I was at a gathering and someone suggested that a lady could rinse a cup with some alcohol because it can “kill germs” and somehow, I became annoyed. So I used that opportunity to school him a little on microorganisms 😉.
I’m here to teach you too 😅
I remember when I learnt that 100% alcohol cannot kill microorganisms, but 70% can. This didn’t make sense to me. I’m like, how is that possible? 😅
In the laboratory, we use 70% alcohol (especially ethanol) to sterilize work benches, our hands, laboratory bottles, and some equipments.
A lot of hand sanitizers also contain some alcohol.
Scientists have established that 50-80% alcohol is optimal for killing microorganisms.
- 100% alcohol evaporateS fast, and may not have time to penetrate the cell wall of bacteria 🦠
- 100% alcohol, can inactivate bacteria, but not kill it. So, the organism may continue to function under favorable conditions.
This might give you an idea as to why 50-80% can do the work.
But I’ll tell you anyway,
Dilute alcohol will move into the bacterial cell wall slower due to the high osmotic pressure of the ethanol/water mix.
This mix will denature the proteins and destroy the cell wall as they slowly permeate into the cell, thereby inhibiting growth.
So any alcohol-water mixture less than 50% might be too dilute and may not even do anything. Anything above 80% might be too concentrated and can evaporate quickly.
I hope you learnt something new today!
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