomass of Penicillium Cyclopium

ABSTRACTBatch sorption equilibrium experiments using free and immobilized Penicillium cyclopium biomass in PVA-hydrogel were carried out using ternary mixture of corresponding metal ion solutions. The metal binding ability of the hybrid hydrogel for Cu(II), Co(II) and Fe(III) ions was determined by atomic absorption spectrophotometer. The performance of free and immobilized biosorbent was evaluated by sorption kinetics and sorption capacities for different metal ions in the mixture. The immobilized system showed higher removal efficiency (expressed as mg metal ions removed per mg metal ions added) in comparison to the free-cell system. In addition, the immobilized system showed two-fold shorter time for reaching the equilibrium in comparison to the free cells. The pseudo-second order kinetic model was applied to the multi-component experimental data and important kinetic parameters of the biosorption process were calculated. The data obtained are in agreement with the assumption that the external mass transfer limitation in the immobilized system can be neglected and biosorption is chemisorption controlled. The immobilized system of organic polymer with entrapped fungal biomass showed high biosorption performance and may be used successfully for the removal of Cu(II), Co(II) and Fe(III) ions from ternary mixed solutions.

Fermented Rice Noodle Wastewater Treatment and Ethanol Production Potential Using Entrapped Yeast Cells

Fermented rice noodle is a major source of food industry generating highly complex organic content (starch) wastewater. This study investigated the treatment of fermented rice noodle wastewater using calcium alginate entrapped yeast cells compared to the free cells. The treatment includes a two-step process: acid hydrolysis for breaking down starch to glucose and fermentation for degrading glucose to ethanol. Yeast culture, Saccharomyces cerevisiae, was used in this study. The experiment was conducted to examine optimum acid concentration and cell entrapment condition for fermentation. Sulfuric acid concentrations ranged from 0.25 to 1.00% by volume were tested while the cells entrapped in calcium alginate at cell-to-matrix (alginate) ratios (by volume) of 1:5, 1:10, and 1:20 were varied. The result showed that the optimum acid concentration of 1.00% provided 5-time higher glucose concentration compared to that in raw wastewater. After the batch fermentation, the entrapped cells reduced total chemical oxygen demand (COD) by 33-46% and glucose concentration by 88-90% while the free cells cannot obviously remove COD and reduced glucose concentration by 62%. The entrapped cells at the cell-to-matrix ratio of 1:5 achieved the best glucose biotransformation performance. The treatment reaction followed second-order kinetics. The entrapped and free cell systems gave the treatments with kinetic constants of 0.007 to 0.010 and 0.001 L/mg/hr, respectively. The entrapped and free yeast cell system potentially produced ethanol of 643 to 801 mg/L.

Hydrolysis of milk lactose in a packed bed reactor system using immobilized yeast cells

AbstractBACKGROUND: Hydrolysis of lactose with β‐D‐galactosidase is one of the most promising biotechnological applications in the food industry because of its use in the production of low lactose milk products and whey hydrolysis. To overcome the problem of enzyme extraction from cells due to the intracellular nature of β‐D‐galactosidase and the poor permeability of the cell membrane to lactose, permeabilization of yeast cells was investigated. Permeabilized whole cells have been claimed to have an advantage over more pure enzyme preparations. In view of the advantages of immobilized cell systems over free cell systems, permeabilized cells were immobilized by an entrapment method in calcium alginate gel. A packed bed reactor together with this immobilized cell system has been used for hydrolysis of milk lactose in a continuous system.RESULTS: Different process parameters (temperature, substrate feed rate, biomass load and time‐course) were optimized to maximize lactose hydrolysis. The immobilized yeast cells (300 mg dry wt) resulted in 87.2% hydrolysis of milk lactose at 30 °C and flow rate 7 mL h−1 in a packed bed reactor system.CONCLUSION: This convenient and relatively inexpensive method of immobilization, resulting in high hydrolysis potential in a continuous system, indicates that permeabilized yeast cells have the potential for the production of low lactose milk and milk products. Copyright © 2010 Society of Chemical Industry

