High-density Membrane Research Articles

Production of polyhydroxyalkanoates and astaxanthin from lignocellulosic biomass in high cell density membrane bioreactor

Microbial-derived bioplastics are receiving more attention and are a potential option for ecological sustainability. Lignocellulosic biomass is the ultimate resource for the production of second-generation biofuels and biochemicals. In this study, lignocellulosic biomass (corn cob) was first pretreated and hydrolyzed to produce fermentable sugars. Then, polyhydroxyalkanoates (PHA) and astaxanthin were produced through batch and cell retention cultures of two strains, Bacillus megaterium ALA2 and Paracoccus sp. LL1 using corn cob hydrolysate as a carbon source. Higher cell and PHA concentrations (101.7 g/L and 57.6 g/L, respectively) with a PHA productivity of 1.07 g/L/h were obtained by B. megaterium ALA2, but Paracoccus sp. LL1 could co-produce PHA and astaxanthin. PHA and astaxanthin concentrations were significantly increased by cell retention culture of Paracoccus sp. LL1 in high cell density membrane bioreactor compared to batch culture (9.04 and 13.1-folds, respectively). In addition, PHA and astaxanthin productivities by cell retention culture of Paracoccus sp. LL1 increased to 0.579 g/L/h and 0.385 mg/L/h, respectively, which were 4.02 and 10.1-folds higher than those of batch culture. Based on gas chromatography, 1H nuclear magnetic resonance, and Fourier transform infrared analysis, B. megaterium ALA2 produced a homopolymer of poly(3-hydroxybutyrate), whereas poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with 7.84 mol% of 3-hydroxyvalerate was accumulated by Paracoccus sp. LL1. This study demonstrates that bioplastic PHA and high value-added astaxanthin can be economically produced from lignocellulosic biomass as an inexpensive renewable resource. This is the first report on the enhanced co-production of PHA and astaxanthin from lignocellulosic biomass in a membrane bioreactor.

Rational design of high power density “Blue Energy Harvester” pressure retarded osmosis (PRO) membranes using artificial intelligence-based modeling and optimization

The challenge in harvesting Salinity Gradient Power (SGP) through pressure retarded osmosis (PRO) requires design of high power density (PD) membranes and optimized process for operation. Recent studies show that for a feasible PRO operation the minimum net PD should be around 50 W/m2. In this study, a data-driven approach has been adopted for designing optimum membranes as well as operating conditions. 200 papers, from last decade, were extensively reviewed and 34 experimental research articles were shortlisted for possible data mining, to predict water flux (WF) and PD. Comprehensive screened/pre-processed data related to both membrane and process (16 inputs) was obtained from 18 articles amounting to 339 data points. Two artificial neural network (ANN) models were explored (i) Levenberg-Marquardt (ANN-LM), and (ii) Bayesian Regularization (ANN-BR) along with a combination of three different activation functions i.e., hyperbolic tangent sigmoid transfer function (Tan-Sigmoid), logarithmic sigmoid transfer function (Log-Sigmoid) in the input and output layers. Out of the six resulting combinations, the best performing combination was found to be Tan-Sigmoid activation function in both layers with ANN-BR model having an R2 value of 0.97 for WF and 0.98 for PD. Membrane properties like the type of membrane, thickness, and water permeability coefficient were found to be the major contributing factors for the prediction of WF while for PD, operating conditions such as applied pressure were found to play the major contributing factor (10–16 %). Optimization results yield a maximum WF of 147 LMH and PD of 87 W/m2. These results were compared with the solution diffusion (S-D) model.

