Lab 8: Membrane Filtration - Biology

Lab 8: Membrane Filtration - Biology

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is there poop in your water?

Safe drinking water is a problem for nearly 1 billion people worldwide. Diarrhea caused by drinking contaminated water is still a leading cause of illness and death among infants and children in the developing world. Over 1000 children die every day as a result of diseases that cause diarrhea. More children die from diarrheal illnesses such as cholera, dysentery, and typhoid fever than from HIV/AIDS and malaria combined.

This is primarily caused by fecal contamination of open water. Certain members of the Enterobacteriaceae family such as Escherichia coli, Klebsiella pneumoniae, and Enterobacter aerogenes are relatively abundant in feces and easy to detect. Therefore, these organisms are used as an indicator species when testing water for fecal contamination. These bacteria are gram-negative, facultative anaerobes that are able to ferment lactose to produce large amounts of acid and gas. Bacteria that possess these qualities are called coliform. Once the presence of coliform bacteria is detected in a water source, further tests are done to determine if more dangerous fecal-borne pathogens are present.

Membrane filtration is a technique for testing water samples. Afterward, the filter is applied to the surface of Endo agar plates and incubated for 24 hours. Endo agar is a selective media that encourages gram-negative bacterial growth and inhibits gram-positive growth. It also contains lactose for fermentation and a dye to indicate pH changes. Coliform colonies typically appear with a gold/metallic sheen.

After incubation, all metallic colonies are counted and are used to calculate the number of coliform colonies/volume filtered using the following formula:

[frac{ ext{total coliforms}}{ ext{volume filtered}} onumber]

A countable plate has 20-200 coliform colonies.

Complete the following experiment working as a pair:

1. Label 2 Endo agar plates.

2. Filter 100 mL. of control and sample water that you have been provided through a filter (filter needs to be changed between each sample).

3. Using sterile forceps, place the filter on the filter housing.

4. Clamp the top half of the assembly.

5. Pour the water inside and open the vacuum.

6. Once all the water is passed through close the vacuum, remove the top half of the filter.

7. With sterile forceps, remove the filter and place it in the middle of the Endo agar plate.

Sartorius Membrane Filters, a Membrane for Nearly Every Need

Cellulose nitrate or mixed cellulose ester membrane filters are indicated for many general laboratory applications where a membrane with a high non-specific adsorption is suitable. They are hydrophilic, have high flow rates thanks to their symmetric structure and are compatible with aqueous solutions (pH 4 to 8), hydrocarbons and several other organic solvents. The cellulose nitrate membranes are available in different pore sizes from 0.2 μm to 8 μm.

  • Hydrophilic
  • High flow rates
  • Aqueous and organic solvent compatible
  • For particle retention and cell capture in aqueous solutions or air
  • Available in multiple diameters and pore sizes

Save on all kinds of products.

Water and Wastewater Testing

Quality Equipment for Accurate Results

Fisher Scientific offers essential water and wastewater testing equipment, including spectrophotometers, refractometers, turbidity meters and flasks.

Our selection of spectrophotometers includes devices that help you maximize productivity, like the Thermo Scientific™ NanoDrop™ Microvolume UV-Vis Spectrophotometer, as well as low-budget options for use in schools, like the Fisher Scientific™ Educational Spectrophotometer.

Similarly, we offer both hand-held and benchtop refractometers, like the Mettler Toledo™ Refractor 30 PX Portable Refractometer that can store up to 1,100 results, and the Mettler Toledo Excellence RM Digital Benchtop Refractometer that gives you greater flexibility and a host of additional features.

For quick and accurate turbidity readings, we offer a range of meters from Thermo Scientific, LaMotte and Lovibond. And for measuring and mixing samples, we have a variety of flasks from leading brands like Pyrex and Buchner, including shock resistant, borosilicate, PVC-coated and heavy-duty options.

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Laboratory Filtration

Millipore ® membranes have supported laboratory filtration in academic, pharmaceutical, and industrial sectors since the 1950s. We provide a range of membrane chemistries including MF-Millipore ® mixed cellulose esters, Durapore ® PVDF, Millipore Express ® PLUS polyethersulfone, as well as hydrophilic and hydrophobic PTFE.

