Question 1

How does UV radiation kill microorganisms in safety cabinets?

Accepted Answer

UV radiation, a non-ionizing radiation type, is absorbed by microbial DNA, causing defects that kill or inhibit microorganisms. Safety cabinets use UV radiation to disinfect surfaces, air, and water effectively. However, UV radiation has limited penetration depth, making it unsuitable for sterilizing bulk items like canned foods.

Question 2

What is the difference between ionizing and non-ionizing radiation for microbial control?

Accepted Answer

Non-ionizing UV radiation damages DNA but cannot penetrate thick layers, limiting its use to surfaces and air. Ionizing radiation, such as X-rays and gamma rays, penetrates deeply and destroys all microbes, including highly resistant endospores. This makes ionizing radiation ideal for sterilizing vaccines, antibiotics, hospital supplies, and food products.

Question 3

Why is filtration preferred for sterilizing heat-sensitive liquids and antibiotics?

Accepted Answer

Filtration is a chemical-free method that removes microorganisms without applying heat or chemicals, making it ideal for heat-sensitive materials. Membrane filters with 0.2 μm pores, made of cellulose esters or plastic polymers, effectively remove most microbes from culture media, vaccines, and antibiotics while preserving their integrity.

Question 4

How do HEPA filters and N95 masks protect against airborne microbes?

Accepted Answer

HEPA filters trap 99.97% of particles, including viruses, within their porous matrix through adsorption, making them critical for sterile environments in operating rooms and burn units. N95 masks block 95% of airborne particles larger than 0.3 μm, providing essential personal protection against microbial threats in healthcare and daily settings.

Question 5

What is cold plasma and how does it sterilize medical devices?

Accepted Answer

Cold plasma is the fourth state of matter that emits UV rays and exhibits remarkable antimicrobial properties. It is increasingly used for sterilizing medical devices and preserving food, offering a versatile and effective solution for microbial control that complements traditional radiation and filtration methods.

Question 6

Why can't UV radiation sterilize canned foods while gamma rays can?

Accepted Answer

UV radiation has limited penetration depth and cannot pass through thick layers or opaque materials like metal cans. Gamma rays, an ionizing radiation type with wavelengths shorter than 1 nm, penetrate deeply into objects and destroy all microbes, including endospores, making them effective for sterilizing packaged food products.

Question 7

What pore size do membrane filters use to remove most microorganisms?

Accepted Answer

Membrane filters use pore sizes as small as 0.2 μm to effectively remove most microorganisms from liquids and gases. These filters, made from cellulose esters or plastic polymers, are widely used for sterilizing culture media, vaccines, and antibiotics, providing reliable microbial removal without damaging heat-sensitive materials.

שיטות פיזיקליות לשליטה בצמיחה מיקרוביאלית: קרינה וסינון

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