Study on the characterization of lead (II) biosorption by fungus <Emphasis Type="Italic">Aspergillus parasiticus</Emphasis>

The lead (II) biosorption potential of Aspergillus parasiticus fungal biomass has been investigated in a batch system. The initial pH, biosorbent dosage, contact time, initial metal ion concentrations and temperature were studied to optimize the biosorption conditions. The maximum lead (II) biosorption capacity of the fungal biosorbent was found as 4.02 × 10⁻⁴ mol g⁻¹ at pH 5.0 and 20°C. The biosorption equilibrium was reached in 70 min. Equilibrium biosorption data were followed by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. In regeneration experiments, no significant loss of sorption performance was observed during four biosorption-desorption cycles. The interactions between lead (II) ions and biosorbent were also examined by FTIR and EDAX analysis. The results revealed that biosorption process could be described by ion exchange as dominant mechanism as well as complexation for this biosorbent. The ion exchange mechanism was confirmed by E value obtained from D-R isotherm model as well.     

Biosorption of radioactive thorium by Sargassum filipendula

In the present work, the biosorption of radioactive thorium was investigated using a dry biomass of Sargassum filipendula as the biosorbent material. Radioactive solutions containing between 2.0 and 500.0μg thorium were tested by biosorption with S. filipendula, yielding uptake capacities from 20 to 100%, depending on the concentration of the solution. Kinetic studies indicated that equilibrium between the thorium solution and the solid fraction was achieved after three hours of contact and that a second-order model could express the equilibrium kinetics. In order to investigate the maximum biosorption capacity of the biomass an isotherm was done, based on the experimental data, which revealed the maximum uptake capacity to be 2.59 μmol thorium/g biomass. The experimental data fitted well to a Langmuir model, which provided a good correlation between the experimental and predicted thorium uptake values.     

Biosorption of lead(II) from aqueous solutions by non-living algal biomass Oedogonium sp. and Nostoc sp.--a comparative study

Industrial wastewaters containing heavy metals pose a major environmental problem that needs to be remedied. The present study reports the ability of two non-living (dried) fresh water algae, Oedogonium sp. and Nostoc sp. to remove lead(II) from aqueous solutions in batch system under varying range of pH (2.99-7.04), contact time (5-300 min), biosorbent dose (0.1-0.8 g/L), and initial metal ion concentrations (100 and 200mg/L). The optimum conditions for lead biosorption are almost same for the two algal biomass Oedogonium sp. and Nostoc sp. (pH 5.0, contact time 90 and 70 min, biosorbent dose 0.5 g/L and initial Pb(II) concentration 200mg/L) however, the biomass of Oedogonium sp. was found to be more suitable than Nostoc sp. for the development of an efficient biosorbent for the removal of lead(II) from aqueous solutions, as it showed higher values of q(e) adsorption capacity (145.0mg/g for Oedogonium sp. and 93.5mg/g for Nostoc sp.). The equilibrium data fitted well in the Langmuir isotherms than the Freundlich isotherm, thus proving monolayer adsorption of lead on both the algal biomass. Analysis of data shows that the process involves second-order kinetics and thermodynamic treatment of equilibrium data shows endothermic nature of the adsorption process. The spectrum of FTIR confirms that the amino and carboxyl groups on the surface of algal biomass were the main adsorption sites for lead removal. Both the biosorbents could be regenerated using 0.1 mol/L HCl solution, with upto 90% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that both the algal biomass could be used as an efficient biosorbents for the treatment of lead(II) bearing wastewater streams.     

Effects of environmental conditions on xylose reductase and xylitol dehydrogenase production by Candida guilliermondii

The effects of environmental conditions, namely initial pH (2.5–7.0) and temperature (25 and 35°C), on xylose reductase and xylitol dehydrogenase levels, as well as on xylitol production, were evaluated. Although the fermentative parameter values increased with an increase in pH and temperature (the maximum Y_P/s and Q _p were 0.75 g/g and 0.95 g/[L·h], respectively, both attained at pH 6.0, 35°C), the highest xylose reductase activities (nearly 900 1U/mg of protein) were observed at an initial pH varying from 4.0 to 6.0. Xylitol dehydrogenase was favored by an increase in both initial pH and temperature of the medium. The highest xylitol dehydrogenase specific activity was attained at pH 6.5 and 35°C (577 1U/mg of protein).     

