Reusable Membranes Research Articles

Effective and reusable oil/water separation membranes based on modified polysulfone electrospun nanofiber mats

Abstract Membrane technology is the most promising process for oil/water separation operation if the hydrophilicity, fouling and reusability properties could be improved. In this study, novel effective and reusable membrane for oil–water separation process is introduced based on modification of polysulfone (PSF) electrospun nanofiber mats. The modification process was achieved by incorporation of NaOH nanoparticles inside the PSF nanofibers, and formation of a thin layer from a polyamide polymer on the surface of the electrospun mat. Typically, solutions composed of PSF and NaOH (twelve solutions were prepared based on different PSF concentrations; 15, 18 and 20 wt%, and various NaOH content; 1.5, 1.7 and 2.5 wt%) have been electrospun, then the dried nanofiber mats were treated by m-phenylenediamine and 1,3,5-benzenetricarbonyl chloride to form polyamide thin layer on the surface of the mats. The results indicated that incorporation of NaOH and the formed polyamide could decrease the water contact angle from ∼130° to 13° for the nanofiber mats obtained from 20 wt% PSF solutions containing 1.7 wt% sodium hydroxide. Interestingly, the membrane having the lowest contact angle could separate oil–water mixture for three successive cycles with complete removal of the oil at a relatively high water flux; 5.5 m 3 /m 2 day. Overall, simplicity of the manufacturing technique, and effectiveness and reusability of the produced nanofiber mats open new avenue for the introduced electrospun mats as promising membranes for the oil–water separation process.

Two ubiquitin-like conjugation systems that mediate membrane formation during autophagy

In autophagy, the autophagosome, a transient organelle specialized for the sequestration and lysosomal or vacuolar transport of cellular constituents, is formed via unique membrane dynamics. This process requires concerted actions of a distinctive set of proteins named Atg (autophagy-related). Atg proteins include two ubiquitin-like proteins, Atg12 and Atg8 [LC3 (light-chain 3) and GABARAP (γ-aminobutyric acid receptor-associated protein) in mammals]. Sequential reactions by the E1 enzyme Atg7 and the E2 enzyme Atg10 conjugate Atg12 to the lysine residue in Atg5, and the resulting Atg12-Atg5 conjugate forms a complex with Atg16. On the other hand, Atg8 is first processed at the C-terminus by Atg4, which is related to ubiquitin-processing/deconjugating enzymes. Atg8 is then activated by Atg7 (shared with Atg12) and, via the E2 enzyme Atg3, finally conjugated to the amino group of the lipid PE (phosphatidylethanolamine). The Atg12-Atg5-Atg16 complex acts as an E3 enzyme for the conjugation reaction of Atg8; it enhances the E2 activity of Atg3 and specifies the site of Atg8-PE production to be autophagy-related membranes. Atg8-PE is suggested to be involved in autophagosome formation at multiple steps, including membrane expansion and closure. Moreover, Atg4 cleaves Atg8-PE to liberate Atg8 from membranes for reuse, and this reaction can also regulate autophagosome formation. Thus these two ubiquitin-like systems are intimately involved in driving the biogenesis of the autophagosomal membrane.

In this issue

AbstractCheaper cytokine production for stem cell culturesBasic fibroblast growth factor (FGF‐2) is a cytokine that is used to keep embryonic stem cells in an undifferentiated state. The application is however limited because of its high price. In this issue, Thomas Scheper (Hannover, Germany) and collaborators present a fast and efficient process for the production and purification of FGF‐2 from recombinant Escherichia coli cultures with reusable membrane adsorbers. After achieving a high expression level of FGF‐2 in fed‐batch cultivation, a new combination of cation‐exchange membrane chromatography and heparin–sepharose‐affinity chromatography is employed to purify the protein. In a polishing step using a novel anion‐exchange membrane chromatography, endotoxins and DNA are removed. The described process is suitable as a low‐cost preparation of bioactive FGF‐2 at bench‐scale, which can be applied for the production of other cytokines.……………29http://dx.doi.org/10.1002/elsc.201100045magnified imageTurning waste in to gold: Cellulase production from palm oil mill effluentCellulases have numerous industrial applications. For example in the food and beverage industry, these enzymes are used for the extraction of fruit juices, for coffee processing, improving beer filtration and modification of wine aroma. As cellulases hydrolyze cellulosic materials into sugars that can be fermented into bioethanol, it has an increasing relevance for biofuel and bioenergy production. In Malaysia, palm oil mill effluent (POME) is a waste product in palm oil production. It is rich in carbohydrates, proteins, lipids, minerals, cellulose, hemicelluloses and lignin and is a sustainable supply of biomass for cheap cellulase production. In this issue, authors from Nibong Tebal, Malaysia, present a comprehensive review on cellulases, their application and production with a focus on using POME from Malaysia as a substrate.……………7http://dx.doi.org/10.1002/elsc.201000228magnified imageAzo dye biodegradation by a bacterial consortiumde los Cobos‐Vasconcelos et al., Eng. Life Sci. 2012, 12, 39–48.Industrially produced azo dyes are designed to resist fading and are not easy to degrade. Inexpensive biological treatments present a practical solution for wastewater treatment in the textile industry, because they can degrade potentially harmful compounds. In this issue, Nora Ruiz‐Ordaz et al. from Mexico show the biodegradation of the sulfonated azo dyes, Acid Orange 7 (AO7) and Acid Red 88 (AR88), by a bacterial consortium isolated from water and soil samples. An aerobically operated two‐stage rectangular packed‐bed biofilm reactor (PBR) was constructed and characterized. Eight bacterial strains were isolated from the biofilm attached to the porous support of the PBR. Interestingly, both dyes present the sole carbon and nitrogen sources used by the microbial consortium.……………39http://dx.doi.org/10.1002/elsc.201000227magnified image