An extensive selection of glass, stainless steel, and plastic filter holders for use with cut disc membrane filters for liquid and gas filtration, including syringe filter holders, in-line filter housings, and filter holders for vacuum and pressure filtration.

High performance sterile and nonsterile syringe filters offered in a variety of membrane materials and pore sizes, tailored for sample preparation for HPLC, UHPLC, ion chromatography, dissolution testing, and other analyses.

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Membranes for Filtration

Recommended when maximum recovery is important. Durapore&trade PVDF Membranes: 0.45&mu Pore Size provide high flow rates and throughput, low extractables, broad chemical compatibility and low protein binding. Available in diameters ranging from 13mm to 142mm.

MilliporeSigma&trade MF-Millipore&trade Mixed Cellulose Ester Membranes with Grid: 0.45&mum Pore Size

Designed for a wide range of analytical and research applications. MF-Millipore&trade Mixed Cellulose Ester Membranes, 0.45&mum pore size are available in a range of diameters. Composed of mixed cellulose membrane in black or white with a plain or gridded surface.

MilliporeSigma&trade Nylon Hydrophilic Membrane Filters

Filtration of aqueous or organic solutions

MilliporeSigma&trade Durapore&trade PVDF Membrane Filters: 0.22&mu Pore Size

Recommended when maximum recovery is important. Durapore&trade PVDF Membranes: 0.22&mu Pore Size provide high flow rates and throughput, low extractables, broad chemical compatibility and low protein binding. Available in diameters ranging from 13mm to 142mm.

MilliporeSigma&trade MF-Millipore&trade Mixed Cellulose Ester Membranes: 5.0&mum Pore Size

Designed for a wide range of analytical and research applications. MF-Millipore&trade Mixed Cellulose Ester Membranes, 5.0&mum pore size are available in a range of diameters. Composed of plain, white mixed cellulose membrane.

MilliporeSigma&trade MF-Millipore&trade Mixed Cellulose Ester Membranes: 0.80&mum Pore Size

Designed for air monitoring, bioassays, dairy microbiology, particle monitoring and particle removal. MF-Millipore&trade Mixed Cellulose Ester Membranes, 0.80&mum pore size are available in a range of diameters. Composed of mixed cellulose membrane in black or white with a plain or gridded surface.

GVS Magna&trade Nylon Membrane Filters

Plain white nylon membranes offer low extractables, high uniformity

Sartorius Gridded Sterile Cellulose Nitrate Membrane Filters: 0.45&mum

Ensure quality control in microbiological filtering. Sartorius Gridded Sterile Cellulose Nitrate Membrane Filters, 0.45&mum are single-packed membranes with colored grids for colony counting, particle testing and microscopy. The 0.45&mum pore size is made in accordance with ISO 7704. Choose from two diameters and quantities in a range of filter/grid color combinations.

MilliporeSigma&trade MF-Millipore&trade Mixed Cellulose Ester Membranes: 0.22&mum Pore Size

Designed for a wide range of analytical and research applications. MF-Millipore&trade Mixed Cellulose Ester Membranes, 0.22&mum pore size are available in a range of diameters. Composed of plain, white mixed cellulose membrane.

MilliporeSigma&trade Express&trade PLUS Membrane Filters

Plain white polyethersulfone membranes provide ultrafast filtration for a variety of applications

Cytiva Whatman&trade Nylon Membranes

Flexible and durable for easier handling. Cytiva Nylon Membranes are naturally hydrophilic, eliminating need for wetting agents and prewetting when filtering aqueous solutions.

Cytiva Whatman&trade Polydisc In-line Filter

Cytiva Whatman&trade Polyethersulfone (PES) Membrane Filters

Whatman polyethersulfone (PES) membrane filters from Cytiva’s Life Sciences business are hydrophilic and stable in alkaline pH, making them suitable for biological samples and aqueous applications.

Cytiva Whatman&trade Type WCN Cellulose Nitrate Membranes

Recommended for majority of routine applications, this membrane is manufactured under strictly controlled conditions. Whatman&trade Type WCN Cellulose Nitrate Membranes narrow pore size distribution for improved surface capture and analysis.

Sartorius Cellulose Acetate Membrane Filters

Combines high flow rates and thermal stability with very low adsorption characteristics. Sartorius Cellulose Acetate Membrane Filters are excellently suited for use in pressure filtration devices. Non-sterile filters in a variety of diameters and pore sizes are bulk-packed to save money and space.

