Removal of 1,1′-Dimethyl-4,4′bipyridyl Dichloride from Aqueous Solution by Natural and Activated Bentonite

The sorption of 1,1′-dimethyl-4,4′bipyridilium dichloride (paraquat) on bentonite desiccated at 110°C untreated, and acid-treated with H₂SO₄ solutions over a concentration range between 0·25 M and 1·00 M , from aqueous solution at 30°C has been studied by using batch experiments. In addition, column experiments were carried out with the bentonite sample treated with the 1·00 M H₂SO₄ solution [B-A(1·00)] by using two aqueous solutions of paraquat of different concentrations (C = 29·40 mg dm⁻³ and C = 65·38 mg dm⁻³). The experimental data points have been fitted to the Langmuir equation in order to calculate the sorption capacities (X_m) of the samples; X_m values range from 1·35×10⁵ mg kg⁻¹ for the sample acid-treated with 0·375 M H₂SO₄ [B-A(0·375)] up to 1·96×10⁵ mg kg⁻¹ for the untreated bentonite [B-N]. The removal efficiency (R) has also been calculated; R values ranging from 44·61% for the [B-A(0·375)] sample up to 67·23% for B-N. The batch experiments show that the natural bentonite is more effective than the acid-treated bentonite in relation to sorption of paraquat. The column experiments show that the B-A(1·00) sample might be reasonably used in removing paraquat, the column efficiency increasing from 37·55% for the C = 65·38 mg dm⁻³ aqueous solution of paraquat up to 66·58% for the C = 29·40 mg dm⁻³ one. © 1997 SCI.     

Adsorption of chlorophyll-a from acetone solution on natural and activated bentonite

The adsorption of chlorophyll-a on bentonite desiccated at 110°C, untreated and acid-treated with H₂SO₄ solutions over a concentration range between 0·25 and 2·50 mol dm^?3, from acetone solution at 25°C has been studied. The adsorption isotherms may be classified as using Giles' classification, as type S (untreated sample and 0·25 mol dm^?3 H₂SO₄-treated sample), type H (0·50 mol dm^?3 H₂SO₄-treated sample) and type L (1·00 and 2·50 mol dm^?3 H₂SO₄-treated samples). This fact suggests that the bentonite surfaces (low, high and medium affinity, respectively) behave in differently relation to the adsorption of the chlorophyll-a molecules. The experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K_f) of the samples; K_f values range from 0·43 mg kg^?1 for the untreated bentonite up to 108·89 mg kg^?1 for the 0·50 M H₂SO₄-treated bentonite. The removal efficiencies (R) have also been calculated and range from 5·71% for the untreated bentonite up to 85·18% for the 0·50 M H₂SO₄-treated bentonite.     

Removal of chloridazon from water by kerolite/stevensite and bentonite: a comparative study

The adsorption of chloridazon (5‐amino‐4‐chloro‐2‐phenylpyridazin‐3(2H)‐one) on a new type of material formed by kerolite/stevensite bearing lithofacies and on a bentonite, desiccated at 110 °C from aqueous solution at 25 °C has been studied by using batch experiments. In addition, column experiments were carried out with these samples using aqueous solutions of chloridazon at a concentration (C) of 45 × 10⁻⁴ cmol dm⁻³. The experimental data points have been fitted to the Langmuir equation to calculate the adsorption capacities (X_m). Values for X_m ranged from 0.072 cmol kg⁻¹ for bentonite up to 1.30 cmol kg⁻¹ for kerolite. The removal efficiency, R, ranged from 17.1% for bentonite up to 85.1% for kerolite. The batch experiments show that the kerolite is more effective than bentonite in adsorbing chloridazon. The column experiments show that kerolite might be reasonably used in removing chloridazon, the data indicating that a readily available and inexpensive Spanish kerolite can be employed as a filter for contaminated waters with chloridazon, so controlling its release to the environment. © 2000 Society of Chemical Industry     

Adsorption of cadmium and zinc from aqueous solution on natural and activated bentonite

