[Show abstract][Hide abstract] ABSTRACT: A new nanoporous biomatrix originated from bacterial resources has been chosen for urease immobilization. Urease has been immobilized on synthesized bacterial cellulose nanofiber since this enzyme has a key role in nitrogen metabolism.
ATCC 10245 has been cultivated for synthesis of a nanofiber with the diameter of 30–70 nm. Different cultivation processes in the aspect of time and cultivation medium conditions were chosen to study the performance of immobilized enzyme on four types of bacterial cellulose nanofibers (BCNs). Urease immobilization into the nanofiber has been done in two steps: enzyme adsorption and glutaraldehyde cross-linking. The results showed that the immobilized enzymes were relatively active and highly stable compared to the control samples of free enzymes. Optimum pH was obtained 6.5 and 7 for different synthesized BCNs, while the optimum temperature for immobilized urease was 50°C. Finding of the current experiment illustrated that the immobilized enzyme in optimum condition lost its initial activity by 41% after 15 weeks.
Preview · Article · Dec 2015 · International Journal of Polymer Science
[Show abstract][Hide abstract] ABSTRACT: article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Peer-review under responsibility of the scientific committee of Eurosensors 2014 Abstract In this paper, a rapid and sensitive method for colorimetric sensing of hydrogen sulfide (H 2 S) in aqueous solutions is illustrated. A novel biosensor is developed based on one-shot adsorption of chemically-modified cytochrome c (cyt c) onto gold nanorods (Au NRs). Here by reacting H 2 S with protein heme centre, the protein conformation changed. The conformational changes occurring in the protein altered the spectral characteristics by change in the dielectric properties of Au NRs. The limit of detection (LOD) and sensitivity of Au NRs / cyt c biosensor were evaluated by using UV– visible spectroscopy. According to the experiments, it is revealed that sulfide anions can be detected at a concentration of 2.0 μM (0.75 ppb) by Au NRs / cyt c biosensor. This simple and cost-effective sensing platform provides a rapid and convenient detection for sulfide anions at concentrations far below the hazardous limit.
Full-text · Article · Dec 2014 · Procedia Engineering
[Show abstract][Hide abstract] ABSTRACT: Aim:Liposome Encapsulated Haemoglobin (LEH) has been already introduced as an artificial oxygen carrier nanoparticle with the potential substitution ca-pability for red blood cells. However, the synthesis process of current LEH yields low haemoglobin (Hb) loading due to the instability of LEH encapsulation. Therefore, the surface coating of LEH with a stable polymer would be beneficial.
Methods:Bovine Hb is encapsulated by hydrating a dry-film lipid (comprising 0.4 mM Cholesterol and 0.6 mM Dipalmitoylphosphatidylcholine) through a phos-phate buffer solution blended with glutamine antioxidant. In the next step, the size of synthetized particles is decreased to nano-range using a high-pressure homogenizer. The synthesis process is modified by the insertion of polyethylene oxide (PEO) through the solution during the cascade of homogenization.
Results:Coated LEH with 2.5, 5, 10 and 40% w/w of PEO present an increase of the total Hb loading yield of 27 ± 3, 33 ± 2, 39 ± 2 and 45 ± 2% respectively, compared to non-coated LEH with a loading yield of 20 ± 1%. On the contrary, the size of coated LEH increase gradually from 107 ± 3 nm to 228 ± 3 nm by raising the concentration of PEO from 2.5 to 40% w/w while non-coated LEH shows the size of 98 ± 3 nm.
Conclusions: Coating of LEH with PEO during its synthesis process increases its stability, and subsequently, enhances its efficiency by elevating the total Hb loading yield. However, the effect of the increase of particle size should be fur-ther investigated.
[Show abstract][Hide abstract] ABSTRACT: We present a simple method for direct detection of hydrogen sulfide (H2S) in an aqueous solution. This method represents a novel biosensor based on metalloprotein cytochrome c (cyt c) with the localized surface plasmon resonance of gold nanoparticles (AuNPs). For this purpose, we develop a new approach based on attaching chemically-modified cyt c onto AuNPs. Here, by reacting H2S with protein heme center, its conformation changes in the locality of the heme moiety. The conformational changes occurring in the protein alter the spectral characteristics by changing the dielectric properties of AuNPs. The conformational changes of cyt c induced by the H2S interaction are characterized by the UV-visible absorption spectroscopy and the circular dichroism technique. The limit of the detection and sensitivity of the AuNPs/cyt c biosensor are evaluated by using UV-visible spectroscopy. According to the experiments, it is revealed that H2S can be detected at a concentration of 4.0 μM (1.3 ppb) by the fabricated AuNPs/cyt c biosensor. In addition, the sensor retains activity and gives reproducible results after storage in 4°C for 60 d. This simple and cost-effective sensing platform provides a rapid and convenient detection for H2S at concentrations far below the hazardous limit.