Sartorius Microsart&trade e.motion Membrane Filters

Membrane Filters suitable for use in the Microsart e.motion dispenser

MilliporeSigma&trade S-Pak&trade Sterile Membrane Filter Kit

Made from mixed esters of cellulose and have been optimized for MF method microbiological analysis of water or other liquids

Cytiva Whatman&trade Cellulose Acetate Membranes

Prepares liquid scintillation cocktail for scintillation counter measurements. Whatman&trade Cellulose Acetate Membranes are highly heat resistant and can filter hot liquids and hot gases.

MilliporeSigma&trade Isopore&trade Polycarbonate Membrane Filters

Use for analyses of airborne contaminants and other particles using optical or electron microscopy. Isopore&trade Polycarbonate Membrane Filters have a smooth, glass-like surface for clearer sample observation. Available in a variety of pore sizes/flow rates, diameters and colors.

Types of Filtration

There are many different ways to filter matter, and below are just a few that we can use in the separating of substances.

Vacuum Filtration

In vacuum filtration, a vacuum pump is used to rapidly draw the fluid through a filter. Hirsch funnels and Buchner funnels, which are the same kind of funnel in two different sizes, are used along with filter paper. The funnels have a plate with holes in it, as we can see below, and they are usually used when the substance to be filtered is small in volume.

Centrifugal Filtration

This kind of filtration is done by rotating the substance to be filtered at very high speed. Due to the horizontal rotation, the more dense matter is separated from the less dense matter.

Gravity Filtration

This is where the mixture is poured from a higher point to a lower one. It is commonly done through simple filtration, using filter paper in a glass funnel, where the insoluble solid particles are captured by the filter paper and the liquid goes right through by gravity’s pull. Depending on the volume of the substance at hand, filter cones, fluted filters, or filtering pipets can be used.

Cold Filtration

This is often used for crystalline compounds that contain impurities. The way this filtration is done is by melting down the crystalline compound, removing the impurities as the substance is still in liquid form, and finally recrystallizing the now pure substance. Often, it is recommended that the apparatus used in this filtration be heated up so that the filtered substance doesn’t crystallize in the funnel and block the flow.

Multilayer Filtration

This can refer to multiple layers of different material, including sand, gravel, or charcoal, where the different layers contain different particle sizes of that material. In this type of filtration, a mixture of liquid and insoluble solid particles is poured over the layers, and the solid particles are caught throughout, resulting in a filtered liquid.

Membrane Applications

4.10.1 Introduction

Membrane filtration techniques have been used in the agro-food and bulk biotech industries for a long time, but the success story of today’s membrane processes in these industries did not start until Sidney and Sourirajan invented the phase inversion membrane in the 1960s. 1 This invention changed the membrane market and since then the total markets excluding medical applications have developed to a combined size of 12–14 billion Euro worldwide and are still growing strongly with an average annual growth rate (AAGR) of 8%–9%. Even though the largest membrane market is related to water and wastewater treatment including desalination, the membrane markets for the agro-food and bulk biotech industries (excluding pharmaceutical industry) are both significant membrane markets with worldwide volumes of 1.200–1.000 and 300–370 million Euros, respectively. The key membrane technologies in the agro-food and bulk biotech markets are microfiltration (MF) and ultrafiltration (UF) both with a market share of 30%–35% each, and nanofiltration (NF) and reverse osmosis (RO) with a combined market share of 25%–30%. Other membrane technologies such as membrane contactors (MC), electrodialysis (ED), pervaporation (PV), and vapor permeation (VP) have a small but increasing market share of less than 5%. The success of membrane technology in the agro-food and bulk biotech markets can be directly linked to some of the key advantages of membrane processes over conventional separation technologies:

Operation at low to moderate temperature ensuring a gentle product treatment.

Use of unique and highly selective separation mechanisms, such as sieving, solution-diffusion, or ion exchange mechanism.

Easy installation and extension due to modular design.

Reduced energy consumption in comparison with evaporators and condensers.

