MCB 2610 Chapter Notes - Chapter 6B: Louis Pasteur, French Wine, Pasteurization
8 Sep 2016
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When microorganisms die, they do not die all at once or instantaneously: they die logarithmically/exponentially. Measure of agent"s killing efficiency: decimal reduction time (d-value) time to kill 90% of microorganisms and spores in a sample under specific conditions. Allows you to compare all organisms on the same scale: z-value temperature change needed to kill 90% of microorganisms and spores in a sample under specific conditions. Must be sure persister cells (viable but not culturable; vbnc) are dead. Once they recover they may regain ability to reproduce and cause infections. Standardized: viruses can be removed from liquids by ultrafiltration methods (reducing pore size 10 to 100 nm, problems with filters. Large particles clog: ultrafiltration requires high pressure, viscous liquids don"t filter well, membrane filters. Porous membranes with defined pore sizes that remove microorganisms primarily by physical screening. Have replaced depth filters for the most part. Culture media: e. faecalis is too large to be filtered.
