Membrane Filter Technique | Membrane Filtration Method
Microbes are considered as an important microorganisms, its have different types, sizes and uses, Bacteria for example can be found everywhere; it has sizes from 0.2 µm to around 3 µm. Coliform bacteria testing known as the most microbes detected for water, and the presence of Escherichia coli (size: 1 µm) is an indication for the presence of pathogens that leads to water contamination. Membrane Filtration Technique is the popular method for the detection of many microbes, it can detect up to 300 Colony Forming Unit (CFU), and it has the ability to detect different types according to media and sample types.
Membrane Filtration need the following equipment in general for work:
Laminar Flow Hood (Optional).Vacuum Pump with Rubber Tube.
Suction Flask 1 L.
Nitrocellulose Filter, Pore Size: 0.45 µm.
Microbiology Media.
Sterile Distilled Water.
70% Ethanol.
Flame.
Forceps.
Incubator.
Autoclave.
Tissue Paper.
Sterile cups or Sterile bags.
Suction Funnel.
Sample Collection:
Sample types and collection methods are different, Samples may be water, beverage, swab, sugar, or syrup. In this article an explanation of water sample will done. Water samples are collected from tanks as follow:
Wet piece of tissue paper by 70% ethanol and wipe the valve of the tank.Open the valve to let some water out to erase any excess of ethanol then close it.
Open the sterile bag or sterile cup in the same time open the valve and take 100 ml then close the valve and the bag / cup.
Transfer the sample to Microbiology lab immediately.
Water Samples can be stored in refrigerator at 4°C to inhibit the growth and the rise in microbial numbers.
Working Procedures:
Turn on UV lamp and take time according to laminar hood type.
Turn on air flow (that will turn off UV lamp), then clean all the tools again by 70% ethanol.
Enter water sample inside the hood and clean it by 70% ethanol.
Put the filter on the suction funnel and pour half of the sample then turn on the pump and pour the other half.
Turn off the pump when all sample content filtered.
Mount the filter on media plate and incubate it on the proper temperature inside the incubator.
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