Production of nisin by Lactococcus lactis in media with skimmed milk

Nisin is a bacteriocin that inhibits the germination and growth of Gram-positive bacteria. With nisin expression related to growth conditions of Lactococcus lactis subsp. lactis, the effects of growth parameters, media components, and incubation time were studied to optimize expression. L. lactis ATCC 11454 was grown (100 rpm at 30°C for 36 h) in both M17 and MRS standard broth media (pH 6.0–7.0) supplemented with sucrose (1.0–12.5 g/L), potassium phosphate (0.13 g/L), asparagine (0.5 g/L), and sucrose (0.24 g/L), and diluted 1:1 with liquid nonfat milk. Liquid nonfat milk, undiluted, was also used as another medium (9% total solids, pH 6.5). Nisin production was assayed by agar diffusion using Lactobacillus sake ATCC 15521 (30°C for 24 h) as the sensitive test organism. The titers of nisin expressed and released in culture media were quantified and expressed in arbitrary units (AU/L of medium) and converted into known concentrations of “standard nisin” (Nisaplin®, g/L). The detection of nisin activity was <0.01 AU/L in M17 and MRS broths, and 7.5 AU/L in M17 with 0.14% sucrose or 0.13% other supplements, and the activity increased to 142.5 AU/L in M17 diluted with liquid nonfat milk (1:1). The 25% milk added to either 25% M17 or 25% MRS provided the highest levels of nisin assayed.     

Biosorption of Chromium(III) by Biomass of Seaweed Sargassum sp. in a Fixed-Bed Column

This work aimed at modeling chromium biosorption using the biomass of seaweed Sargassum sp. in a fixed-bed column. The mathematical model used was obtained from the mass balance of the component in the liquid phase and in the biosorbent material. The effects of both axial dispersion in the column and the resistance to mass transfer in the solid were considered for the solution of the partial differential equations of the model, using the Galerkin method on finite elements. To represent the equilibrium data of the batch system the Langmuir isotherm were used. The chromium ion adsorption capacity of the seaweed Sargassum sp., at a temperature of 30°C and pH 3.5, was 2.61 mmol/g. The model performance was evaluated from experimental data obtained at 30°C for flow rates of 2, 6 and 8 mL/min. The parameters of the model, mass transfer and axial dispersion coefficients, were adjusted from these experimental data. The model proved adequate to describe chromium biosorption dynamics in fixed-bed columns.     

Biosorption of Pb(II) and Cd(II) ions by Agave sisalana (sisal fiber)

The present work proposes the use of Agave sisalana (sisal fiber) as an natural adsorbent for ions Pb(II) and Cd(II) biosorption from natural waters. The flame atomic absorption spectrometry was used for quantitative determination and study of the ions Pb(II) and Cd(II) adsorption on the solid phase. The Fourier transform infrared spectroscopy (FT IR) was used to investigate the sisal structure and the specific BET surface area was analyzed. The biosorption potential of sisal as biosorbent for the removal of the ions Pb(II) and Cd(II) from aqueous solution was investigate considering the followings parameters: pH, biomass amount and contact time. Langmuir and Freundlich isotherms were used to evaluate adsorption behavior of the ions on this solid phase. The results showed that sisal has a surface area to adsorption of 0.0233 m² g^{− 1}, and the OH and CO functional groups are the main involved in the biosorption. The best interpretation for the experimental data was given by Freundlich isotherm that proposes a monolayer sorption with a heterogeneous energetic distribution of active sites, accompanied by interactions between sorbed molecules. The maximum monolayer biosorption capacity was found to be 1.85 mg g^{− 1} for Cd (II) and 1.34 mg g^{− 1} for Pb (II) at pH 7 and 296 K. This phase solid can be used for biosorption of cadmium and lead in polluted natural waters.     

