The use of bacteria immobilized in tubular membrane reactors for heavy metal recovery and degradation of chlorinated aromatics

Microbial treatments of waste water can be done in membrane reactors. A membrane installed outside the reactor is used to separate bacteria from the treated effluent.

A new membrane reactor concept is presented. The separation membrane is introduced in the reactor and not outside as in a normal one. The membrane plays the role of a separator of two streams and is used at the same time as the immobilizing support for the bacteria.

The reactor keeps the bacteria active via a specific nutrient stream that is provided on one side of the membrane. The bacteria grow in and on the membrane where they form an active biofilm. The bacteria can treat the effluent on one side and can be kept active via the nutrient stream at the other side without contamination of the effluent by the nutrient.

In this work, the performance of the BICMER (Bacteria Immobilized Composite MEmbrane Reactor) is demonstrated via treatments of effluents containing heavy metals or organic xenobiotics.

For heavy metal removal Alcaligenes eutrophus CH34 bacteria were used. These bacteria induce a metal bioprecipitation process that results in the formation of crystalline metal carbonates, which are recovered on a separate column in the reactor. In this way metals can be recovered without disturbing the biofilm on the membrane. Metals such as Cd, Zn, Cu, Pb and Y can be reduced to less than 50 ppb. The metals Co, Ni, Pd and Ge are reduced to below 100 ppb.

For organic xenobiotics Alcaligenes eutrophus AE1308 bacteria or other strains (depending on the xenobiotic to be degraded) were used. This strain degrades the xenobiotic 3-chlorobenzoate (Cba) and 2,4-dichlorophenoxyacetic acid to CO₂, H₂O and chloride). Concentrations of 3 mM Cba could be reduced to less than 0.1 mM. For other toxic organic compounds, different biodegrading strains need to be used.     

Biocatalytic Langmuir–Blodgett assemblies based on penicillin G acylase

The recently developed ‘protective plate’ method offers the possibility to include protein layers into a Langmuir–Blodgett (LB) assembly without contact of protein molecules with the air–water interface thus avoiding their denaturation. In the present work, this technique was applied for the deposition of biocatalysts with active layers of penicillin G acylase (PGA), an enzyme widely used for medicine production. Easy selection of LB and adsorbed layers resulted in the creation of appropriate environments for the preservation of PGA functions. Two structures were tested regarding such performances as the enzymatic activity value and the level of PGA detachment in aqueous solutions. It was shown that they satisfy the requirements for biocatalytic applications. The enzymatic activity of PGA monolayer incorporated into the film reached 25–30% of the activity value of the equivalent amount of protein in the solution, which is a good result for an immobilized enzyme. Further modification of the deposition procedure resulted in increasing the effective activity per unit of the substrate surface due to adsorption of a thicker protein layer in one cycle. Probably, a three-dimensional frame-like structure was formed, which allowed the substrate molecules to penetrate into the film. The enzymatic activity of such films per unit of the substrate surface was 20–25 times higher than that of the assemblies with one adsorbed monolayer. Finally, the method is proposed of biocatalytic LB assembly deposition onto flexible supports of practically unlimited length without the exposure of protein layer to air medium.     

Preparation and chiral recognition in HPLC of cellulose 3,5-dichlorophenylcarbamates immobilized onto silica gel

The 3,5-dichlorophenylcarbamates (2) of cellulose bearing a small amount of 3-(triethoxysilyl)propyl residues were synthesized by a one-pot process and immobilized onto a silica gel through intermolecular polycondensation of the triethoxysilyl groups. The obtained cellulose derivatives were characterized by (1) H NMR and elemental analysis (EA), and their recognition abilities were evaluated by high-performance liquid chromatography (HPLC). The cellulose derivatives containing about 1-5% of the 3-(triethoxysilyl)propyl residue were efficiently immobilized with a high chiral recognition ability. The immobilized chiral packing materials (CPMs) could be used with the eluents containing chloroform and tetrahydrofuran (THF), which cannot be used with the conventional coated-type chiral packing materials. By using these eluents, the chiral recognition for many racemates was improved.     