Airbrushed nanofibrous membranes to control stem cell infiltration in 3D‐printed scaffolds

AbstractExtrusion‐based 3D printing of polymeric biomaterials has emerged as a promising approach for the fabrication of complex tissue engineering constructs. However, the large pore and feature size lead to low cell seeding efficiency and limited control of spatial distribution of cells within the scaffolds. We developed hybrid scaffolds that are composed of 3D‐printed layers and airbrushed fibrous membranes. Airbrushing time was adjusted to fabricate low (L), medium (M), and high (H) density membranes to effectively control stem cell infiltration. When two distinct populations of stem cells were seeded from top or bottom of the scaffolds, scaffolds composed of LLL membranes showed gradual mixing of the cells with depth, whereas LHL membranes led to two distinct regions of cells separated by the H membrane. Our results demonstrate that fibrous membranes incorporated within 3D‐printed layers enable user‐defined and spatially controlled cell compositions within hybrid scaffolds.

Structure Optimization of a High-Temperature Oxygen-Membrane Module Using Finite Element Analysis

The oxygen transport membrane (OTM) is a high-density ion-conducting ceramic membrane that selectively transfers oxygen ions and electrons through the pressure differential across its layers. It can operate at more than 800 °C and serves as an economical method for gas separation. However, it is difficult to predict the material properties of the OTM through experiments or analyses because its structure contains pores and depends on the characteristics of the ceramic composite. In addition, the transmittance of porous ceramic materials fluctuates strongly owing to their irregular structure and arbitrary shape, making it difficult to design such materials using conventional methods. This study analyzes the structural weakness of an OTM using CAE software (ANSYS Inc., Pittsburgh, PA, USA). To enhance the structural strength, a structurally optimized design of the OTM was proposed by identifying the relevant geometric parameters.

Enhancing performance of biocarriers facilitated gravity-driven membrane (GDM) reactor for decentralized wastewater treatment: Effect of internal recirculation and membrane packing density

This study aims to investigate the effect of internal recirculation and membrane packing density on the performance (water quality, membrane performance, and microbial community) of a biocarriers facilitated gravity-driven membrane (GDM) reactor under intermittent aeration condition. The results revealed that the presence of internal recirculation in the GDM reactors could effectively improve water quality (especially increasing nitrogen removal) and membrane performance (especially reducing cake layer resistance) compared to those without internal recirculation. In addition, compared to a high packing density membrane module (1150 m2/m3), a lower packing density membrane module (290 m2/m3) benefited to improve 15% of nitrogen removal and 44% of permeate flux due to the effective aeration scouring effect and less-limited eukaryotic activity, as well as reduce 20% of total treatment cost. In addition, the presence and absence of internal recirculation could lead to dissimilar microbial community compositions of the biofilms in the GAC layers and on the membrane surfaces. However, the membrane packing density could play an insignificant effect on the microbial community compositions of the biofilms in the GDM reactors with internal recirculation.

Complete Membrane Fractionation of 3T3-L1 Adipocytes.

Fractionation techniques can facilitate the isolation of intracellular organelles containing insulin-sensitive glucose transporter isoform 4 (GLUT4), which is mobilized from GLUT4 storage vesicles in fat and muscle cells in response to insulin. This protocol for the full membrane fractionation of 3T3-L1 adipocytes results in five distinct fractions. A heavy membrane-containing pellet is produced and then further separated into the plasma membrane, mitochondrial and nuclear, and high-density membrane fractions. The initial supernatant is subjected to a series of centrifugation steps to isolate the low-density membrane fraction, which contains the majority of the insulin-sensitive pool of GLUT4; the supernatant produced in this step is the soluble fraction. The distribution of GLUT4 in fractions from insulin-stimulated versus untreated cells is assessed via immunoblotting.

Pressure Retarded Osmosis (PRO): Past experiences, current developments, and future prospects

