MicroEco Midterms

• Principal Methods


  • Membrane-filtration method
  • Presence–absence tests
  • Multiple-tube method

  
• Membrane Filtration Technique


  1. Filtration

  2. Membrane filtration mechanism

  
• Membrane filter


  Also known as the molecular or biological filter

  
• Membrane Filtration Technique


  • Used in biology laboratories to sterilize liquids
  • Used to determine the quality of water and the quantity of microorganisms

  
• Purpose of Membrane filtration technique

  To ascertain the residence or absence of a particular coliform group that is usually existing in wastewater and groundwater

  
• Membrane filtration unit components


  • Water sample
  • Funnel
  • Locking ring
  • Forcep
  • Membrane Filter
  • Stainless base
  • Rubber stopper
  • Filter flask
  • Vacuum pump

  
• Advantages of Membrane Filtration Technique

  • Quicker: quantitative results in about 18 hours
  • Less labour-intensive
  • Requires less culture medium
  • Requires less glassware
  • Result obtained directly by colony count (high precision)
  • Readily adaptable for use in the field
  • No requirement for chemicals
  • Can remove 90–100% pathogens from the water sample

  
• Disadvantages of Membrane Filtration Technique

  • Not applicable to turbid waters
  • There may be a risk of bacterial abundance, as the water carries numerous microorganisms
  • Glass filters are breakable and can break quickly
  • The membrane filters can crack easily
  • Only liquids are sterilized by this method
  • Filters are costly to repair, mainly nano-filters
  • Constitutional restrictions of supplies used in filters alter the effectiveness of this process such as damage of glass filters, fracture of the membrane filter, and consumption of the filtrate by Sietz filter
  • Require a high differential pressure
  • Clogging can occur

  
• Applications of Membrane Filtration Technique

  • In industries and laboratories, it is used to sterilize the heat-labile fluid materials
  • Most effective and acceptable method for filtration of drinking water
  • In the pharmaceutical, cosmetics, electronics, and food and beverage industries is is used to monitor the bacterial cells
  • Used in wastewater treatment
  • Used in cold sterilization of beverages and pharmaceuticals
  • Used for separation of milk fraction
  • Used to concentrating the proteins
  • Used for defeating skimmed milk and whey
  • Used for the partial demineralization of whey

  
• Types of membrane filtration

  • Microfiltration
  • Ultrafiltration
  • Nanofiltration
  • Reverse osmosis (RO)

  
• Microfiltration


  Separates particles in the size range of 0.1 to 10 μm, used to separate pathogens like Cryptosporidium and Giardia lamblia
• Ultrafiltration


  Membrane pore size ranges from 0.1 μm to 0.01 μm, used for production of potable water by removing particulates and macromolecules

  
• Nanofiltration


  Membrane pore size ranges from 0.001 μm to 0.01 μm, used in fine chemistry and pharmaceuticals for solvent recovery and management
• Reverse osmosis (RO)


  Membrane pore size ranges from 0.0001 μm to 0.001 μm, used to purify rainwater collected from storm drains

  
• Multiple-tube method


  Statistical estimation of total coliform density in environmental water sources
• The coliform group analyzed in the multiple-tube method is defined as all aerobic and facultative anaerobic, gram-negative, non-spore-forming, rod-shaped bacteria that ferment lactose with gas formation within 48 hr at 35C
• Materials used in Multiple-tube method

  • Flask
  • MacConkey broth
  • distilled water
  • Autoclave
  • Durham tube
  • Brilliant green lactose bile broth (BGLB)
  • Eosin methylene blue agar medium (EMB)
  • EMB medium
• Advantages of Multiple-tube method

  • Applicable to all types of water
  • May give better recovery of stressed or damaged organisms under some circumstances
• Disadvantages of Multiple-tube method

  • Slower: requires 48 houirs for a negative or presumptive positive result
  • More labour-intensive
  • Requires more culture medium
  • Requires more glassware
  • More sensitive
  • Result obtain indirectly by statistical approximation (low precision)
  • Not readily adaptable for use in the field
• Presence–absence tests


  Presumptive detection for coliforms in water based on the principle that coliforms and other pollution indicator organisms should not be present in a 100 mL water sample
• Materials used in Presence–absence tests

  • 20ml glass sampling bottle
  • alcohol
  • HACH PathoScreen Medium for 20ml
  • 100ml glass bottle
  • candle, lighter, alcohol
  • UV lamp
  • HACH Lauryl Typtose with Bromcresol Purple (LT/BCP) Broth with MUG reagent for 100ml sample
• Advantages of Presence–absence tests