Production of bioethanol from corn meal hydrolyzates by free and immobilized cells of Saccharomyces cerevisiae var. ellipsoideus

The ethanol fermentation of enzymatically obtained corn meal hydrolyzates by free and immobilized Saccharomyces cerevisiae var. ellipsoideus yeast in a batch system was studied. The initial glucose and inoculum concentration and the time required for the efficient ethanol production were optimized taking into account parameters such as ethanol concentration, ethanol yield and volumetric productivity. The yeast cells were immobilized in Ca-alginate by electrostatic droplet generation method. An optimal initial inoculum concentration of 2% (v v−1) and optimal fermentation time of 38 h for both immobilized and free yeasts were determined. Optimal initial glucose concentrations of 150 and 176 g l−1 for free and immobilized system were achieved, respectively. The immobilized cell system was superior to the free cell system since higher ethanol tolerance and productivity and lower substrate inhibition were detected.

Population Yields and Vegetable Juice Fermentation of Leuconostoc mesenteroides Cultures Grown Under Free-Cell or Immobilized-Cell Technologies

Leuconostoc mesenteroides BLAC cultures were produced using classical free-cell fermentation technology and immobilized cell technology (ICT). The ICT process consisted of entrapping the culture into alginate or pectin beads, adding them to a growth medium, and incubating for 14 h to allow growth of the culture inside the beads. Cell populations, survival to freeze-drying and specific acidifying activity (SAA) following inoculation in vegetable juices were examined. In free cell fermentations, 1.3 × 1010 cells/mL were obtained while 1.6 to 2.0 × 1011 cells/g were found in beads. The total cell counts recovered per fermentor were similar in free-cell and ICT systems. In the ICT process, the free-cell level was only of 1% or less. No difference in population yields were noted between alginate and pectin gels. Survival to freeze-drying was between 65 and 80% and was not significantly affected by the prior fermentation process nor the alginate or pectin matrix. A methodology was developed to ascertain the free-cell content of the freeze-dried ICT cultures, and data showed that they contained 97.5% of gel-entrapped cells. Freshly prepared free-cell suspensions had four times higher SAA than comparative free-cell freeze-dried cultures. The dried ICT cultures had lower SAA than free-cell equivalents, but there was no significant effect of the ICT matrix (alginate or pectin) on SAA. The powders of the ICT culture were ground and sieved to obtain particles ranging from 38 μm to 1000 μm in diameter. The smaller the particle, the higher was its SAA. Fermentation of vegetable juices or pastes were carried out with the free and ICT cultures. In the ICT fermentation, the free-cell content of the inoculum represented 2.5% of the total population, but this increased to 88% after the 22 h incubation in vegetable juice. Data are discussed in relationship with potential benefits of ICT cultures in vegetable fermentations.

Biodegradation of propionitrile by Klebsiella oxytoca immobilized in alginate and cellulose triacetate gel

A microbial process for the degradation of propionitrile by Klebsiella oxytoca was studied. The microorganism, K. oxytoca, was isolated from the discharged wastewater of metal plating factory in southern Taiwan and adapted for propionitrile biodegradation. The free and immobilized cells of K. oxytoca were then examined for their capabilities on degrading propionitrile under various conditions. Alginate (AL) and cellulose triacetate (CT) techniques were applied for the preparation of immobilized cells. The efficiency and produced metabolic intermediates and end-products of propionitrile degradation were monitored in bath and continuous bioreactor experiments. Results reveal that up to 100 and 150 mM of propionitrile could be removed completely by the free and immobilized cell systems, respectively. Furthermore, both immobilized cell systems show higher removal efficiencies in wider ranges of temperature (20–40 °C) and pH (6–8) compared with the free cell system. Results also indicate that immobilized cell system could support a higher cell density to enhance the removal efficiency of propionitrile. Immobilized cells were reused in five consecutive degradation experiments, and up to 99% of propionitrile degradation was observed in each batch test. This suggests that the activity of immobilized cells can be maintained and reused throughout different propionitrile degradation processes. A two-step pathway was observed for the biodegradation of propionitrile. Propionamide was first produced followed by propionic acid and ammonia. Results suggest that nitrile hydratase and amidase were involved in the degradation pathways of K. oxytoca. In the continuous bioreactor, both immobilized cells were capable of removing 150 mM of propionitriles completely within 16 h, and the maximum propionitriles removal rates using AL and CT immobilized beads were 5.04 and 4.98 mM h −1, respectively. Comparing the removal rates obtained from batch experiments with immobilized cells (AL and CT were 1.57 and 2.18 mM h −1 at 150 mM of propionitrile, respectively), the continuous-flow bioreactor show higher potential for practical application.

