Nitrate and phosphate removal by chitosan immobilized Scenedesmus

The effect of chitosan immobilization of Scenedesmus spp. cells on its viability, growth and nitrate and phosphate uptake was investigated. Scenedesmus sp. (strains 1 and 2) and Scenedesmus obliquus immobilized in chitosan beads showed high viability after the immobilization process. Immobilized Scenedesmus sp. strain 1 had a higher growth rate than its free living counterpart. Nitrate and phosphate uptake by immobilized cells of Scenedesmus sp. (strain 1), freely suspended cells and blank chitosan beads (without cells) were evaluated. Immobilized cells accomplished a 70% nitrate and 94% phosphate removal within 12h of incubation while free-living cells removed 20% nitrate and 30% phosphate within 36 h of treatment. Blank chitosan beads were responsible for up to 20% nitrate and 60% phosphate uptake at the end of the experiment. Chitosan is a suitable matrix for immobilization of microalgae, particularly Scenedesmus sp., but this system should be improved before its application for water quality control.     

Nitrate removal by immobilized cells of Phormidium uncinatum in batch culture and a continuous-flow photobioreactor

Cells of the non-N₂-fixing cyanobacterium Phormidium uncinatum were immobilized by adsorption into polyvinyl (PV-50) foam pieces. The effect of inoculum size as well as the initial inoculum/support ratio on the cell immobilization process was investigated. After 2 months of immobilization similar net O₂-exchange activity was measured in immobilized and free-living cells. Polyvinyl-adsorbed cells also showed similar nitrate uptake capacity to free-living cells. Nitrogen starvation promoted a remarkable increase in nitrate uptake rate of both free-living and immobilized cells. A lab-scale photobioreactor packed with polyvinyl foam pieces colonized in situ by cells was used for nitrate removal in a continuous mode. In the best working conditions found, nearly 90% of nitrate supplied in the influent (50 mg l^–1) was removed by cells having a residence time of 3–4 h. Correspondence to: J. L. Serra     

Nitrate and phosphate ion removal from water by Phormidium laminosum immobilized on hollow fibres in a photobioreactor

Removal of nitrate and phosphate ions from water, by using the thermophilic cyanobacterium Phormidium laminosum, immobilized on cellulose hollow fibres in the tubular photobioreactor at 43 °C, was studied by continuously supplying dilute growth medium for 7 days and then secondarily treated sewage (STS) for 12 days. The concentrations of NO⁻ ₃ and PO³⁻ ₄ in the effluent from the dilute growth medium decreased from 5.0 mg N/l to 3.1 mg N/l, and from 0.75 mg P/l to 0.05 mg P/l respectively, after a residence time of 12 h. The concentrations of NO⁻ ₃ and PO³⁻ ₄ in the effluent from STS decreased from 11.7 mg N/l to 2.0 mg N/l, and from 6.62 mg P/l to 0.02 mg P/l respectively, after a residence time of 48 h. The removal rates of nitrogenous␣and phosphate ions from STS were 0.24 and 0.11 mmol day⁻¹ l reactor⁻¹ respectively, under the same conditions. Although, among nitrogenous ions, nitrate and ammonium ions were efficiently removed by P.␣laminosum, the nitrite ion was released into the effluent when STS was used as influent. Treatment of water with thermophilic P. laminosum immobilized on hollow fibres thus appears to be an appropriate means for the removal of inorganic nitrogen and phosphorus from treated wastewater. Received: 15 August 1997 / Received last revision: 18 November 1997 / Accepted: 29 November 1997     

Nitrate removal in closed-system aquaculture by columnar denitrification.

The columnar denitrification method of nitrate-nitrogen removal from high-density, closed system, salmonid aquaculture was investigated and found to be feasible. However, adequate chemical monitoring was found to be necessary for the optimization and quality control of this method. When methanol-carbon was not balanced with inlet nitrate-nitrogen, the column effluent became unsatisfactory for closed-system fish culture due to the presence of excess amounts of nitrite, ammonia, sulfide, and dissolved organic carbon. Sulfide production was also influenced by column maturity and residence time. Methane-carbon was found to be unsatisfactory as an exogenous carbon source. Endogenous carbon could not support high removal efficiencies. Freshwater columns adpated readily to an artificial seawater with a salinity of 18% without observable inhibition. Scanning electron microscopy revealed that the bacterial flora was mainly rod forms with the Peritricha (protozoa) dominating as the primary consumers. Denitrifying bacteria isolated from freshwater columns were tentatively identified as species of Pseudomonas and Alcaligenes. A pilot plant column was found to behave in a manner similar to the laboratory columns except that nitrite production was never observed.     