Pressure Retarded Osmosis (PRO) has attracted worldwide attention with respect to its salinity gradient energy production potential, and low energy desalination applications. PRO processes, which use Seawater Reverse Osmosis (SWRO) brine as draw solutions, have a higher potential of being applied to any new, and existing membrane based seawater desalination systems, as an energy production and/or conservation process. Hydraulic pressure is applied on a high salinity draw solution, and the hydraulic pressure of the high salinity draw solution can be kept relatively constant during operation, even though the volumetric flow rate is to be increased. Therefore, the draw side of the PRO process can be considered near-isobaric, in most cases. The harvested Gibbs free energy of mixing, and the volumetric expansion can explain this near-isobaric behavior of the draw side in the PRO process. Thus, PRO can be used to multiply the internal energy of the draw solution with respect to the ratio of the permeated water flux. Even though PRO has very high theoretical potential for energy production and/or recovery, there are several shortcomings, which should be answered before the realization of the scale up applications, such as; thermodynamic process optimization, high power density membranes, and high efficiency hydraulic pressure conversion and recovery systems. This review gives detailed information about the PRO process including; (1) theoretical background, (2) membranes for PRO, (3) experimental and large scale applications, and (4) economic feasibility of PRO applications.

Influence of material characteristics on the structure and properties of high-density polyethylene microporous membranes

Five PE resins with different material characteristics were chosen to fabricate microporous membranes based on a melt-stretching mechanism.

Cytoskeletal Components Define Protein Location to Membrane Microdomains*

The plasma membrane is an important compartment that undergoes dynamic changes in composition upon external or internal stimuli. The dynamic subcompartmentation of proteins in ordered low-density (DRM) and disordered high-density (DSM) membrane phases is hypothesized to require interactions with cytoskeletal components. Here, we systematically analyzed the effects of actin or tubulin disruption on the distribution of proteins between membrane density phases. We used a proteomic screen to identify candidate proteins with altered submembrane location, followed by biochemical or cell biological characterization in Arabidopsis thaliana. We found that several proteins, such as plasma membrane ATPases, receptor kinases, or remorins resulted in a differential distribution between membrane density phases upon cytoskeletal disruption. Moreover, in most cases, contrasting effects were observed: Disruption of actin filaments largely led to a redistribution of proteins from DRM to DSM membrane fractions while disruption of tubulins resulted in general depletion of proteins from the membranes. We conclude that actin filaments are necessary for dynamic movement of proteins between different membrane phases and that microtubules are not necessarily important for formation of microdomains as such, but rather they may control the protein amount present in the membrane phases.

High Yield Non-detergent Isolation of Photosystem I-Light-harvesting Chlorophyll II Membranes from Spinach Thylakoids: IMPLICATIONS FOR THE ORGANIZATION OF THE PS I ANTENNAE IN HIGHER PLANTS

Styrene-maleic acid copolymer was used to effect a non-detergent partial solubilization of thylakoids from spinach. A high density membrane fraction, which was not solubilized by the copolymer, was isolated and was highly enriched in the Photosystem (PS) I-light-harvesting chlorophyll (LHC) II supercomplex and depleted of PS II, the cytochrome b6/f complex, and ATP synthase. The LHC II associated with the supercomplex appeared to be energetically coupled to PS I based on 77 K fluorescence, P700 photooxidation, and PS I electron transport light saturation experiments. The chlorophyll (Chl) a/b ratio of the PS I-LHC II membranes was 3.2 ± 0.9, indicating that on average, three LHC II trimers may associate with each PS I. The implication of these findings within the context of higher plant PS I antenna organization is discussed.

Experimental research on the high-density polyethylene anti-permeable membrane of waste-water pools

Since a high-density polyethylene membrane has good mechanical properties and stable chemical properties, it is widely used in all kinds of anti-permeable layers. But for a sewage pool of a drilling engineering in the western desert oil field, it is not only facing a high temperature and drying environment, but also quite a complex drilling fluid composition. Yet an experimental study system on application has not set up in China. According to the working environment of the high-density polyethylene membrane, a series of aging tests are carried out in the paper. Measured the change value of the high-density polyethylene membrane, mechanical properties are expressed directly the aging properties of high-density polyethylene membranes.

Mesenchymal stem cells and collagen patches for anterior cruciate ligament repair.