Growth and nutrient removal in free and immobilized green algae in batch and semi-continuous cultures treating real wastewater

Two species of microalgae growing as immobilized and free-cells were compared to test its ability to remove N and P in batch cultures of urban wastewater. The best microalgae-cell growth configuration was selected to be tested in bioreactor operated in semi-continuous mode. Scenedesmus obliquus showed a higher N and P uptake rate in urban wastewater than Chlorella vulgaris. When tested in semi-continuous mode and with the re-calcification of beads, S. obliquus was more effective in removing N and P for longer periods (181 h) than batch cultures; fecal coliforms removal was good (95%) although the final concentration was still unsuitable for discharge to natural water bodies. Protein and lipids content analysis suggest that, from a practical point of view, immobilized systems could facilitate the separation of the biomass from the treated wastewater although in terms of nutritional value of the biomass, immobilized systems do not represent an advantage over free-cell systems.

A feasibility study of immobilized and free mixed culture bioaugmentation for treating atrazine in infiltrate

A feasibility study of phosphorylated-polyvinyl alcohol immobilized and free mixed bacterial culture bioaugmentation for removing atrazine in agricultural infiltrate was conducted utilizing a sand column setup. The effects of bacterial cell loading and infiltration rate on atrazine degradation were investigated by short-term tests in which the amount of synthetic infiltrate fed through was five times of the void volume (five pore volumes) of the sand column. In addition, the loss of the inoculated atrazine-degrading cultures and the change of bacterial community were determined. Selected tests were continued for monitoring a long-term performance of the system (50 pore volumes of the sand column). The results indicated that the inoculated cells removed 42–80% of the atrazine. The infiltration rate and cell loading significantly affected the atrazine removal. In the short-term tests, the immobilized and free cells provided similar atrazine removal; however, leaching of the free cells was much greater than that of the immobilized cells. For the long-term performance, only the immobilized cells provided consistent atrazine removal efficiency throughout the test. Both immobilized and free cell systems exhibited a significant change in bacterial community structure during the atrazine degradation experiments. The infiltration rate was a significant factor for the change.

Fructooligosaccharides and β-fructofuranosidase production by Aspergillus japonicus immobilized on lignocellulosic materials

This work describes the fructooligosaccharides (FOS) and β-fructofuranosidase (FFase) production from sucrose (200 g/l) by Aspergillus japonicus ATCC 20236 immobilized on different lignocellulosic materials including brewer's spent grain, wheat straw, corn cobs, coffee husks, cork oak, and loofa sponge. Transfructosylating (U t) and hydrolyzing (U h) activities of FFase were also determined. The FOS production and FFase activity ranged from 128.35 to 138.73 g/l, and 26.83 to 44.81 U/ml, respectively, for cells immobilized in the different carriers. Corn cobs was the best support material since gave the highest results of microorganism immobilization (1.49 g/g carrier), FOS and FFase production, with FOS productivity (6.61 g/l h) and yield (0.66 g/g based on total substrate; 0.73 g/g based on consumed substrate) higher than those obtained by free cells system. Moreover, the ratio U t/U h of FFase, parameter of importance for elevated FOS production, was greater for cells immobilized in corn cobs than for free cells. Such results demonstrated that corn cobs can be successfully used as carrier for immobilization of the fungus A. japonicus, for the production of FOS and FFase.