The adsorption of cadmium and zinc ions on natural bentonite heat-treated at 110°C or at 200°C and on bentonite acid-treated with H₂SO₄ (concentrations: 0·5 mol dm^?3 and 2·5 mol dm^?3), from aqueous solution at 30°C has been studied. The adsorption isotherms corresponding to cadmium and zinc may be classified respectively as H and L types of the Giles classification which suggests the samples have respectively a high and a medium affinity for cadmium and zinc ions. The experimental data points have been fitted to the Langmuir equation in order to calcualte the adsorption capacities (X_m) and the apparent equilibrium constants (K_a) of the samples; X_m and K_a values range respectively for 4·11 mg g^?1 and 1·90 dm³ g^?1 for the sample acid-treated with 2·5 mol dm^?3 H₂SO₄ [(B)-A(2·5)] up to 16·50 mg g^?1 and 30·67 dm³ g^?1 for the natural sample heat-treated at 200°C [B-N-200], for the adsorption process of cadmium, and from 2·39 mg g^?1 and 0·07 dm³ g^?1, also for B-A(2·5), up to 4·54 mg g^?1 and 0·45 dm³ g^?1 [B-N-200], for the adsorption process of zinc. X_m and K_a values for the heat-treated natural samples were higher than those corresponding to the acid-treated ones. The removal efficiency (R) has also been calculated for every sample; R values ranging respectively from 65·9% and 8·2% [B-A(2·5)] up to 100% and 19·9% [B-N-200], for adsorption of cadmium and zinc.     

Removal of 3—(3,4—dichlorophenyl)—1, 1 dimethylurea from aqueous solution by natural and activated bentonite

The adsorption of 3-(3,4-dichlorophenyl)-1,1 dimethylurea (diuron) on bentonite desiccated at 110°C untreated, and acid treated with H₂SO₄ solutions over a concentration range between 0.25 M and 5.00 M, from aqueous solution at 30°C has been studied. In addition, adsorption of diuron on combined acid/heat treated samples (0.50 M and 2.50 M H₂SO₄/200°C and 400°C) has also been studied. The experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K) of the samples; K values range from 0.92 μg g^?1 for the untreated bentonite up to 974.42 μg g^?1 for the 0.50 M H₂SO₄/400°C acid/heat treated bentonite. The removal efficiency (R) has also been calculated; R values ranging from 2.02% for the untreated bentonite up to 97.17% for the 0.50 M H₂SO₄/400°C acid/heat treated bentonite. The adsorption experiments show that bentonite heat treatment is more effective than bentonite acid treatment in relation to adsorption of diuron.     

Evaluation of biosorbents for Cu removal from wastewater in the presence of EDTA

BACKGROUND: This paper evaluates the use of several biosorbents for Cu removal from aqueous solutions in the absence and presence of ethylenediaminetetraacetic acid (EDTA). The objective was to determine the applicability of the sorption process after conventional physicochemical wastewater treatment, or as primary treatment, replacing the physicochemical process. RESULTS: Fixed‐bed experiments were performed at Cu influent concentrations of 2 and 20 mg dm^?3 and EDTA doses between 0 and 10 mg dm^?3. At low Cu concentration without EDTA, Cu uptake capacity followed the order Posidonia oceanica > chitosan > chitin > Scharlau AC > Darco AC, with a maximum, at C/C₀ = 0.2, of 23.2 mg g^?1. In the presence of EDTA, Cu was detected in the effluent from the beginning of the operation, except for the activated carbons and chitosan at low EDTA doses. At higher EDTA doses, the activated carbons showed the best performance. Uptakes at Cu concentration of 20 mg dm^?3 without EDTA were 51.6 (Posidonia oceanica) and 41.4 mg g^?1 (chitosan) at C/C₀ = 0.2. CONCLUSION: A sequence of one fixed bed with Posidonia oceanica followed by another with Scharlau AC should be an alternative to Cu precipitation, with Cu effluent concentration lower than 0.5 mg dm^?3 for more than 350 pore volumes. Copyright © 2007 Society of Chemical Industry     

