chapter 7

with different pore sizes 02 or 04 m remove bacteria

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Unformatted text preview: t kill bacteria Physical Methods­ Filtration Physical Methods­ Filtration Exclusion of organisms through a particular pore size (viruses may still pass through pores) Used for air, and heat sensitive liquids Types: Depth filters: particulate material (porcelain, glass, earth, asbestos) Membrane filters: cellulose acetate, polycarbonate, etc.) with different pore sizes (0.2 or 0.4 µm) remove bacteria, let liquid pass through HEPA (high­efficiency particulate air) filters: used for hospitals, laminar flow hoods in laboratories, being marketed for home use to reduce allergens Membrane Filtration Membrane Filtration Chemical Methods Chemical Methods Affect proteins, cytoplasmic membranes or even DNA Can have a broad range of effectiveness depending on active chemical group Drawback: most agents have some toxicity to humans or environment The risk of harm needs to be weighed against the potential benefit Chemical Methods Chemical Methods 1. Alcohols: i.e. ethyl or isopropyl alcohol Coagulates proteins, damages lipid membranes Kills growing bacteria and fungi Limitation: alcohols evaporate q...
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