Ethanol production using Saccharomyces cerevisiae cells immobilised on corn stem ground tissue

Cell immobilisation in alcoholic fermentation has been extensively studied during the past few decades because of its technical and economical advantages over those of free cell systems. A biocatalyst was prepared by immobilising a commercial Saccharomyces cerevisiae strain (baker yeast) on corn stem ground tissue for use in alcoholic fermentation. For this purpose, the yeast cells were submitted to the batch tests 'in situ' adsorption onto pieces of the corn stem ground tissue. Cells immobilisation was analysed by optical microscopy. It was determined that the addition of the corn stem ground tissue led to an increase of the pH value, total dissolved salts content, and sugar content in fermentation medium. The addition of 5 and 10g of the corn stem ground tissue per liter of medium, increased ethanol yield, decreased amount of residual sugar and the cells immobilisation was effective. Corn stem is one of the abundant, available, inexpensive, stable, reusable, nontoxic celulosic biomaterial with high porosity, which facilitates the transmission of substrates and products between carrier and medium. The prepared immobilised biocatalyst showed higher fermentation activity than free cells. The results indicate that corn stem might be an interesting support for yeast cell immobilisation, and also a cheap alternative recourse of mineral components with possibility of application for improving ethanol productivities.

Atrazine remediation in agricultural infiltrate by bioaugmented polyvinyl alcohol immobilized and free Agrobacterium radiobacter J14a

Bench-scale sand column breakthrough experiments were conducted to examine atrazine remediation in agricultural infiltrate by Agrobacterium radiobacter J14a (J14a) immobilized in phosphorylated-polyvinyl alcohol compared to free J14a cells. The effects of cell loading and infiltration rate on atrazine degradation and the loss of J14a were investigated. Four sets of experiments, i) tracers, ii) immobilized dead cells, iii) immobilized cells, and iv) free cells, were performed. The atrazine bioremediation at the cell loadings of 300, 600, and 900 mg dry cells l(-1) and the infiltration rates of 1, 3, and 6 cm d(-1) were tested for 5 column pore volumes (PV). The atrazine breakthrough results indicated that the immobilized dead cells significantly retarded atrazine transport. The atrazine removal efficiencies at the infiltration rates of 1, 3, and 6 cm d(-1) were 100%, 80-97%, and 50-70% respectively. Atrazine remediation capacity for the immobilized cells was not significantly different from the free cells. Both infiltration rate and cell loading significantly affected atrazine removal for both cell systems. The bacterial loss from the immobilized cell system was 10 to 100 times less than that from the free cell system. For long-term tests at 50 PV, the immobilized cell system provided consistent atrazine removal efficiency while the atrazine removal by the free cells declined gradually because of the cell loss.

Atrazine removal in agricultural infiltrate by bioaugmented polyvinyl alcohol immobilized and free Agrobacterium radiobacter J14a: A sand column study

Bench-scale sand column breakthrough experiments were conducted to examine atrazine removal in agricultural infiltrate by Agrobacterium radiobacter J14a (J14a) immobilized in phosphorylated-polyvinyl alcohol compared to free J14a cells. The effects of cell loading and infiltration rate on atrazine degradation and the loss of J14a were investigated. Four sets of experiments, (i) tracers, (ii) immobilized dead cells, (iii) immobilized cells, and (iv) free cells, were performed. The atrazine biodegradation at the cell loadings of 300, 600, and 900 mg dry cells L −1 and the infiltration rates of 1, 3, and 6 cm d −1 were tested for 5 column pore volumes (PV). The atrazine breakthrough results indicated that the immobilized dead cells significantly retarded atrazine transport. The atrazine removal efficiencies at the infiltration rates of 1, 3, and 6 cm d −1 were 100%, 80–97%, and 50–70%, respectively. Atrazine degradation capacity for the immobilized cells was not significantly different from the free cells. Both infiltration rate and cell loading significantly affected atrazine removal for both cell systems. The bacterial loss from the immobilized cell system was 10–100 times less than that from the free cell system. For long-term tests at 50 PV, the immobilized cell system provided consistent atrazine removal efficiency while the atrazine removal by the free cells declined gradually because of the cell loss.