5.3
Physical Methods for Controlling Microbial Growth: Radiation and Filtration
Radiation kills or inhibits the growth of microorganisms.
Safety cabinets use non-ionizing UV radiation, which damages DNA and disinfects surfaces, air, and water, but its limited penetration prevents it from disinfecting bulk items like canned foods.
Ionizing radiation, such as X-rays and gamma rays, penetrates deeply, destroying endospores, sterilizing antibiotics, hospital supplies, and food.
Cold plasma, the fourth state of matter that emits UV rays, has emerged as a powerful antimicrobial agent used to sterilize medical devices and preserve food.
Filtration removes most microbes and is used to sterilize heat-sensitive liquids and gases.
Membrane filters with 0.2 μm pores, made of cellulose esters or plastic polymers, remove most microbes and sterilize culture media, vaccines, and antibiotics.
Depth filters, such as HEPA filters used in safety cabinets, operating rooms, and burn units, trap 99.97% of particles, including viruses, within their porous matrix.
Similarly, N95 masks block 95% of airborne particles above 0.3 μm.
Radiation and filtration are essential tools for microbial control, targeting microorganisms through distinct mechanisms. Radiation eliminates microbes by damaging their DNA, either killing them or inhibiting their growth. Based on wavelength, radiation is classified into two types: nonionizing and ionizing radiation.
Non-ionizing radiation, such as UV radiation (200–400 nm), is absorbed by DNA, causing defects that effectively disinfect surfaces, air, and water, including safety cabinets. However, its inability to penetrate thick layers renders it unsuitable for sterilizing bulk objects like canned foods. In contrast, ionizing radiation, including X-rays and gamma rays (wavelengths shorter than 1 nm), penetrates deeply into objects and destroys all microbes, including highly resistant endospores. This makes ionizing radiation invaluable for sterilizing vaccines, antibiotics, and hospital supplies, and eliminating pathogens from food products.
An emerging technique in microbial control is cold plasma, the fourth state of matter, which emits UV rays and exhibits remarkable antimicrobial properties. Cold plasma is increasingly used for sterilizing medical devices and preserving food, offering a versatile and effective solution.
Filtration, a chemical-free method, removes microorganisms and is ideal for sterilizing heat-sensitive liquids and gases. Two key filter types are membrane filters and depth filters. Membrane filters, made from cellulose esters or plastic polymers, have pore sizes as small as 0.2 μm, effectively removing most microbes. These filters are widely used for sterilizing culture media, vaccines, and antibiotics.
Depth filters, such as HEPA filters, trap 99.97% of particles, including viruses, within their porous matrix. Their granular structure adsorbs particles, making them critical for sterile environments in safety cabinets, operating rooms, and burn units. Similarly, N95 masks, designed to block 95% of airborne particles larger than 0.3 μm, provide essential personal protection against microbial threats.
Together, radiation and filtration are indispensable for ensuring microbial safety in healthcare, research, and daily life.
Radiation kills or inhibits the growth of microorganisms.
Safety cabinets use non-ionizing UV radiation, which damages DNA and disinfects surfaces, air, and water, but its limited penetration prevents it from disinfecting bulk items like canned foods.
Ionizing radiation, such as X-rays and gamma rays, penetrates deeply, destroying endospores, sterilizing antibiotics, hospital supplies, and food.
Cold plasma, the fourth state of matter that emits UV rays, has emerged as a powerful antimicrobial agent used to sterilize medical devices and preserve food.
Filtration removes most microbes and is used to sterilize heat-sensitive liquids and gases.
Membrane filters with 0.2 μm pores, made of cellulose esters or plastic polymers, remove most microbes and sterilize culture media, vaccines, and antibiotics.
Depth filters, such as HEPA filters used in safety cabinets, operating rooms, and burn units, trap 99.97% of particles, including viruses, within their porous matrix.
Similarly, N95 masks block 95% of airborne particles above 0.3 μm.
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5.3 : Physical Methods for Controlling Microbial Growth: Radiation and Filtration
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