One of the challenging aspects in utilizing membrane processes in the agro-food and bulk biotech industries is the control of membrane fouling. Depending on the application, membranes tend to foul less or more severely. Fouling is commonly observed as a reduction of plant capacity over time. A common approach to reduce fouling and thus its impact on the membranes are regular cleaning intervals. In the agro-food and bulk biotech industries a cleaning interval of 24-h or after completion of a batch are common. The cleaning intervals can be integrated in the operation of the plant, for example, continuous back-flushing during operation or cleaning before plant shut-down—or/and integrated in the plant design, for example, having parts of the plant in production mode while other parts are in cleaning mode. If cleaning agents are required, caustic or acid cleaning agents are typically sufficient but also, for example, enzymatic cleaning agents are applied. Further, optimized plant operation can reduce fouling and thus the need for cleaning. Operation below the critical flux—the flux under which no fouling occurs—is an approach to maximize the time intervals between cleanings. However, this approach is commonly related with low flux/low pressure operation which, in reverse, has a negative impact on the plant size and thus investment costs. Alternatively, operation in the turbulent flow regime minimizes the effect of concentration polarization and thus reduces fouling. This approach on the other hand is related to higher operation costs since it increases the pressure drop along the module compared to laminar operation. Fouling can also be related to blockage of the module channels by feed material, for example, suspended solids such as fibers. The impact of this can be reduced by correct module selection, that is, open-channel tubular or plate-and-frame modules in case of presence of fibers. Further, pretreatment of the feed can help to optimize the plant performance by reducing/adjusting the level of suspended solids. Additionally, pretreatment can be an efficient way to control precipitation in the plant.

The first section of this article provides a brief overview of the main membrane processes used in the agro-food and bulk biotech industries. The following parts are on successful applications of membrane technology in these industries. The final section of this article will give a brief outlook on future developments in membrane technology within both agro-food and bulk biotech industries. It should be noted that each of the sections in the article is self-contained and therefore can be read independently of the others. The reader is therefore encouraged to move directly to sections of interest.

The nature and biology of basement membranes

Basement membranes are delicate, nanoscale and pliable sheets of extracellular matrices that often act as linings or partitions in organisms. Previously considered as passive scaffolds segregating polarized cells, such as epithelial or endothelial cells, from the underlying mesenchyme, basement membranes have now reached the center stage of biology. They play a multitude of roles from blood filtration to muscle homeostasis, from storing growth factors and cytokines to controlling angiogenesis and tumor growth, from maintaining skin integrity and neuromuscular structure to affecting adipogenesis and fibrosis. Here, we will address developmental, structural and biochemical aspects of basement membranes and discuss some of the pathogenetic mechanisms causing diseases linked to abnormal basement membranes.

Keywords: Collagen Discoidin domain receptor Heparan sulfate proteoglycan Integrin Laminin.

Copyright © 2017 Elsevier B.V. All rights reserved.


Core Basement Membrane Components and…

Core Basement Membrane Components and Binding Interactions. Laminins (Lms) are central organizers of…

Cell Membrane and Transport: Learn how transporters keep cells healthy

This is the full-length “Cell Membrane and Transport” simulation. For shorter, more targeted versions, see the Related simulations below.

Join Dr. B.I.O. Hacker in her synthetic biology lab, where she wants to change the world! In this simulation, you will learn about the structure and function of the cell membrane, and discover why membrane transporters are vital for healthy cells and the function of organ systems.

The synthetic biology lab

Your mission begins in the synthetic biology lab. Here you will meet Dr. Hacker, who will introduce you to the concept of selective permeability and the fluid mosaic models of the plasma membrane. Together, you will explore why cells need specialized transporter proteins to transport cargo molecules across their membranes.

Transport molecules into a virtual cell

Next, you will teleport to a virtual cell, where you will explore how different types of molecules can cross the cell membrane. While some molecules are able to diffuse across the cell membrane, most molecules require a transporter protein to enter or leave the cell. Explore the different channels, carriers, and pumps that exist in the membrane and how they ensure that only the right molecules enter under the right conditions.

Apply your knowledge

Return to the lab to test whether inserting a transporter protein in the membrane would help certain molecules to enter the cell. To do so, you will set up a fluorescence microscopy experiment to measure transport in living cells. Finally, discover how some transporter proteins do not only keep the cell healthy but also help organ systems to function. From filtration in the kidneys to the contraction of muscles during exercise, membrane transport contributes to many processes. Can you find out how?

Watch the video: IYPT 2020- 08. Soap Membrane Filter Report (January 2023).