An epimerasic activity on galactose induced by xylose inKluyveromyces sp

Production of galactose epimerase by anKluyveromyces sp. isolated from Kefir (dairy product) was investigated in batch culture. The microorganism was cultured in media with 1% galactose, 1% xylose, or 0.5% xylose plus 0.5% galactose, in Erlenmeyer flasks shaken at 200 rpm and maintained at 30°C. After 48 h, the biomass was harvested by centrifugation and permeated with 80% ethanol. Permeated cells were suspended in 0.1M sodium phosphate buffer pH 6.5. A part of this suspension was shaken for 17h at 140 rpm. The supernatant, free of cells, was separated. Partial characterization ofKluyveromyces sp. epimerase was carried out in the cellular suspension and the supernatant solution. Enzymatic activity, using galactose as substrate, was measured. The product of this reaction was measured by the use of glucose oxidase. The results indicated: (1) there was a strong effect of xylose on induction of epimerase activity; (2) the epimerase obtained was independent of the energetic cell activity; (3) the epimerase activity in whole cells was similar to the activity obtained from the supernatant; (4) epimerase showed a typical substrate-inhibition curve and dependence on magnesium; and (5) the best pH range was between 5.5 and 6.5 and the optimal temperature was 30°C.     

Biosorption of Cr(VI) from Water Using Biomass of <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>: Central Composite Design for Optimization of Process Variables

The potential use of biomass of Aeromonas hydrophila for biosorption of chromium from aqueous solution was investigated. The variables (pH, initial Cr(VI) concentration, biomass dose, and temperature) affecting process were optimized by performing minimum number of experimental runs with the help of central composite design. The results predicted by design were found to be in good agreement (R ² = 99.1%) with those obtained by performing experiments. Multiple regression analysis shows that uptake decreases with increase in pH and biomass dose, whereas it increases with increase in temperature and concentration. The maximum removal of Cr(VI) predicted by contour and optimization plots was 184.943 mg/g at pH 1.5, initial Cr(VI) concentration 311.97 mg/L, temperature 60 °C, and biomass dose 1.0 g. The removal of Cr(VI) was governed by adsorption of Cr(VI) as well as its reduction into Cr(III), which further gets adsorbed. The sorption capacity of biomass was calculated from experimental data using Langmuir sorption model and was found to be 151.50 mg/g at 40 °C and pH 1.5, which is comparable to other biosorbents. In addition to this, Dubinin–Radushkevich model was applied, and it was found that nature of sorption was chemisorption.     

Preparation,characterization, and potential application of an immobilized glucose oxidase

A simple, one-step process, using 0.25Mp-benzoquinone dissolved in 20% dioxane at 50°C for 24 h was applied to the activation of polyacrylamide beads. The activated beads were reacted with glucose oxidase isolated fromAspergillus niger. The coupling reaction was performed in 0.1M potassium phosphate at pH 8.5 and 0–4°C for 24 h. The protein concentration was 50 mg/mL. In such conditions, the highest activity achieved was about 100 U/g solid. The optimum pH for the catalytic activity was shifted by about 1 pH unit in the acidic direction to pH 5.5. Between 35 and 50°C, the activity of the immobilized form depends on the temperature to a smaller extent than that of the soluble form. Above 50°C, the activity of immobilized glucose oxidase shows a sharper heat dependence. The enzyme-substrate interaction was not profoundly altered by the immobilization of the enzyme. The heat resistance of the immobilized enzyme was enhanced. The immobilized glucose oxidase is most stable at pH 5.5. The practical use of the immobilized glucose oxidase was tested in preliminary experiments for determination of the glucose concentration in blood sera.     

Biosorption of toxic metals using freely suspended Microcystis aeruginosa biomass

This paper describes the potential application of a freely suspended cyanobacterial biomass of Microcystis aeruginosa as a sorption material for toxic metals, cadmium (Cd) and lead (Pb) from aqueous solutions. In order to identify the most suitable conditions for removal of these elements (concentration range: 1–20 mg L^?1), the laboratory experiments were carried out during different incubation times (1–48 h) and under various temperatures (10–40°C), pH (5–9) and with or without light irradiance. Competitive biosorption of Cd and Pb was also investigated. We found that M. aeruginosa demonstrates high efficiency in removing both of the studied metals from aqueous solutions. Sorption of Pb occurred, however, more rapidly and effectively, and was less disturbed by changes in physico-chemical conditions. Under pH=7, 25°C and light, the removal rates after 3 h and 6 h of incubation, were 90–100% for Pb and 79.5–100% for Cd, respectively. The co-occurrence of the metals decreased the rate of metal biosorption. Pb was sequestered preferentially over Cd. From the results we conclude that freely suspended M. aeruginosa can constitute a promising low-cost, easy-producible biosorbent material for toxic metals in contaminated wastewater.      