Anaerobic and aerobic treatment of a simulated textile effluent

A simulated textile effluent (STE) was generated for use in laboratory biotreatment studies; this effluent contained one reactive azo dye, PROCION Red H‐E7B (1.5 g dm⁻³); sizing agent, Tissalys 150 (1.9 g dm⁻³); sodium chloride (1.5 g dm⁻³) and acetic acid (0.53 g dm⁻³) together with nutrients and trace elements, giving a mean COD of 3480 mg dm⁻³. An inclined tubular anaerobic digester (ITD) was operated for 9 months on the STE and a UASB reactor for 3 months. For a 57 day period anaerobic effluent from two reactors, a UASB and an ITD, was mixed and treated in an aerobic stage. In days 77–247 68% of the true colour of PROCION Red H‐E7B was removed by anaerobic treatment with no colour removal aerobically and up to 37% COD was removed anaerobically, with a corresponding BOD removal of 71%. For combined anaerobic and aerobic treatment a mean COD removal of 57% and BOD removal of 86% was achieved. Operation of the ITD at a 2.8 day HRT (volumetric loading rate (B _v) 1.24 g COD dm⁻³day⁻¹) and the UASB at a 2 day HRT (B _v 1.74 g COD dm⁻³day⁻¹) gave comparable COD removals but the UASB gave better true colour removal. Effluent from the combined process operating on this simulated waste still contained an average 1500 mg COD dm⁻³, and further treatment would be required to meet consent standards. © 1999 Society of Chemical Industry     

Triazidotrinitro Benzene: 1,3,5‐(N3)3‐2,4,6‐(NO2)3C6

Triazidotrinitro benzene, 1,3,5‐(N₃)₃‐2,4,6‐(NO₂)₃C₆ ( 1 ) was synthesized by nitration of triazidodinitro benzene, 1,3,5‐(N₃)₃‐2,4‐(NO₂)₂C₆H with either a mixture of fuming nitric and concentrated sulfuric acid (HNO₃/H₂SO₄) or with N₂O₅. Crystals were obtained by the slow evaporation of an acetone/acetic acid mixture at room temperature over a period of 2 weeks and characterized by single crystal X‐ray diffraction: monoclinic, P 2₁/c (no. 14), a=0.54256(4), b=1.8552(1), c=1.2129(1) nm, β=94.91(1)°, V=1.2163(2) nm³, Z=4, ϱ=1.836 g⋅cm⁻³, R_all =0.069. Triazidotrinitro benzene has a remarkably high density (1.84 g⋅cm⁻³). The standard heat of formation of compound 1 was computed at B3LYP/6‐31G(d, p) level of theory to be ΔH°_f=765.8 kJ⋅mol⁻¹ which translates to 2278.0 kJ⋅kg⁻¹. The expected detonation properties of compound 1 were calculated using the semi‐empirical equations suggested by Kamlet and Jacobs: detonation pressure, P=18.4 GPa and detonation velocity, D=8100 m⋅s⁻¹.     

Removal of trivalent chromium(III) from solution by biosorption in cork powder

The removal of trivalent chromium from solutions using biosorption in cork powder is described. The adsorption isotherm was determined, along with the effect of different variables, such as biomass particle size, solid–liquid ratio, reaction time, metal concentration and pH, on the efficiency of chromium removal. It was concluded that the adsorption is slow and favoured by an increase in pH. Therefore, using a solid–liquid ratio of 4 g dm^?3 it is possible to reduce the chromium concentration in the solution from 10 mg dm^?3 to less than 1.5 mg dm^?3 in 2 h at 22 °C. The kinetic studies verified that the sorption of chromium by cork was described by a second‐order model. The elution results showed that 50% of the chromium bound to the cork was eluted using 0.5 mol dm^?3 H₂SO₄ and that cork maintains its binding capacity over four cycles of biosorption/elution. © 2002 Society of Chemical Industry     

Behaviors of polyelectrolyte AAm/AMPS/bentonite composite hydrogels in uptake of uranyl ions from aqueous solutions

Uranyl ion (UO₂²⁺) sorption properties of polyelectrolyte composite hydrogels made by the polymerization of acrylamide (AAm) with 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) and clay such as bentonite (Bent) were investigated as a function of composition to find materials with swelling and uranyl ion sorption properties. Highly swollen AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with AMPS as co‐monomer and two multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4 butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. The influence of AMPS content in hydrogels was examined. Uranyl ion adsorption from aqueous solutions was studied by batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of AMPS on the uranyl ion adsorption were examined. Finally, adsorption capacity (the amount of sorbed uranyl ion per gram of dry hydrogel) (q) was calculated to be 0.67 × 10⁻³–2.11 × 10⁻³ mol uranyl ion per gram for the hydrogels. Removal effiency of uranyl ions (RE%) was changed range 9.05–29.92%. The values of partition ratio (K_d) of uranyl ions was calculated to be 0.10–0.43 for AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels, respectively. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Preliminary studies in removing atrazine,isoproturon and imidacloprid from water by natural sepiolite