No preview · Article · Jul 2014 · Chinese Physics Letters
[Show abstract][Hide abstract] ABSTRACT: Despite cyanidation currently being the conventional gold recovery process, researchers are looking for alternative methods for the recovery of gold from its sources without using cyanide. The current work attempts to study the recovery of gold from copper anode slime by means of a novel process utilizing magnetite nanoparticles (MNPs).In this process, MNPs were first synthesized byco-precipitation method, and thecharacterization of the product was then carried out using theX-ray diffraction (XRD), transmission electron microscopy (TEM),andvibration sample magnetometer (VSM) methods.Thiourea solution was employed as leachant. All the gold content of copper anode slime was dissolved in thiourea solution and a positive complex of gold and thiourea was obtained as a result. At a pH value higher than the pH of point of zero charge (PZC), the nanoparticles (NPs) were added to the gold solution. The gold complex adsorbed on the NPs due to their negative surface charge. At the last stage, ammonia was added to the gold-attached NP suspension and gold was consequently precipitated in metallic form. The results obtained from the method indicate the high efficiency of the methodfor the recovery of gold from copper anode slime.
[Show abstract][Hide abstract] ABSTRACT: In recent years, biosurfactants due to wide applications in chemical, petroleum, food and pharmaceutical industries, have been widely considered by researchers. Biosurfactants are produced by a series of microorganisms, so it is important to screen culture medium and operating conditions in miniaturized bioreactors prior to scaling up to large bioreactors.In this study, using a kind of miniaturized bioreactor called ventilation flask, optimal production conditions, including filling volume and shaking frequency to produce a surfactin-type biosurfactant by Bacillus subtilis ATCC 6633, were examined. Moreover, the effect of oxygen transfer rate (OTR) on the surfactin production was investigated according to Amoabediny and Büchs model. The results indicated that the maximum biomass and biosurfactant yield which obtained under optimal conditions (filling volume of 15 mL and shaking frequency of 300 rpm) were evaluated 0.3 g/L/h and 0.0485 g/L/h, respectively. Also, at the same conditions, the amount of surface tension decreased from 60.5 mN/m to 31.7 mN/m and the maximum oxygen transfer rate (OTRmax) obtained as 0.01 mol/L/h.
[Show abstract][Hide abstract] ABSTRACT: In a process for cleaning hydrocarbonaceous residues, including residual petroleum from laboratory made oil-contaminated vessels, several previously isolated bacteria from Ilam and Paydar oil reservoirs, were used. The isolated strains were compared with the standard sample of Acinetobacter calcoaceticus PTCC 1318 from Persian Type Culture Collection (PTCC). This gram-negative bacterium grows on a variety of different substrates as sole carbon and energy sources, including crude oil, soy oil and ethanol. It is oxidase-negative, non-motile and strictly aerobic. Among the isolated strains, two autochthonous strains were found to produce an extracellular emulsifying agent when grown in Mineral Salt Medium containing soy oil, ethanol or local crude oil. The crude emulsifier of PTCC1318, Paydar-4 and Ilam-1 were concentrated from the cell-free culture fluid by ammonium sulfate precipitation to yield 1.89 g, 1.78 g and 1.69 g of bioemulsan, respectively. Although measuring the surface tension (ST) is not very applicable procedure in case of bioemulsan, but in order to prove this theory, ST was conducted.Further analysis of purified emulsion was performed to prove the molecular structure by Carbon13 Nuclear Magnetic Resonance, Proton1Nuclear Magnetic Resonance and Fourier Transform Infrared Radiation methods. These investigations showed that the molecular weight of emulsion produced by species isolated from Ilam and Paydar crude oil reservoirs are comparable with Acinetobacter calcoaceticus PTCC 1318.
Full-text · Article · Apr 2012 · Iranian Journal of Environmental Health Science & Engineering
[Show abstract][Hide abstract] ABSTRACT: A novel and economical method was used to optimize bacterial growth and bioemulsan production. Acinetobacter calcoaceticus PTCC 1641 was applied in an innovated synthetic medium comprised whey and mineral salt medium (MSM) in ratio of 1:1 in a shaken flask bioreactor. The optimum inoculum size, shaking frequency rate and filling volume (V(L)) using ventilation flasks were investigated that resulted in 5 vol.%, 300 rpm and 15 ml), respectively. The surface tension decreased around 48% during bioemulsan production. Due to determine bioemulsan properties, the reliability of blood agar method was confirmed as well.