Mercury removal by immobilized algae in batch culture systems

The accumulation and volatilization of mercury by non-immobilized and immobilizedChlorella emersonii have been studied in batch culture systems. Reduction in the mercury concentration in the growth medium by non-immobilized cells was highly dependent on inoculum density, whilst reduction in mercury concentration by immobilized cells was rapid at all inoculum densities. Mercury accumulation by immobilized cell biomass was significantly greater than by non-immobilized cells with 10⁶ and 10⁵ cells bead^–1 or ml^–1. Volatilization of mercury by non-immobilized cell systems was greatest at higher inoculum densities, whereas more mercury was volatilized from immobilized cell systems at lower inoculum densities, and was greatest with unstocked alginate beads. Thus, in immobilized systems, mercury removal from solution is complex and involves mercury accumulation by the cells and volatilization by the matrix and cells. Further studies of mercury accumulation and volatilization by unstocked immobilization matrices revealed that agarose volatilized much less mercury than alginate or agar. The precise mechanism of mercury volatilization by alginate remains unclear, though it is thought to be a chemical effect.     

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.     

Polyethylene glycol improves phenol removal by immobilized turnip peroxidase

Purified peroxidase from turnip (Brassica napus L. var. esculenta D.C.) was immobilized by entrapment in spheres of calcium alginate and by covalent binding to Affi-Gel 10. Both immobilized Turnip peroxidase (TP) preparations were assayed for the detoxification of a synthetic phenolic solution and a real wastewater effluent from a local paints factory. The effectiveness of phenolic compounds (PC's) removal by oxidative polymerization was evaluated using batch and recycling processes, and in the presence and in the absence of polyethylene glycol (PEG). The presence of PEG enhances the operative TP stability. In addition, reaction times were reduced from 3h to 10min, and more effective phenol removals were achieved when PEG was added. TP was able to perform 15 reaction cycles with a real industrial effluent showing PC's removals >90% PC's during the first 10 reaction cycles. High PC's removal efficiencies (>95%) were obtained using both immobilized preparations at PC's concentrations <1.2mM. Higher PC's concentrations decreased the removal efficiency to 90% with both preparations after the first reaction cycle, probably due to substrate inhibition. On the other hand, immobilized TP showed increased thermal stability when compared with free TP. A large-scale enzymatic process for industrial effluent treatment is expected to be developed with immobilized TP that could be stable enough to make the process economically feasible.     

Nitrate and nitrite uptake by free-living and immobilized N-started cells ofPhormidium laminosum

N-starved free-living and polyvinyl-immobilized cells ofPhormidium laminosum (strain OH-1-pCl₁) have been investigated in relation to their nitrate and nitrite uptake characteristics. N-deficient cells showed higher inorganic N-uptake rates than N-sufficient ones. The photosynthetic activities of the cells decreased progressively with the time of N-starvation. N-starved cells produced high amounts of exopolysaccharides, which appear to assist the immobilization process. Inorganic N-uptake by N-starved cells occurred in both light and dark under aerobic conditions. In anaerobiosis light was required for the uptake, confirming that the necessary energy might perhaps be derived from the respiratory electron transport chain under aerobiosis. Ammonium inhibited nitrate uptake but did not affect the uptake of nitrite. Initial nitrate and nitrite uptake rates were temperature-dependent and yielded hyperbolic curves when plotted against the N source concentration, indicating the existence of saturable transport system(s).     

Nitrate and nitrite removal from salted water by Haloferax mediterranei

Haloferax mediterranei is a denitrifying halophilic archaeon, able to assimilate nitrate or nitrite in the presence of oxygen by the assimilatory nitrate pathway. It can also grow in the presence of high nitrate or nitrite concentrations under anoxic conditions, using both nitrogen species as electron acceptors. In this study, the ability of H. mediterranei to remove high nitrate and nitrite concentrations from culture media has been demonstrated. This suggests that this haloarchaeon could be applied in water bioremediation processes to repair damage caused by anthropogenic activities. This could be beneficial in regions such as Comunidad Valenciana or Murcia (Spain), where the water tables contain high nitrate and nitrite concentrations due to fertiliser addition, and high salt concentrations due to marine intrusions.     

镉对固定化小球藻除磷效果的影响

采用人工配制污水进行静态模拟实验,研究了镉对被海藻酸钙凝胶包埋固定的小球藻去除磷能力的影响.结果表明:在各光照及pH条件下,镉对固定化小球藻吸收磷的效果随着实验时间的推移而变化,在实验的第一天时影响最大;总体而言,镉抑制了固定化小球藻的除磷能力,但在某些条件下镉反而提高了藻对磷的吸收;固定化处理减弱了镉对小球藻除磷能力的影响.具体的光照、pH值与镉的影响效果的关系尚待进一步探讨.     