Sepiolite is a hydrated magnesium silicate clay with a fibrous structure and binder properties. To calculate the potential use of sepiolite in removing atrazine [2‐chloro‐4‐ethylamino‐6‐isopropilamino‐1,3,5,‐triazine], isoproturon [3‐(4‐isopropylphenyl)‐1,1‐dimethylurea] and imidacloprid [1‐(6‐chloro‐3‐pyridinylmethyl)‐N‐nitroimidazolin‐2‐ylideneamine] from water, the adsorption of atrazine, isoproturon and imidacloprid on sepiolite desiccated at 110 °C from aqueous solution at 25 °C has been studied by using batch experiments. In addition, column experiments were carried out with the sepiolite sample using aqueous solutions of atrazine, isoproturon and imidacloprid at a concentration of 20.0 × 10⁻⁴ cmol dm⁻³. The experimental data points have been fitted to the Langmuir equation to calculate the adsorption capacities (X_m). Values for X_m ranged from 2.70 × 10⁻¹ cmol kg⁻¹ for isoproturon up to 3.97 × 10⁻¹ cmol kg⁻¹ for atrazine. The removal efficiency (R) ranged from 36.7% for isoproturon up to 74.3% for atrazine. The batch experiments show that the sepiolite is more effective in adsorbing atrazine than imidacloprid and isoproturon. The column experiments show that sepiolite might be reasonably used in removing atrazine, the column efficiency being 46%. The data indicate that a readily available and inexpensive Spanish sepiolite can be employed as a filter for contaminated waters with these pesticides, controlling their release to the environment. © 1999 Society of Chemical Industry     

Influence of the physical-chemistry properties of an acid-activated bentonite in the bleaching of olive oil

The bleaching process at 90°C of an olive oil from Jaen (Spain) using natural bentonite and bentonite acid treated with H₂SO₄ (over a concentration range between 0.50 M and 5.00 M) has been studied. The bleaching capacities of the bentonite samples were calculated by applying the Freundlich equation to the experimental data points corresponding to the bleaching process. The bleaching capacities (K_F parameter) range from 2.5 × 10^?7 for non-treated bentonite up to 0.85 for 2.50 M H₂SO₄ treated bentonite. The bleaching capacity of the 5.00 M H₂SO₄ treated bentonite (K_F = 0.81) is less than that of the 2.50 M H₂SO₄ treated bentonite.     

Synthesis,Surface and Interfacial Properties of Dodecyl Diphenyl Oxide Disulfonate with Different Counterions

Dodecyl diphenyl oxide disulfonate with different counterions (C₁₂MADS‐M, M = Na, Mg, Ca) were synthesized using dodecyl alcohol, diphenyl oxide and SO₃ as reagents through alkylation–sulfonation–neutralization. The structure of the product was characterized by infrared spectroscopy and electrospray ionization‐mass spectrometry. The surface and interfacial prosperities were investigated. The critical micelle concentration (CMC) of C₁₂MADS‐Na, C₁₂MADS‐Mg and C₁₂MADS‐Ca was 1.23 × 10^?3, 5.25 × 10^?4 and 5.37 × 10^?4 mol/L, respectively. The surface tension at CMC (γ_CMC) of C₁₂MADS‐Na, C₁₂MADS‐Mg and C₁₂MADS‐Ca was 43.2, 37.1 and 36.6 mN/m, respectively. Interfacial tensions between crude oil and C₁₂MADS‐M aqueous solution gave only a small change in the calcium chloride concentrations ranging from 50 to 10,000 mg/L.     