To investigate collagen patches seeded with mesenchymal stem cells (MSCs) and/or tenocytes (TCs) with regards to their suitability for anterior cruciate ligament (ACL) repair. Dynamic intraligamentary stabilization utilizes a dynamic screw system to keep ACL remnants in place and promote biological healing, supplemented by collagen patches. How these scaffolds interact with cells and what type of benefit they provide has not yet been investigated in detail. Primary ACL-derived TCs and human bone marrow derived MSCs were seeded onto two different types of 3D collagen scaffolds, Chondro-Gide(®) (CG) and Novocart(®) (NC). Cells were seeded onto the scaffolds and cultured for 7 d either as a pure populations or as "premix" containing a 1:1 ratio of TCs to MSCs. Additionally, as controls, cells were seeded in monolayers and in co-cultures on both sides of porous high-density membrane inserts (0.4 μm). We analyzed the patches by real time polymerase chain reaction, glycosaminoglycan (GAG), DNA and hydroxy-proline (HYP) content. To determine cell spreading and adherence in the scaffolds microscopic imaging techniques, i.e., confocal laser scanning microscopy (cLSM) and scanning electron microscopy (SEM), were applied. CLSM and SEM imaging analysis confirmed cell adherence onto scaffolds. The metabolic cell activity revealed that patches promote adherence and proliferation of cells. The most dramatic increase in absolute metabolic cell activity was measured for CG samples seeded with tenocytes or a 1:1 cell premix. Analysis of DNA content and cLSM imaging also indicated MSCs were not proliferating as nicely as tenocytes on CG. The HYP to GAG ratio significantly changed for the premix group, resulting from a slightly lower GAG content, demonstrating that the cells are modifying the underlying matrix. Real-time quantitative polymerase chain reaction data indicated that MSCs showed a trend of differentiation towards a more tenogenic-like phenotype after 7 d. CG and NC are both cyto-compatible with primary MSCs and TCs; TCs seemed to perform better on these collagen patches than MSCs.

Activation of Lyn Tyrosine Kinase through Decreased Membrane Cholesterol Levels during a Change in Its Membrane Distribution upon Cell Detachment

Cellular membranes, which can serve as scaffolds for signal transduction, dynamically change their characteristics upon cell detachment. Src family kinases undergo post-translational lipid modification and are involved in a wide range of signaling events at the plasma membrane, such as cell proliferation, cell adhesion, and survival. Previously, we showed the differential membrane distributions among the members of Src family kinases by sucrose density gradient fractionation. However, little is known about the regulation of the membrane distribution of Src family kinases upon cell detachment. Here, we show that cell detachment shifts the main peak of the membrane distribution of Lyn, a member of Src family kinase, from the low density to the high density membrane fractions and enhances the kinase activity of Lyn. The change in Lyn distribution upon cell detachment involves both dynamin activity and a decrease in membrane cholesterol. Cell detachment activates Lyn through decreased membrane cholesterol levels during a change in its membrane distribution. Furthermore, cholesterol incorporation decreases Lyn activity and reduces the viability of suspension cells. These results suggest that cell detachment-induced Lyn activation through the change in the membrane distribution of Lyn plays an important role in survival of suspension cells.

Characterization of new bacterial catabolic genes and mobile genetic elements by high throughput genetic screening of a soil metagenomic library

A mix of oligonucleotide probes was used to hybridize soil metagenomic DNA from a fosmid clone library spotted on high density membranes. The pooled radio-labeled probes were designed to target genes encoding glycoside hydrolases GH18, dehalogenases, bacterial laccases and mobile genetic elements (integrases from integrons and insertion sequences). Positive hybridizing spots were affiliated to the corresponding clones in the library and the metagenomic inserts were sequenced. After assembly and annotation, new coding DNA sequences related to genes of interest were identified with low protein similarity against the closest hits in databases. This work highlights the sensitivity of DNA/DNA hybridization techniques as an effective and complementary way to recover novel genes from large metagenomic clone libraries. This study also supports that some of the identified catabolic genes might be associated with horizontal transfer events.