Application of Artificial Neural Network and Particle Swarm Optimization for modelling and optimization of biosorption of Lead(II) and Nickel(II) from wastewater using dead cyanobacterial biomass

Removal of heavy metals through biosorption using biomass offers several advantages over other conventional techniques such as low cost, high efficiency, environmentally friendly, etc. In the present article, biosorption of Nickel(II) and Lead(II)was investigated using dried biomass of cyanobacterial consortium. OFAT (one-factor-at-a-time) analysis was used to assess the effect of input parameters on the removal of potentially toxic elements by varying initial metal ion concentration (2–10 mgL⁻¹), adsorbent dose (0.1–1.0 gL^-1), pH (for Pb(II): 2–6, for Ni(II): 2–8) and temperature (25°C–45°C) individually, at constant shaking speed of 150 ​rpm. Results showed that removal using biomass attained highest values in as short time as 15 ​min. The investigations also showed the removal is highly effective at lower initial concentrations of heavy metals. Maximum removal of Lead(II) (87.27 ​± ​1.75%) and Nickel(II) (92.57 ​± ​0.77%) was obtained at pH 6 and 45°C and at pH 7 and 25°C, respectively, within 15 ​min with 0.1 gL^-1 biomass. Both the Langmuir model and Freundlich model were seen to fit the equilibrium data. Further, Artificial Neural Network was used to model the biosorption process. Subsequently, Particle Swarm Optimization was applied to optimize the operating conditions for the removal of both the metals.     

Aspects of xylitol formation in sugarcane bagasse hydrolysate by Candida guillie rmondii in the presence of tetracycline

The biocon version of xylose intoxylitol using pH values of 4.0, 5.5 and 7.0 and tetracycline concentrations of 20 and 40 mg/L was carried out to verify the influence of these parameters on Candida guilliermondii metabolism for xylitol production. Experiments were performed with sugarcane bagasse hemicellulosi chydrolysate (48.5 g/L of xylose) in 125-mL Erlenmeyer flasks, at 30°C, 200 rpm, during 88 h. The results demostrated that the bioconversion of xylose into xylitol was significantly influenced by the pH. On the other hand, in media containing 20 or 40 mg/L of tetracycline, this bioconversion was not significantly affected. The best results of xylitol production were obtained in hemicellulosic hydrolysate without tetracycline, at pH 7.0 In these conditions, the maxim um specific growth rate was 0.014/h and the yield factor of xylitol and volumetric productivity were 0.85g/g and 0.70g/L/h respectively. Xylitol and cell growth occureed simultaneously.     

Biobleaching of nonwoody pulps using xylanase of Bacillus brevis BISR-062

The efficiency of xylanase of Bacillus brevis BISR-062 as a prebleaching agent was evaluated on three nonwoody pulps at two different pH values (7.0 and 8.5). Crude xylanase was found to have an optimum temperature and pH of 65–70°C and 7.0, respectively. The stability of the enzyme was determined at two pH values (7.0 and 8.0), and it lost approx 50% of its activity at both values within 2 h at 50°C. However, the enzyme was found to be effective as a prebleaching agent only with rice straw pulp. A maximum brightness gain of 6 points was obtained with this pulp at pH 7.0. The strength properties of the rice straw pulp at pH 7.0 also improved as the result of enzyme treatment.     

Characterization of bioconversion of fumarate to succinate by alginate immobilized Enterococcus faecalis RKY1

In this study, the immobilization characteristics of Enterococcus faecalis RKY1 for succinate production were examined. At first, three natural polymers—agar, κ-carrageenan, and sodium alginate—were tried as immobilizing matrices. Among these, sodium alginate was selected as the best gel for immobilization of E. faecalis RKY1. Efficient conditions for immobilization were established to be with a 2% (w/v) sodium alginate solution and 2-mm-diameter bead. The bioconversion characteristics of the immobilized cellsat various pH values and temperatures were examined and compared with those of free cells. The optimum pH and temperature of the immobilized cells were the same as for free cells, 7.0 and 38°C respectively, but the conversion ratio was higher by immobilization for all the other pH and temperature conditions tested. When the seed volume of the immobilized cells was adjusted to 10% (v/v), 30 g/L of fumarate was completely converted tosuccinate (0.973 g/g conversion ratio) after 12 h. In addition, the immobilized cells maintained a conversion ratio of >0.95 g/g during 4wk of storageat 4°C in a 2% (w/v) CaCl₂ solution. In repetitive bioconversion experiments, the activity of the immobilized cells decreased linearly according to the number of times of reuse.     

