5.3
微生物生长控制的物理方法：辐射与过滤
辐射和过滤是控制微生物的重要手段，通过不同机制作用于微生物。辐射通过破坏微生物的DNA来消灭它们，既能杀死微生物，也能抑制其生长。根据波长的不同，辐射分为非电离辐射和电离辐射两类。
非电离辐射，如紫外线辐射（200–400 nm），被DNA吸收后造成损伤，从而有效消毒表面、空气和水体，包括安全柜。然…
辐射可杀死或抑制微生物的生长。
安全柜使用非电离紫外线辐射，可损伤DNA并消毒表面、空气和水，但由于其穿透能力有限，无法对罐头食品等大体积物品进行消毒。
电离辐射（如X射线和γ射线）可深入穿透物质，能够破坏内生孢子，对抗生素、医院用品和食品进行灭菌。
冷等离子体作为物质的第四态，可发射紫外线，现已成为一种强大的抗菌剂，可用于医疗器械的灭菌和食品保鲜。
过滤可去除大多数微生物，常用于对热敏感的液体和气体进行灭菌。
由纤维素酯或塑料聚合物制成、孔径为 0.2 μm 的膜滤器可去除大多数微生物，并对培养基、疫苗和抗生素进行灭菌。
深度过滤器（例如在安全柜、手术室和烧伤病房中使用的HEPA过滤器）可在其多孔基质中截留99.97%的颗粒物，包括病毒。
同样，N95 口罩可阻隔 95% 大于 0.3 μm 的空气传播颗粒物。
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Q1: How does UV radiation kill microorganisms in safety cabinets?
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.
Q2: What is the difference between ionizing and non-ionizing radiation for microbial control?
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.
Q3: Why is filtration preferred for sterilizing heat-sensitive liquids and antibiotics?
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.
Q4: How do HEPA filters and N95 masks protect against airborne microbes?
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.
Q5: What is cold plasma and how does it sterilize medical devices?
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.
Q6: Why can't UV radiation sterilize canned foods while gamma rays can?
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.
Q7: What pore size do membrane filters use to remove most microorganisms?
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.