Cytokine production using membrane adsorbers: Human basic fibroblast growth factor produced by Escherichia coli

AbstractBasic fibroblast growth factor (FGF‐2) is a multifunctional cytokine that regulates various cellular processes both in vitro and in vivo. FGF‐2 is extensively used in embryonic stem cell cultures since it can maintain the cells in an undifferentiated state. However, the high price of FGF‐2 has limited its application in stem cell research. Here we present a fast and efficient process for the purification of FGF‐2 from recombinant Escherichia coli cultures using reusable membrane adsorbers. A high expression level of FGF‐2 (42 mg/g dry cell) was achieved by fed‐batch cultivation of E. coli BL21(DE3). A new combination of cation exchange membrane chromatography and heparin‐sepharose affinity chromatography was used for the purification of the protein. A novel anion exchange membrane chromatography was used in the polishing step to remove endotoxins and DNA. In this new process, about 200 mg soluble FGF‐2 was yielded from 1.9 L culture broth with a purity of 98%. The purified protein was identified to be endotoxin‐free and bioactive. It was successfully tested to keep primate embryonic stem cell and human‐induced pluripotent stem cell pluripotent. Our approach, in which a controlled cultivation process is combined with an optimized fast and versatile downstreaming process, is suitable for low‐cost preparation of bioactive FGF‐2 at bench‐scale and may be beneficial to the effective production of other cytokines.

Validation of a Low-Cost Human Papillomavirus Genotyping Assay Based on PGMY PCR and Reverse Blotting Hybridization with Reusable Membranes

The genotyping of human papillomaviruses (HPV) is essential for the surveillance of HPV vaccines. We describe and validate a low-cost PGMY-based PCR assay (PGMY-CHUV) for the genotyping of 31 HPV by reverse blotting hybridization (RBH). Genotype-specific detection limits were 50 to 500 genome equivalents per reaction. RBH was 100% specific and 98.61% sensitive using DNA sequencing as the gold standard (n = 1,024 samples). PGMY-CHUV was compared to the validated and commercially available linear array (Roche) on 200 samples. Both assays identified the same positive (n = 182) and negative samples (n = 18). Seventy-six percent of the positives were fully concordant after restricting the comparison to the 28 genotypes shared by both assays. At the genotypic level, agreement was 83% (285/344 genotype-sample combinations; κ of 0.987 for single infections and 0.853 for multiple infections). Fifty-seven of the 59 discordant cases were associated with multiple infections and with the weakest genotypes within each sample (P < 0.0001). PGMY-CHUV was significantly more sensitive for HPV56 (P = 0.0026) and could unambiguously identify HPV52 in mixed infections. PGMY-CHUV was reproducible on repeat testing (n = 275 samples; 392 genotype-sample combinations; κ of 0.933) involving different reagents lots and different technicians. Discordant results (n = 47) were significantly associated with the weakest genotypes in samples with multiple infections (P < 0.0001). Successful participation in proficiency testing also supported the robustness of this assay. The PGMY-CHUV reagent costs were estimated at $2.40 per sample using the least expensive yet proficient genotyping algorithm that also included quality control. This assay may be used in low-resource laboratories that have sufficient manpower and PCR expertise.