Colour removal from textile effluents using hardwood sawdust as an absorbent

Decolourisation of a dilute solution of a basic dyestuff was carried out by using hardwood sawdust as adsorbent. At 80°C 85% decolourisation occurred within 100 min at an initial concentration (C_o) of 200 mg dm^?3. There was a 44% reduction in contact time when the temperature was raised from 25 to 80°C. The rate parameter for different initial dye concentrations was found to follow the equation: k_co=4.20C_o^0.88 and the rate parameter for different mean diameter d_m followed the equation k_dm=4.1 (l/d_m)^0.135. The activation energy of the process was 9.83 kJ mol^?1 which shows that the rate controlling step is intraparticle diffusion.     

The role of sulfate as a competitive inhibitor of enzymatically‐mediated heavy metal uptake by Citrobacter sp: implications in the bioremediation of acid mine drainage water using biogenic phosphate precipitant

Heavy metals can be removed from solution via biocrystallization with enzymatically‐liberated inorganic phosphate, according to Michaelis–Menten kinetics, in free whole cells and cells immobilized within polyacrylamide gel in a flow‐through reactor. Sulfate is a competitive inhibitor of phosphate release and a predictive model was developed and shown to describe the effect of sulfate on the efficiency of phosphate release by flow‐through columns. The inhibitory effect was substantially less than anticipated in the case of metal removal by the columns. In the case of lanthanum removal metal removal efficiency was restored by increasing the substrate concentration in accordance with model predictions. In the case of uranyl ion its removal with an equivalent substrate supplement increased the activity by 20% over the initial value at a limiting flow rate. Since the initial loss in activity in the presence of 40 mmol dm⁻³ SO₄²⁻ (approximately twice the K_i value) was only approximately 20% with both metals this was considered to be a minor problem for bioprocess application. In confirmation, calculations made from a published ‘case history’ of application of the system to the bioremediation of acid mine drainage water (AMD) containing 0.22 mmol dm⁻³ of uranyl ion and 35 mmol dm⁻³ of SO showed that the benchscale model is a good representation of performance under actual load conditions. © 1999 Society of Chemical Industry     

Regeneration of activated carbon after contact with sulfuric acid solution

This study deal's with the feasible use of a commercial activated carbon in the uptake of H₂SO₄ from aqueous solution and with the regeneration of the spent product. Thermogravimetry TG and FT‐IR spectroscopy are used in the analysis of samples. The activated carbon is a very effective material for the uptake of H₂SO₄. Using a 9.0 mol dm⁻³ H₂SO₄ solution, the mass increase is 37.8 wt%. From the sample obtained, the H₂SO₄ can be removed largely either by heating at 250 °C for 2 h in a N₂ atmosphere or by washing thoroughly with distilled water for 24 h. The mass loss in both cases amounts to 33.6 wt%. The FT‐IR spectroscopy results indicate that the surface chemistry of the carbon is not affected, noticeably, at least, after its contact with the H₂SO₄ solution. The behavior of H₂SO₄ toward carbon is compared with that of HNO₃. © 2000 Society of Chemical Industry     

Biosorptive uranium uptake by a Pseudomonas strain: characterization and equilibrium studies

The biosorptive uranium(VI) uptake capacity of live and lyophilized Pseudomonas cells was characterized in terms of equilibrium metal loading, effect of solution pH and possible interference by selected co‐ions. Uranium binding by the test biomass was rapid, achieving >90% sorption efficiency within 10 min of contact and the equilibrium was attained after 1 h. pH‐dependent uranium sorption was observed for both biomass types with the maximum being at pH 5.0. Metal uptake by live cells was not affected by culture age and the presence of an energy source or metabolic inhibitor. Sorption isotherm studies at a solution pH of either 3.5 or 5.0 indicated efficient and exceptionally high uranium loading by the test biomass, particularly at the higher pH level. At equilibrium, the lyophilized Pseudomonas exhibited a metal loading of 541 ± 34.21 mg g^?1 compared with a lower value by the live organisms (410 ± 25.93 mg g^?1). Experimental sorption data showing conformity to both Freundlich and Langmuir isotherm models indicate monolayered uranium binding by the test biomass. In bimetallic combinations a significant interference in uranium loading was offered by cations such as thorium(IV), iron(II and III), aluminium(III) and copper(II), while the anions tested, except carbonate, were ineffective. Uranium sorption studies in the presence of a range of Fe³⁺ and SO₄^2? concentrations indicate a strong inhibition (80%) by the former at an equimolar ratio while more than 70% adsorption efficiency was retained even at a high sulfate level (30 000 mg dm^?3). Overall data indicate the suitability of the Pseudomonas sp biomass in developing a biosorbent for uranium removal from aqueous waste streams. © 2001 Society of Chemical Industry     