Specific removal of endotoxin from protein solutions by immobilized histidine

A method for reducing endotoxin contamination in various solutions by immobilized histidine is described. Immobilized histidine is a porous adsorbent suitable for the adsorption of endotoxin with a high affinity over a wide range of pH and temperature and at low ionic strength (gamma/2 less than or equal to 0.1). When a purified endotoxin originating from Escherichia coli UKT-B was studied, the apparent dissociation constant between endotoxin and the adsorbent was 7.3 X 10(-13) M. The adsorbent was able to remove various kinds of endotoxin originating from gram-negative bacteria; the concentration of endotoxin was reduced from 1000 to less than 0.01 ng/ml in water. It is shown that the adsorbent specifically adsorbs endotoxin provided that the adsorption conditions are properly selected. Some examples of the specific removal of endotoxin from high-molecular-weight physiologically active substances such as tumor necrosis factor and lysozyme are shown.     

Enhanced lindane removal from soil slurry by immobilized Streptomyces consortium

The aim of this work was to assess lindane removal from soil slurry by a Streptomyces consortium immobilized in cloth sachets, at different inoculum, lindane and slurry concentrations. In concentrated slurry (soil/water ratio of 2:3), the higher lindane removal (35.3 mg Kg⁻¹) was obtained with the medium inoculum (10⁷ CFU g⁻¹) and the highest lindane concentration tested, at 7 days of incubation. Although, lindane removal was also detected in abiotic controls, probably caused by pesticide adsorption to soil particles. Thus, these parameters were selected for evaluating the pesticide removal in diluted slurry (soil/water ratio of 1:4). After 14 days of incubation, 28.7 mg Kg⁻¹ of lindane were removed. Also, a phytotoxicity assay demonstrated that seeds growing on diluted slurries bioremediated during 7 and 14 days, showed an improvement in biological parameters, compared to those growing on non-bioremediated slurries. Thus, bioremediated slurries would not have toxic effects on lettuce seeds.     

Diesel oil removal by immobilized Pseudoxanthomonas sp. RN402

Pseudoxanthomonas sp. RN402 was capable of degrading diesel, crude oil, n-tetradecane and n-hexadecane. The RN402 cells were immobilized on the surface of high-density polyethylene plastic pellets at a maximum cell density of 10⁸ most probable number (MPN) g^?1 of plastic pellets. The immobilized cells not only showed a higher efficacy of diesel oil removal than free cells but could also degrade higher concentrations of diesel oil. The rate of diesel oil removal by immobilized RN402 cells in liquid culture was 1,050 mg l^?1 day^?1. Moreover, the immobilized cells could maintain high efficacy and viability throughout 70 cycles of bioremedial treatment of diesel-contaminated water. The stability of diesel oil degradation in the immobilized cells resulted from the ability of living RN402 cells to attach to material surfaces by biofilm formation, as was shown by CLSM imaging. These characteristics of the immobilized RN402 cells, including high degradative efficacy, stability and flotation, make them suitable for the purpose of continuous wastewater bioremediation.     

Hydrogen sulfide removal by immobilized autotrophic and heterotrophic bacteria in the bioreactors

Summary Autotrophic Thiobacillus sp. CH11 and heterotrophic Pseudomonas putida CH11 were isolated from piggery waste water. Extensive tests, including removal action, removal efficiency, removal capacity, and adaptability to perturbed conditions were conducted on autotrophic and heterotrophic biofilters. The results clearly demonstrate the application potential of autotrophic and heterotrophic biofilters for the continuous H₂S removal under different perturbed conditions.     

Ammonia removal from livestock wastewater by ammonia-assimilating microorganisms immobilized in polyvinyl alcohol

We isolated ammonia-assimilating microorganisms from the livestock manure treatment systems and evaluated their ammonia-assimilating ability. Many isolates utilized ammonia at high rates when they were purely cultivated in a nitrogen-limited medium to which sterilized lagoon extract had been added. Some isolates that were immobilized in polyvinyl alcohol (PVA) utilized ammonia present in the media containing viable lagoon microorganisms. Staining with 4′,6′-diamidino-2-phenylindole (DAPI) indicated that the immobilized high ammonia-assimilating isolates grew dominantly within the PVA beads. High ammonia-assimilating isolates in the mixed culture containing viable lagoon microorganisms were identified as Pseudomonas spp. and member of Rhizobiaceae species by partial sequencing of the 16S ribosomal DNA.     