A versatile oxygenator and perfusion system for magnetic resonance studies

A compact, reusable membrane oxygenator has been constructed for the perfusion of cultured cells and isolated organs. While the oxygenator was designed to be compatible with nuclear magnetic resonance (NMR) spectroscopy studies, it can also be used for any experiment which requires warming and oxygenation of perfusates. For the NMR studies, the oxygenator can be positioned at the opening of the magnet bore which allows oxygenation and warming of the perfusate immediately prior to delivery to the tissue, therefore eliminating problems with heat or oxygen loss which may occur with the long perfusion lines. (c) 1996 John Wiley & Sons, Inc.

Review article: Hepatitis B and dialysis

The incidence of hepatitis B virus (HBV) infection in dialysis populations has declined over recent decades, largely because of improvements in infection control and widespread implementation of HBV vaccination. Regardless, outbreaks of infection continue to occur in dialysis units, and prevalence rates remain unacceptably high. For a variety of reasons, dialysis patients are at increased risk of acquiring HBV. They also demonstrate different disease manifestations compared with healthy individuals and are more likely to progress to chronic carriage. This paper will review the epidemiology, modes of transmission and diagnosis of HBV in this population. Prevention and treatment will be discussed, with a specific focus on strategies to improve vaccination response, new therapeutic options and selection of patients for therapy.

Improved Artificial Feeding System for Rearing the Whitefly Bemisia argentifolii (Homoptera: Aleyrodidae)

The artificial rearing system for Bemisia argentifolii Bellows and Perring has been improved by the selection of an autoclavable, reusable membrane, reduction of the sucrose concentration, choice of yeast extract, use of an antifungal agent in the petri dish chamber, choice of surface sterilization agent, egg storage, and maintenance of high humidity in the chamber during the entire nymphal development. We can now produce small numbers of adult whiteflies of both sexes on these chambers, confirming the utility of these improvements. We also reared two Bemisia tabaci A-strain to adults and several Trialeurodes vaporariorum nymphs to the 3rd and 4th instar on the improved feeding system.

Bovine chromaffin cells: Studies on the biosynthesis of phospholipids in chromaffin granules

We have studied the biosynthesis of chromaffin granules by labelling primary cultures of bovine chromaffin cells with either [ 35S]methionine or various precursors for lipids. After labelling the cells were subjected to subcellular fractionation including density gradient centrifugation. After [ 35S]methionine significant label (mainly represented by labelled chromogranin A) was found in the soluble proteins of chromaffin granules, whereas the membranes were relatively little labelled. However incorporation into membrane bound dopamine β-hydroxylase and cytochrome b-561 could be demonstrated. Neither of the used lipid precursors ([ 3H]glycerol, [ 3H]choline, [ 3H]palmitic acid or [ 3H]arachidonic acid) was incorporated to any significant extent into the soluble components of chromaffin granules. Thus there is no evidence that this secretory compartment contains any lipids or acylated proteins. Incorporation of lipid precursors into the membranes of chromaffin granules was apparently low. After short chases labelled lysolecithin was not present in these organelles. However with prolonged chase times labelled lysolecithin apparently appeared in chromaffin granules irrespective of whether the cells were stimulated or not. We can conclude that the reusable membranes of chromaffin granules have a very low lipid turnover. Lysolecithin is not transferred into these organelles during biosynthesis but is formed in them during their long life span. This formation of lysolecithin is independent of stimulation of these cells and therefore unlikely to be involved in exocytosis.

Successful 20-hour storage of the canine liver by continuous hypothermic perfusion

Summary Fifteen canine livers were stored by means of continuous hypothermic (10°C) perfusion using homologous serum as the perfusate. The organs were transplanted as allografts. Succinate and glucose were added as substrates and other additives included hydrocortisone, heparin, insulin, and Keflin. Flow rate was adjusted to give a portal vein pressure of 6 to 8 cm of H 2 O and hepatic artery pressure of 80 mm Hg. Of the initial seven attempts to store the liver for 20 hrs only one organ sustained life for 1 week and it exhibited severe damage. The remaining six died within 12 to 48 hrs from a hemorrhagic diathesis. Two of two organs were held successfully for 7 brs using an identical storage procedure; one of these animals survived 8.5 months. Storage conditions were then altered. The perfusate pH was adjusted to 7.0 (37°C) instead of 7.25 (37°C) which was used in the initial nine attempts. Also, substrate level was supplemented after 6 to 10 hrs of perfusion. The six animals receiving these latter organs after 20-hr storage were walking 2 to 4 hrs after surgery and they exhibited no bleeding. Four of the six organs were considered successfully stored for the 20-hr period. A reusable all-Silastic perfusion system was developed for the above studies. The perfusion circuit consists of a series of Silastic tubings and incorporates a simple reusable membrane oxygenator.