Highly enantioselective bioreduction of ethyl 3-oxohexanoate

Seven wild-type microorganism strains were used to reduce ethyl 3-oxohexanoate to ethyl (R)-3-hydroxyhexanoate. Free cells of Kluyveromyces marxianus and Aspergillus niger led to higher than 99% of conversion with higher than 99% ee. After immobilization in calcium alginate spheres, cells of K. marxianus exhibited high enantioselectivity (>99% ee) and conversion level (99%) within 24 h even if substrate was added at concentration of 10 g/L (62 mM).     

Synthesis,characterization, and immobilization of nickel(II) tetradentate Schiff-base complexes on clay as heterogeneous catalysts for the oxidation of cyclooctene

Nickel(II) tetradentate Schiff-base complexes of N,N′-(bis(pyridin-2-yl)formylidene)ethane-1,2-diamine (L1), N,N′-(bis(pyridin-2-yl)formylidene)cyclohexane-1,2-diamine (L2), N,N′-(bis(pyridin-2-yl)formylidene)benzene-1,2-diamine (L3), N,N′-(bis(pyridin-2-yl)formylidene)meso-stilben-1,2-diamine (L4), and N,N′-(bis(pyridin-2-yl)formylidene)propane-1,3-diamine (L5) were synthesized, characterized, and immobilized on sodium montmorillonite. The complexes were characterized by IR spectroscopy, diffuse reflectance spectra (DRS), and atomic absorption spectroscopy (AAS). IR and DRS data of the heterogeneous catalysts show that the Ni(II) complexes were physically entrapped within the sodium montmorillonite clay. The supported complexes show good catalytic activity for the epoxidation of cyclooctene using tert-butylhydroperoxide (TBHP) as oxygen source in acetonitrile. The Ni-catalyzed oxidation proceeds with 62.3% selectivity for epoxidation with 69% conversion for supported [Ni(L5)].     

Gold and Silver Nanoparticles Supported on Metal-organic Frameworks: a Highly Active Catalyst for Three-component Coupling Reaction

Engineering metal-organic frameworks(MOF) for heterogeneous catalysts have been of extreme interest since they have large pore size within the crystalline framework and well defined pore architecture. Ni-containing MOF Ni₂(3,5-Pydc)₂(H₂O)₈·2H₂O(1·H₂O) was prepared by solvothermal method from 3,5-pyridinedicarboxylic acid, D-camphoric acid and Ni(NO₃)₂·6H₂O in dimethylformamide(DMF)/water(volume ratio 2:1). And two gold and silver functionalized 1·H₂O catalysts were prepared by impregnation method. Catalysts 2.53%Au/MOF and 4.23%Ag/MOF were in-depth characterized by single crystal X-ray diffraction, powder X-ray diffraction(PXRD), thermogravimetric analysis(TGA), transmission electron microscopy(TEM), and inductively coupled plasma-atomic emission spectroscopy(ICP-AES). Their catalytic performance was examined in one-pot synthesis of structurally divergent propargylamines via three component coupling of aldehyde, alkyne, and amine(A³) in 1,4-dioxane. The results show that the catalysts all displayed high reactivities, and a selectivity of 100% for propargylamines. Catalysts 2.53%Au/MOF and 4.23%Ag/MOF have proved to be applicable to a wide range of substrates. Catalysts 2.53%Au/MOF and 4.23%Ag/MOF can be easily recycled and used repetitively at least 3 times with a slight drop in activity. These features render the catalysts particularly attractive in the practice of propargylamines synthesis in an environmentally friendly manner.     

Novel Porous Polyethersulfone Beads as Matrix to Immobilize Comamonas testosteroni sp.bdq06 in Quinoline Biodegradation

Novel matrix beads for the immobilization of strain Comamonas testosteroni sp. bdq06 to degrade quinoline were fabricated from polyethersulfone(PES). The beads have an average size of 3 mm and a surface dense layer of 20 microns. To help adhesion and proliferation of bacterial cells, the surfaces of the PES beads were etched, and numerous holes about 1.5 micrometers in diameter were generated as tunnels for cell colonizing in the larger internal cavities of about 5 micrometers in diameter. The quinoline degradation was remarkably enhanced by the cells immobilized in PES beads compared with that by the free cells at pH 5.0 or 10.0 and a temperature of 40 ℃. The enhanced degradation of quinoline was contributed to the biofilm on the surface of PES beads, resulting in the significant reduction of retention time from 9 h to 2 h. Furthermore, the beads remain intact after the ultrasonic treatment of them for 30 min or recycling 50 times, indicating that they have excellent mechanical strength, flexibility and swelling capacity. Thus, PES beads have great potential to be matrix for the cell immobilization in bioaugmentation.     