No preview · Article · Dec 2010 · Bioresource Technology
[Show abstract][Hide abstract] ABSTRACT: Cell culture systems are fundamental tools in biotechnology. A major limitation of these systems is the lack of high throughput systems for screening purposes. This bottleneck might be alleviated through employing of miniaturized systems. Miniaturized or small-scale bioreactors could be handled in parallel, use small quantities of material and will be enable to explore a wider range of process conditions. The use of small-scale bioreactors has the potential to increase the process development rate, to reduce research cost and also have advantages such as control, automation and scalability to various degrees. Various types of miniaturized shaken bioreactors and their economical effects on process are summarized and compared in this study.
[Show abstract][Hide abstract] ABSTRACT: The extraction of protein by continuous liquid–liquid extraction was investigated in a rotating disc contactor (RDC) and a rotating sieved disc contactor (RSDC) with and without stators. Hydrodynamics and mass transfer performance for reversed micellar extraction of lysozyme in RDC/RSDC I and RSDC II have been investigated. The dispersed phase holdup has increased with the increase of rotor speed. Pratt's equation was used for calculating the characteristic velocity. An inverse relation was observed between the characteristic velocity and rotor speed. The estimated overall mass transfer coefficient was increased by increasing the rotor speed. For an extraction column, the overall hydrodynamics and mass transfer performance can be judged by a volumetric utilization factor. At high rotor speeds, volumetric utilization factor for RSDCs is higher than that of RDC. The RSDC II has been successfully applied in reversed micellar extraction of protein.
Full-text · Article · May 2009 · Chemical Engineering Science
[Show abstract][Hide abstract] ABSTRACT: Spinal cord injury is very complicated, as there are factors in the body that inhibit its repair. Although regeneration of the mammalian central nervous system (CNS) was once thought to be impossible, studies over the past two decades have shown that axonal growth after spinal cord injury can occur when provided with the correct substratum. Traditionally, tissue transplantation or peripheral nerve grafting are used to repair damaged or diseased regions of the CNS, but donor shortage and immunological problems associated with infectious disease are often encountered. Fortunately, recent advances in neuroscience, cell culture, and biomaterials provide optimistic future using new treatments for nerve injuries.Biomaterial scaffold creates substrate within which cells are instructed to form a tissue or an organ in a highly controlled way. The principal function of a scaffold is to direct cell behavior such as migration, proliferation, differentiation, maintenance of phenotype, and apoptosis by facilitating sensing and responding to the environment via cell–matrix and cell–cell communications. Therefore, having such abilities provides scaffolds seeded with a special type of cell as an important part of tissue engineering and regenerative medicine which spinal cord regeneration is an example of. Nevertheless, the vast number of biodegradable synthetic and natural biopolymers makes choosing the right one very difficult. In this review article, it was tried to provide an inclusive survey of biopolymers seeded with Schwann cells (SCs) to be used for axonal regeneration in the nervous system.
Full-text · Article · Dec 2008 · Neurochemistry International
[Show abstract][Hide abstract] ABSTRACT: A study on TCF (totally chlorine-free) bleachability of kraft pulps from bagasse was carried out by treating them with a commercial lipase from the Aspergillus niger fungus, followed by a sequence of oxygen and peroxide bleaching stages. The effect of the enzymatic stage on bleachability has been studied and compared with that of xylanase (produced from Trichoderma reesei) and control pulps (processed without enzyme addition). A final brightness of 71-72% ISO was achieved after complete bleaching. Direct bleaching affects both pulp brightness (by 2.5-1.9% ISO) and delignification (by 0.28 and 0.20%, on oven-dry pulp) immediately after the enzymatic stage. The bleachability of these pulps was superior to that of the control during all peroxide stages, under peroxide charges between 3 and 9%. Bleaching selectivity was determined by changes in intrinsic viscosity. Generally, higher bleachability and higher bleaching selectivity of the xylanase-treated pulps caused a maximal gain in pulp brightness (or bleach boosting, as the main objective of xylanase application), which could be achieved only after the first and second peroxide bleaching stages, followed by a substantial diminishing by the end of the sequence.
No preview · Article · Jul 2008 · Cellulose Chemistry and Technology