Covalent-organic framework as a template to assemble carbon nanotubes into a high-density membrane: computational demonstration

Carbon nanotube (CNT) membranes have a wide range of important technological applications; however, the fabrication of high-density CNT membranes is challenging. Using molecular simulation, we demonstrate that a covalent-organic framework (COF-8) can act as a template promoting (9, 9) CNTs to assemble into a homogeneous high-density membrane. Surprisingly, the templated assembly is unique for (9, 9) CNTs and not observed for smaller or larger CNTs. The microscopic analysis based on the potential of mean force reveals that the highly selective assembly of (9, 9) CNTs into COF-8 is thermodynamically favorable, in contrast to other CNTs. This proof-of-concept computational study proposes a bottom-up strategy to produce high-density CNT membranes, and has a significant implication in CNT applications.

Investigating the elastic deformation of wood–plastic composites at cold temperature using the bubble inflation technique

In recent years, there has been increasing interest in the development of wood–plastic composites (WPC) for use as building materials. Using wood as natural reinforcement in composite materials, instead of mineral reinforcements, has several advantages such as low density, low cost, and less abrasive finish. The natural reinforcements are also non-toxic and recyclable. The wide variety of WPCs makes it difficult to discuss the performance of these composites. In this research, the bubble inflation technique, introduced by Joye et al., is used to study the behaviour of biocomposite materials in cold temperatures. The results of experiments with high-density polyethylene and WPC membranes with 20, 30, 40, 50 and 60 wt% of wood fibre, under the combined effect of temperature and pressure are presented. The membranes are tested under the maximum pressure of 18 psi within the temperature range of −50C to +50°C with 25°C increments.

Luteinizing Hormone Receptors are Confined in Mesoscale Plasma Membrane Microdomains Throughout Recovery from Receptor Desensitization

We examined the involvement of membrane microdomains during human luteinizing hormone (LH) receptor recovery from receptor desensitization after removal of bound hormone. Lateral motions of individual desensitized LH receptors expressed on the surface of Chinese hamster ovary cells and transient association of these receptors with detergent-resistant membrane (DRM) microdomains isolated using isopycnic sucrose gradient ultracentrifugation were assessed. Single particle tracking experiments showed untreated individual LH receptors to be confined within cell-surface membrane compartments with an average diameter of 199 ± 17 nm and associated with membrane fractions characteristic of bulk plasma membrane. After brief exposure to human chorionic gonadotropin (hCG), LH receptors remained for several hours desensitized to hCG challenge. Throughout this period, significantly increased numbers of LH receptors were confined within smaller diameter (<120 nm) membrane compartments and associated with DRM fragments of characteristically low density. By 5 h, when cells again produced cAMP in response to hCG, unoccupied LH receptors were found in larger 169 ± 22 nm diameter cell-surface membrane compartments and >90 % of LH receptors were again found in high-density membrane fragments characteristic of bulk plasma membrane. Taken together, these results suggest that, during recovery from LH receptor desensitization, LH receptors are both located with DRM lipid environments and confined within small, mesoscale (80-160 nm) cell-surface compartments. This may reflect hormone-driven translocation of receptors into DRM and formation there of protein aggregates too large or too rigid to permit effective signaling. Once bound hormone is removed, receptor structures would have to dissociate before receptors can again signal effectively in response to hormone challenge. Moreover, such larger protein complexes would be more easily constrained laterally by membrane structural elements and so appear resident in smaller cell-surface compartments.

Complex and Multidimensional Lipid Raft Alterations in a Murine Model of Alzheimer's Disease

Various animal models of Alzheimer's disease (AD) have been created to assist our appreciation of AD pathophysiology, as well as aid development of novel therapeutic strategies. Despite the discovery of mutated proteins that predict the development of AD, there are likely to be many other proteins also involved in this disorder. Complex physiological processes are mediated by coherent interactions of clusters of functionally related proteins. Synaptic dysfunction is one of the hallmarks of AD. Synaptic proteins are organized into multiprotein complexes in high-density membrane structures, known as lipid rafts. These microdomains enable coherent clustering of synergistic signaling proteins. We have used mass analytical techniques and multiple bioinformatic approaches to better appreciate the intricate interactions of these multifunctional proteins in the 3xTgAD murine model of AD. Our results show that there are significant alterations in numerous receptor/cell signaling proteins in cortical lipid rafts isolated from 3xTgAD mice.

