Bio-transformations of natural and synthetic compounds are performed by using a large range of bacteria and fungi.
Can I use a magnetic stirrer for water insoluble compounds; or should I use emulsifying agents for this purpose?
I used to have the same problem with hydrocarbons like decane, so I used to start a culture in a liquid medium. Then I would add contaminations I was about to check. Next, I used to start cultures with a YPD medium, using cultures I started first using a liquid medium, as a source of inoculation. This allowed me to check, whether that particular yeast species would grow with such a source of carbon.
As for the cultures in a liquid medium, I'd leave the flasks on a rotary shaker and also every single day for some time I would take a sample of a culture in a liquid medium, in order to perform gas chromatography in the end. That test made it possible to find out, whether the cells used tested contamination as a source of carbon.
You can keep the compound in liquid cultures in a rotary shaking incubator with desired temperature and rpm. If the solubility of the compound is too low and the reaction is slow due to low availability, you can try adding some emulsifying agents, biological surfactants can be a choice.
Hi Ammar
Biggest difficulties are, that you have a very low surface / diffusion also the total oxygen transfer is reduced for low boiling chemicals, thry can build a steam layer , heavier than air, and, as you do not blow air actively inside. If the surface is dramatically too low, your reaction will not run or with very poor conversion
You can use submer Polystyrene Carriers beads like the XADs to increase the surface and enhance the oxygen transfer, for non-vaporating chemicals, you can use an emulsifier, the Tweens f.E. are most widely accepted from many MOs
For palting on agar, saturation of the atmosphere, inside a box f.E, is suitable for low boiling substances, stable emulsification for non-vaporating substances on the plates for non-evaporating components during the production of the plates is possible
I have worked with bioconversion of Progesterone to 11-alpha-hydroxyprogesterone using fungal strains. I used a low concentration of solvent that was tolerated by fungal strains to improve substrate solubility and used a magnetic stirrer to keep the substrate dispersed (I used a 5 Lt Schott bottle as a mini bioreactor in absence of actual bioreactor). Using micronized substrate powder also helped. If you are using a small bioreactor, there should be no problem of keeping substrate dispersed. Uptake will definitely be an issue as others have already indicated, but dispersing or emulsifying agents can help. The challenges could be also in analytical measurements to obtain representative samples. Type of microbial strain you need to use for bioconversion will also be an important issue. I would prefer to use a small bioreactor than shake flasks, if you can avail the facility though. Give it a go, and I am sure you will work it out as I did.
Magnetic stirbars can destroy filamentous structures, no problem for the yeasts, but if you really want to screen on a whide spectra of different MOs it might be problematic.
If you do not emulsify propperly, you will stay with the same problems: low surface contact and possible airation problems
For better growth ofMOs forming filamnetous structures you can check anionic detergents like Carbopol 934, it is excellent to keep fungus shakeabele in flask culturs, because the spores keep widely separated an the growth is non-flilamentous, like a standard bacterial culture.
Usually fungi are forming filamentous structures on the surface of this cultures on the wall of flasks. As a deterget it should also help to immulsify lipidic components.
Dear Ammar
Even if fermentation is not my field of expertise, I know there is a research line on two-phase partitioning bioreactors (TPPBs) that has been used in extractive fermentation when you have product inhibition. We, in enviromental biotechnology, useTPPB to biodegrade poorly water soluble compounds and to enhance the gas-liquid mass transfer of hydrophobic gas pollutants.
Take a look into the reference of this paper. This might help you out
Muñoz R, Villaverde S, Guieysse B, Revah S. (2007). Two phase partitioning bioreactors for the treatment of volatile organic compounds. Biotechnology Advances. 25(4): 410-422.
Raul
Article Two partitioning bioreactors for treatment of volatile organ...
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