Characteristics of gold biosorption from cyanide solution

Gold adsorption from cyanide solution by bacterial (Bacillus subtilis), fungal (Penicillium chrysogenum) and seaweed (Sargassum fluitans) biomass was examined. At pH 2.0, these biomass types were capable of sequestering up to 8.0 µmol g⁻¹, 7.2 µmol g⁻¹ and 3.2 µmol g⁻¹, respectively. An adverse effect of increasing solution ionic strength (NaNO₃) on gold biosorption was observed. Gold‐loaded biomass could be eluted with 0.1 mol dm⁻³ NaOH with efficiencies higher than 90% at pH 5.0 at the Solid‐to‐Liquid ratio, S/L, = 4 (g dm⁻³). Cyanide mass balances for the adsorption, desorption as well as for the AVR process indicated the stability of the gold‐cyanide which did not dissociate either upon acidification or upon binding by biomass functional groups. Gold biosorption mainly involved anionic AuCN₂⁻ species bound by ionizable biomass functional groups carrying a positive charge when protonated. FTIR analyses indicated that the main biomass functional groups involved in gold biosorption are most probably nitrogen‐containing weak base groups. The present results confirmed that waste microbial biomaterials have some potential for removing and concentrating gold from solutions where it occurs as a gold‐cyanide complex. © 1999 Society of Chemical Industry     

Redox polymer with N,N‐dichlorosulfonamide functional groups as arsenite oxidant in aqueous solutions

A macroporous, styrene‐divinylbenzene polymer with N,N‐dichlorosulfonamide functional groups (? SO₂NCl₂), containing two chlorine atoms with oxidation number +1, have been prepared through the chemical modification of a commercial sulfonic cation exchanger (Amberlyst 15, Rohm and Haas). Obtained product was used as the heterogeneous oxidant of As(III) in aqueous solutions. The polymer's oxidizing capacity, determined as part of the batch studies, amounted to 193.29 mg As(III) g^?1 (pH = 7.7) and 206.03 mg As(III) g^?1 (pH = 2.0). The suitability of the redox polymer for long‐lasting operation in the aqueous environment was confirmed in the column study conducted using a solution with a concentration of 10 mg As(III) dm^?3 at a flow rate of 6 bed volumes (BV) h^?1. The concentration of As(III) in the effluent reached the value of 0.01 mg As(III) dm^?3 only after 8 weeks of continuous operation when 7930 BV of the solution had passed through the bed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41552.     

Production of GST–SOD fusion protein by recombinant E coli XL1 Blue

A recombinant plasmid was constructed by inserting a DNA fragment with the coding region of Cu/Zn–superoxide dismutase (Cu/Zn–SOD) cDNA from sweet potato, Ipomoea batatas (l) Lam cv Tainong 57, into the 3′ end of the open reading frame of the glutathione S‐transferase (GST) gene in an expression vector, pGEX‐2T. The constructed plasmid was transformed into E coli XL1 Blue. Fusion proteins of Cu/Zn–SOD and GST (GST–SOD) were produced from the recombinant E coli. About 6 mg of GST–SOD fusion proteins could be obtained from 1 dm³ of cultural broth after induction with 0.075 mmol dm⁻³ Isopropyl‐β‐D ‐thiogalactoside (IPTG). Lactose was not an efficient inducer. High cell density culture was performed by fed‐batch fermentation using a glucose analyzer to control glucose concentration at 1 g dm⁻³. The cell density of the fed‐batch culture reached an OD₆₀₀ of 30, the total amount of GST–SOD fusion protein was 100 mg dm⁻³ which is about 14 times more than that of the batch culture. Most of the fusion proteins were shown to be in an active monomeric form, and the molecular weight was estimated to be 45 kDa by SDS–PAGE and 47 kDa by gel filtration. The specific activity of the purified fusion proteins was about 1200 mg⁻¹ and equal to 3200 unit per mg of SOD domain only. © 2000 Society of Chemical Industry