Down-regulation of c-Cbl by Morphine Accounts for Persistent ERK1/2 Signaling in δ-Opioid Receptor-expressing HEK293 Cells

Opioids display ligand-specific differences in the time course of ERK1/2 signaling. Whereas full agonists, like etorphine, induce only transient activation of ERK1/2, the partial agonist morphine mediates persistent stimulation of mitogenic signaling. Here we report that in stably delta-opioid receptor (DOR)-expressing HEK293 (HEK/DOR) cells, the transient nature of etorphine-induced ERK1/2 signaling is due to desensitization of epidermal growth factor (EGF) receptor-mediated activation of the Ras/Raf-1/ERK1/2 cascade. Desensitization of ERK1/2 activity by etorphine is associated with down-regulation of EGF receptors, an effect mediated by the ubiquitin ligase c-Cbl. In contrast, chronic morphine treatment failed to desensitize EGF receptors, resulting in unimpeded ERK1/2 signaling. The failure of morphine to desensitize ERK1/2 signaling is mediated by persistent activation of c-Src, which induces degradation of c-Cbl. The role of c-Src in opioid-specific ERK1/2 signaling is further demonstrated by pretreatment of the cells with PP2 and SKI-I as well as overexpression of a dominant negative c-Src mutant (c-Src(dn)) or a c-Src-resistant c-Cbl mutant (CblY3F), both of which facilitate desensitization of ERK1/2 signaling by morphine. Conversely, overexpression of c-Src as well as down-regulation of c-Cbl by small interfering RNA results in persistent etorphine-induced stimulation of ERK1/2 activity. Subcellular fractionation experiments finally attributed the ability of morphine to persistently activate c-Src to its redistribution from Triton X-100-insensitive membrane rafts to DOR and EGF receptor containing high density membrane compartments implicated in ERK1/2 signaling. These results demonstrate that agonist-specific differences in the temporal and spatial pattern of c-Src activation determine the kinetics of DOR-mediated regulation of ERK1/2 signaling.

Expression of caveolin‐1 in hepatic cells increases oxidized LDL uptake and preserves the expression of lipoprotein receptors

Oxidized LDL (OxLDL) that are positively associated with the risk of developing cardiovascular diseases are ligands of scavenger receptor-class B type I (SR-BI) and cluster of differentiation-36 (CD36) which can be found in caveolae. The contribution of these receptors in human hepatic cell is however unknown. The HepG2 cell, a human hepatic parenchymal cell model, expresses these receptors and is characterized by a very low level of caveolin-1. Our aim was to define the contribution of human CD36, SR-BI, and caveolin-1 in the metabolism of OxLDL in HepG2 cells and conversely the effects of OxLDL on the levels/localization of these receptors. By comparing mildly (M)- and heavily (H)-OxLDL metabolism between control HepG2 cells and HepG2 cells overexpressing CD36, SR-BI, or caveolin-1, we found that (1) CD36 increases M- and H-OxLDL-protein uptake; (2) SR-BI drives M-OxLDL through a degradation pathway at the expense of the cholesterol ester (CE) selective uptake pathway; (3) caveolin-1 increases M- and H-OxLDL-protein uptake and decreases CE selective uptake from M-OxLDL. Also, incubation with M- or H-OxLDL decreases the levels of SR-BI and LDL-receptor in control HepG2 cells which can be overcome by caveolin-1 expression. In addition, OxLDL move CD36 from low to high buoyant density membrane fractions, as well as caveolin-1 in cells overexpressing this protein. Thus, hepatic caveolin-1 expression has significant effects on OxLDL metabolism and on lipoprotein receptor levels.