A microbiological Hua broth medium modified was intended to be used in yeast growth for biosurfactant production. Accordingly, it was important to measure its surface tension to assume if any alteration occurs proving that there is a microbial product affected its surface tension. At zero time of inoculation, the broth gave me 95 mN/m measured by capillary rise technique. The medium structure is (g L-1): KNO3 2.5, KCl 0.1, KH2PO4 3.0, K2HPO4 7.0, CaCl2 0.01, MgSO4.7H2O 0.5, yeast extract 1.0, supplemented with soybean oil (8%, v/v), at pH 7.0.
added to this question ..
Is it logical that surface tension of any prepared media containing salts and organic sources to exceed that of water (72mN/m)
If so .. how can we mathematically calculate possible surface tension based on mixed salt concentrations in a solution ?
The answer to your first question is YES: the surface tension of a cultivation medium can be 95 mN.m-1.
I am not sure that your though
" Is it logical that surface tension of any prepared media containing salts and organic sources to exceed that of water (72mN/m) " is correct. What about the situation when a cultivation medium contains some compound lowering the surface tension?
Best regards
Vit
I do not believe that is possible with this culture medium. Did you measure the surface tension of water using the same equipment? Furthermore, the presence of oils or hydrocarbons in the culture medium always results in a surface tension reduction.
This value is very strange. Only water has an unusually high surface tension because of the relatively high attraction of water molecules to each other through a web of hydrogen bonds, water has a higher surface tension than most other liquids - 72,7 mN/m. I propose measure just pure water by the same methodology. If you will be measure 72,7 mN/m, then your value for the medium is correct.
Dear Pavel Dostálek .. Surface tension was measured for water and 5 media used in this research [a file is attached] .. putting in consideration that many different salts increase surface tension of water in accordance to their type and concentrations, but as I have no experiences in physical chemistry and hydrodynamics, I can not establish a good explanation for those results.
Dear Vit Mateju .. and .. Eduardo J Gudiña .. It is true that oils lower the surface tension
but the surface tension was measured in media before adding oil as it is a variable nutrient that will be mostly consumed by the microorganism to produce the bio-surfactant
also surface tension of media after growth and production was measured after extracting the residual oil used
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