Wastewater nutrient removal with microalgae immobilized in carrageenan

Two species of the green freshwater microalga Scenedesmus have been immobilized in beads of κ-carrageenan. Growth curves were similar to those observed with free cells. The uptake of nitrogen and phosphorus from wastewater was similar for free and entrapped microalgae. The reduction of N-NH⁺₄ was 90% within 4 h at pH 9.0 and 70% within 5 h at an adjusted pH of 7.7. From these experiments, we conclude that immobilized Scenedesmus microalgae can grow well within gel beads and that they are as physiologically active for wastewater nutrient removal as free cells.     

Error removal in microchip-synthesized DNA using immobilized MutS

The development of economical de novo gene synthesis methods using microchip-synthesized oligonucleotides has been limited by their high error rates. In this study, a low-cost, effective and improved-throughput (up to 32 oligos per run) error-removal method using an immobilized cellulose column containing the mismatch binding protein MutS was produced to generate high-quality DNA from oligos, particularly microchip-synthesized oligonucleotides. Error-containing DNA in the initial material was specifically retained on the MutS-immobilized cellulose column (MICC), and error-depleted DNA in the eluate was collected for downstream gene assembly. Significantly, this method improved a population of synthetic enhanced green fluorescent protein (720 bp) clones from 0.93% to 83.22%, corresponding to a decrease in the error frequency of synthetic gene from 11.44/kb to 0.46/kb. In addition, a parallel multiplex MICC error-removal strategy was also evaluated in assembling 11 genes encoding ∼21 kb of DNA from 893 oligos. The error frequency was reduced by 21.59-fold (from 14.25/kb to 0.66/kb), resulting in a 24.48-fold increase in the percentage of error-free assembled fragments (from 3.23% to 79.07%). Furthermore, the standard MICC error-removal process could be completed within 1.5 h at a cost as low as $0.374 per MICC.     

Efficient removal of toxic phthalate by immobilized serine-type aldehyde-tagged esterase G

Esterase G (EstG) from dibutyl phthalate (DBP)-degrading Sphingobium sp. SM42 was immobilized on amine-functionalized supports through aldehyde tag technology. Two different sulfatase motif tags, either LCTPSR (cysteine-type) or MSAPAR (serine-type), each of which is recognized by a specific formylglycine generating enzyme (FGE), were fused to the C-terminus of EstG. The cysteine-specific FGE was derived from Pseudomonas putida KT2440 while Klebsiella sp. SLS5 provided serine-specific FGE. The EstG with serine-type aldehyde tag showed a greater immobilization yield and higher specific activity by 4.8-fold and 1.8-fold, respectively. The immobilized EstG retained over 90% of its original activity after seven cycles of usage, and exhibited significantly improved thermostability by retaining 66% activity after 1 h incubation at 60 °C. Additionally, nearly 100% and over 30% of the DBP in 10 mM and 100 mM solutions, respectively, was degraded by the immobilized EstG within 18 h.     

Atmospheric methane removal by methane-oxidizing bacteria immobilized on porous building materials

Biological treatment using methane-oxidizing bacteria (MOB) immobilized on six porous carrier materials have been used to mitigate methane emission. Experiments were performed with different MOB inoculated in building materials at high (~20 % (v/v)) and low (~100 ppmv) methane mixing ratios. Methylocystis parvus in autoclaved aerated concrete (AAC) exhibited the highest methane removal rate at high (28.5?±?3.8 μg CH₄ g^?1 building material h^?1) and low (1.7?±?0.4 μg CH₄ g^?1 building material h^?1) methane mixing ratio. Due to the higher volume of pores with diameter >5 μm compared to other materials tested, AAC was able to adsorb more bacteria which might explain for the higher methane removal observed. The total methane and carbon dioxide-carbon in the headspace was decreased for 65.2?±?10.9 % when M. parvus in Ytong was incubated for 100 h. This study showed that immobilized MOB on building materials could be used to remove methane from the air and also act as carbon sink.     

Heavy metal removal by novel CBD-EC20 sorbents immobilized on cellulose

Heavy metals are major contributors to pollution of the biosphere, and their efficient removal from contaminated water is required. Biosorption is an emerging technology that has been shown to be effective in removing very low levels of heavy metal from wastewater. Although peptides such as metallothioneins or phytotchelatins are known to immobilize heavy metals, peptide-based biosorbents have not been extensively investigated. In this paper, we describe the construction and expression of bifunctional fusion proteins consisting of synthetic phytochelatin (EC20) linked to a Clostridium-derived cellulose-binding domain (CBD(clos)), enabling purification and immobilization of the fusions onto different cellulose materials in essentially a single step. The immobilized sorbents were shown to be highly effective in removing cadmium at parts per million levels. Repeated removal of cadmium was demonstrated in an immobilized column. The ability to genetically engineer biosorbents with precisely defined properties could provide an attractive strategy for developing high-affinity bioadsorbents suitable for heavy metal removal.