Amberlite XAD-4 functionalized with m-phenylendiamine: Synthesis, characterization and applications as extractant for preconcentration and determination of rhodium (III) in water samples by Inductive Couple Plasma Atomic Emission Spectroscopy (ICP-AES)

A new chelating resin is prepared by coupling Amberlite XAD-4 with metaphenylendiamine through an azo spacer, characterized (elemental analysis, IR and thermogravimetric analysis (TGA)) and studied for preconcentration Rh (III) using Inductive Couple Plasma Atomic Emission Spectroscopy (ICP-AES) for rhodium monitoring. The optimum pH value for sorption of the metal ion was 6.5 (recovery 100%). The sorption capacity was found 0.256 mmol g^− 1 of resin for Rh (III). The method has a detection limit and limit of quantification of 0.05 and 0.08 μg mL^− 1 at pH 6.5, respectively. The chelating resin can be reused for 10 cycles of sorption-desorption without any significant change in sorption capacity. A recovery of 100% was obtained for the metal ion with 1.5 M HCl as eluting agent. The equilibrium adsorption data of Rh (III) on modified resin were analyzed by Langmuir and Freundlich models. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of adsorption. The positive value of the enthalpy change (2.48 kJ/mol) indicates that the adsorption is an endothermic process. The method was applied for rhodium ions determination from tap water sample.     

PVA-Hydrogel Entrapped <Emphasis Type="Italic">Candida Guilliermondii</Emphasis> for Xylitol Production from Sugarcane Hemicellulose Hydrolysate

Viable cells of Candida guilliermondii were immobilized by inclusion into polyvinyl alcohol (PVA) hydrogel using the freezing–thawing method. Entrapment experiments were planned according to a 2³ full factorial design, using the PVA concentration (80, 100, and 120 g L⁻¹), the freezing temperature (−10, −15, and −20 °C), and the number of freezing-thawing cycles (one, three, and five) as the independent variables, integrated with three additional tests to estimate the errors. The effectiveness of the immobilization procedure was checked in Erlenmeyer flasks as the pellet capability to catalyze the xylose-to-xylitol bioconversion of a medium based on sugarcane bagasse hemicellulosic hydrolysate. To this purpose, the yield of xylitol on consumed xylose, xylitol volumetric productivity, and cell retention yield were selected as the response variables. Cell pellets were then used to perform the same bioconversion in a stirred tank reactor operated at 400 rpm, 30 °C, and 1.04 vvm air flowrate. At the end of fermentation, a maximum xylitol concentration of 28.7 g L⁻¹, a xylitol yield on consumed xylose of 0.49 g g⁻¹ and a xylitol volumetric productivity of 0.24 g L⁻¹ h⁻¹ were obtained.     

Silk-Fiber Immobilized Lipase-Catalyzed Hydrolysis of Emulsified Sunflower Oil

Lipase was immobilized in silk fibers through glutaraldehyde cross-linking to a maximum loading of 59 U/g silk-fiber and the immobilized lipase was utilized for the hydrolysis of sunflower oil (Helianthus annuus). The hydrolytic activity of the lipase, which was poor in biphasic oil in water system, was increased significantly when the sunflower oil was emulsified in aqueous medium. The hydrolytic activities of the immobilized lipase were 48.73 ± 1.26 U, 36.11 ± 0.96 U, and nil when the substrate sunflower oil was used as emulsion created by a rhamnolipid biosurfactant, Triton X100, and ultrasonication, respectively. Although the efficiency of the immobilized lipase was less than 12% than the corresponding free lipase, the immobilized lipase could be reused for the biosurfactant-mediated hydrolysis of sunflower oil up to third cycle of the reaction. The yield of the fatty acids in the second, third, and fourth cycles were 49.45%, 22.91%, and 5.09%, respectively, of the yield obtained in the first cycle.