70% ethanol is used for sterilization and washing of sample in plant tissue culture, why not more or less than 70%?
Here (link below) has some explanation:
Pure Ethanol Prevents Cell Death
Testing has been done to show that when pure ethanol (at 100%) is poured onto a single celled organism, it will coagulate (clot) its protein. The ethanol penetrates its cellular wall in all directions. The protein located just within the cell wall is what coagulates. It’s much like a defense mechanism. This ring of coagulated protein actually prevents the ethanol from penetrating deeper into the cell wall of the organism. No more coagulation takes place. Basically, this renders the organism dormant, but doesn’t kill it. If the ethanol were to be washed away, then it’s possible the organism would come back to life.
This process defeats the purpose of using ethanol to kill microbes. Instead, scientists have found a way to trick these microbes with a lower percentage of ethanol.
How 70% Ethanol Causes Cell Death
In the same study, when the 70% ethanol was poured onto a single celled organism, the ethanol also caused its protein to coagulate, but this occurred at a much slower rate. This actually allowed the ethanol to penetrate the entire cell before it had a chance for its coagulation to block it. The entire cell is then coagulated, causing the cell to die.
https://www.compliancenaturally.com/blog-page/2018/4/15/why-70-ethanol-is-the-most-effective-disinfectant-for-any-food-or-pharma-facility
Hi Fatima, you're not the first person to ask this. Check out this research gate question from 2012 and the many responses for an answer to your question.
https://www.researchgate.net/post/Why_is_70_ethanol_used_for_wiping_microbiological_working_areas
Here (link below) has some explanation:
Pure Ethanol Prevents Cell Death
Testing has been done to show that when pure ethanol (at 100%) is poured onto a single celled organism, it will coagulate (clot) its protein. The ethanol penetrates its cellular wall in all directions. The protein located just within the cell wall is what coagulates. It’s much like a defense mechanism. This ring of coagulated protein actually prevents the ethanol from penetrating deeper into the cell wall of the organism. No more coagulation takes place. Basically, this renders the organism dormant, but doesn’t kill it. If the ethanol were to be washed away, then it’s possible the organism would come back to life.
This process defeats the purpose of using ethanol to kill microbes. Instead, scientists have found a way to trick these microbes with a lower percentage of ethanol.
How 70% Ethanol Causes Cell Death
In the same study, when the 70% ethanol was poured onto a single celled organism, the ethanol also caused its protein to coagulate, but this occurred at a much slower rate. This actually allowed the ethanol to penetrate the entire cell before it had a chance for its coagulation to block it. The entire cell is then coagulated, causing the cell to die.
https://www.compliancenaturally.com/blog-page/2018/4/15/why-70-ethanol-is-the-most-effective-disinfectant-for-any-food-or-pharma-facility
Thank you all! the point I got is : 100% ethanol completely coagulate the outer cells proteins and it works as defense mechanism in the cells of organism but in case of 70% ethanol, the ethanol does not completely coagulates the proteins of the cell hence penetrates in the organisms body and it dies. So the area becomes contamination free.
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