Intracellular release of recombinant green fluorescent protein (gfp uv ) from Escherichia coli

The recombinant green fluorescent protein (gfp _uv ) was expressed by Escherichia coli DH5-α cells transformed with the plasmid pGFPuv. The gfp _uv was selectively permeabilized from the cells in buffer solution (25 mM Tris-HCl, pH 8.0), after freezing (−70°C for 15 h), by four freeze (−20°C)/thaw cycles interlaid by sonication. The average content of released gfp _uv (experiment 2) was 7.76, 34.58, 39.38, 12.90, and 5.38%, for the initial freezing (−70°C) and the first, second, third and fourth freeze/thaw cycles, respectively. Superfusion on freezing was observed between −11°C and −14°C, after which it reached −20°C at 0.83°C/min.     

Purification and Characterization of Thermostable Chitinase from <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> SK-1

Chitinase was purified from the culture medium of Bacillus licheniformis SK-1 by colloidal chitin affinity adsorption followed by diethylamino ethanol-cellulose column chromatography. The purified enzyme showed a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular size and pI of chitinase 72 (Chi72) were 72 kDa and 4.62 (Chi72) kDa, respectively. The purified chitinase revealed two activity optima at pH 6 and 8 when colloidal chitin was used as substrate. The enzyme exhibited activity in broad temperature range, from 40 to 70°C, with optimum at 55°C. It was stable for 2 h at temperatures below 60°C and stable over a broad pH range of 4.0–9.0 for 24 h. The apparent K _m and V _max of Chi72 for colloidal chitin were 0.23 mg ml⁻¹ and 7.03 U/mg, respectively. The chitinase activity was high on colloidal chitin, regenerated chitin, partially N-acetylated chitin, and chitosan. N-bromosuccinamide completely inhibited the enzyme activity. This enzyme should be a good candidate for applications in the recycling of chitin waste.     

An improved method for extraction of β-carotene from blakeslea trispora

An improved method for the extraction of β-carotene from Blakeslea trispora is described. The fermentation broth was steamed at 121°C for 15 min, and the liquid was centrifuged at 5000g for 20 min. β-Carotene was removed from the biomass by extraction with absolute ethanol at a ratio of 1:100 at 30°C for 2 h in a rotary shaker incubator at 300 rpm. The carotenoid pigment was completely removed from the cells after three repeated extractions. The removal of β-carotene from B. trispora was higher during the first stage (75%) whereas in the other stages it was very slow.     

Evaluation of solid and submerged fermentations for the production of cyclodextrin glycosyltransferase by Paenibacillus campinasensis H69-3 and characterization of crude enzyme

Cyclodextrin glycosyltransferase (CGTase) is an enzyme that produces cyclodextrins from starch by an intramolecular transglycosylation reaction. Cyclodextrins have been shown to have a number of applications in the food, cosmetic, pharmaceutical, and chemical industries. In the current study, the production of CGTase by Paenibacillus campinasensis strain H69-3 was examined in submerged and solid-state fermentations. P. campinasensis strain H69-3 was isolated from the soil, which grows at 45°C, and is a Gramvariable bacterium. Different substrate sources such as wheat bran, soybean bran, soybean extract, cassava solid residue, cassava starch, corn starch, and other combinations were used in the enzyme production. CGTase activity was highest in submerged fermentations with the greatest production observed at 48–72 h. The physical and chemical properties of CGTase were determined from the crude enzyme produced from submerged fermentations. The optimum temperature was found to be 70–75°C, and the activity was stable at 55°C for 1 h. The enzyme displayed two optimum pH values, 5.5 and 9.0 and was found to be stable between a pH of 4.5 and 11.0.