I'm growing a yeast-like fungus in a culture medium. After several days, I remove cells via filtration and get supernatant. Then I need to sterilize the supernatant to make sure it is bio-safe so that i can use it to do animal treatment.
However, sterilizing at high temperature would kill the active substance inside the supernatant, such as denaturing an enzyme. Also, there could be other molecules inside that is temperature sensitive.
Is there any way to safely "sterilize" a supernatant without destroying its activity?
Thanks a lot!
Hi there,
Filtration on 0.22 µm does it. As an alternative UV or gamma irradiation should be considered.
I also would like to suggest the use of the ionizing radiation technique for sterilization purpose using gamma radiation, or other equivalent irradiation equipment.
If you are planning to treat animals with the filtrate, you should test it for endotoxin.
Hi Suipwksiow
Read some reference 1
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4041171/
2
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC550959/pdf/iai00173-0167.pdf
As people mentioned, the standard method to do this is filtration, especially vacuum filtration. Just make sure you are using at least a 0.22 micron filter as some papers talk about "sterilization" using a 0.45 micron filter. As the World Health Organization states, "membranes of not greater than 0.22 μm nominal pore size should be used. The effectiveness of the filtration method must be validated (e.g. https://www.ncbi.nlm.nih.gov/pubmed/16570864) if larger pore sizes are employed". Note that filtration like this will not remove viruses, so if that is a possibility, some other form of sterilization, such as gamma irradiation, may be needed.
Clarification or pre-filtration with a 0.45 micron filter or larger may speed up filtration through the sterilization filter, so these often are stacked or run as a series. You may have to test some different types of filters to as some types may bind certain compounds or have better flow for different types of fluids.
To sterilize a supernatant, the supernatant should be filtered through four layers of muslin cloth, centrifuged at 4000 rpm for ten minutes followed by filtration through sterilized Whatman filter paper No. 1. Please read the following article
Javaid A, Ali S (2011). Herbicidal activity of culture filtrates of Trichoderma spp. against two problematic weeds of wheat. Nat. Prod. Res., 25: 730-740.
Good look
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