  • No special skills are required (anyone who can recognize the species can do the monitoring) and that the monitoring requires very little time
  • Presence/absence sampling can be a very fast method for collecting information if the only thing that is needed is knowledge of whether or not something was present
  • Can perform well for measuring or understanding the distribution of things across landscapes
• Disadvantages of Presence–absence tests

  • A significant limitation of this method, however, is that it does not provide information on things like the abundance, density, or condition of individuals at the site. These factors can be important leading indicators of changes that might take a long time to be expressed through changes in distribution
• Indicator organisms


  Microorganisms used to detect the presence of other microorganisms, especially pathogens, in water
• Principal methods for isolating indicator organisms from water

  1. Membrane-filtration method

  2. Presence–absence tests

  3. Multiple-tube method

  
• Membrane-filtration method


  • Effective for sterilizing heat-sensitive materials
  • Used to sterilize various liquids and gases, including air
  • Acts as a barrier, removing contaminating microorganisms rather than destroying them
  • Comprises millions of pores that permit the passage of liquid or gas
  • The pores are smaller than microorganisms, trapping particles larger than the pores

  
• Types of filters used in membrane filtration

  • Asbestos pad (Seitz filter)
  • Diatomaceous earth (Berkefeld filter)
  • Porcelain (Chamberland-Pasteur filter)
  • Sintered glass disks (Sintered glass filter)
  • Cellulose (Membrane filter)
  • Borosilicate glass fiber (HEPA filter)
  • Mud (Candle filter)

  
• Membrane filtration technique


  • Also known as the molecular or biological filter
  • Widely used in biology laboratories to sterilize liquids
  • Used to determine the quality of water and the quantity of microorganisms

  
• Membrane filtration mechanism

  A part of fluid termed a permeate (filtrate) moves within the membrane, while other components are expelled by the membrane and clutched in the retentate (concentrate) steam

  
• Membrane filtration unit/assembly


  • Advantages: quicker, less labour-intensive, requires less culture medium and glassware, less sensitive, high precision, readily adaptable for field use, no requirement for chemicals, can remove 90–100% pathogens
  • Disadvantages: not applicable to turbid waters, risk of bacterial abundance, breakable glass filters, membrane filters can crack easily, only liquids are sterilized, costly to repair, require high differential pressure, clogging can occur

  
• Applications of membrane filtration

  • Sterilizing heat-labile fluid materials in industries and laboratories
  • Filtration of drinking water
  • Monitoring bacterial cells in industries like pharmaceutical, cosmetics, electronics, food and beverage
  • Wastewater treatment
  • Cold sterilization of beverages and pharmaceuticals
  • Separation of milk fractions
  • Concentrating proteins
  • Defeating skimmed milk and whey
  • Partial demineralization of whey

  
• Types of membrane filtration

  • Microfiltration
  • Ultrafiltration
  • Nanofiltration
  • Reverse osmosis (RO)

  
• Microfiltration


  Separates particles in the size range of 0.1 to 10 μm, used to remove pathogens like Cryptosporidium and Giardia lamblia

  
• Ultrafiltration


  Pore size ranges from 0.1 μm to 0.01 μm, used for production of potable water by removing particulates and macromolecules

  
• Nanofiltration


  Pore size ranges from 0.001 μm to 0.01 μm, used in fine chemistry and pharmaceuticals for recovery and management of non-thermal solvents and room temperature solvent exchange
• Reverse osmosis (RO)


  Pore size ranges from 0.0001 μm to 0.001 μm, has the finest separation membrane, used to purify rainwater collected from storm drains

  
• Multiple-tube method


  1. Statistical estimation of total coliform density in environmental water sources

  2. Coliform group defined as all aerobic and facultative anaerobic, gram-negative, non-spore-forming, rod-shaped bacteria that ferment lactose with gas formation within 48 hr at 35C

  
• Materials used in multiple-tube method

  • Flask
  • MacConkey broth
  • Distilled water
  • Autoclave
  • Durham tube
  • Brilliant green lactose bile broth (BGLB)
  • Eosin methylene blue agar medium (EMB)
  • EMB medium
• Presumptive test in multiple-tube method

  1. Determines if there are coliform bacteria present in the water sample

  2. Coliform bacteria ferment lactose sugar in a lactose broth medium, producing gas bubbles

  
• Confirmatory test in multiple-tube method

  1. Verifies the results of the presumptive test

  2. Uses BGLB broth and EMB agar to distinguish between coliform bacteria and other types of bacteria