I have run Mucor and Mortierella filamentous fungal fermentations in 42L total volume, in situ sterilizable pilot bioreactor, with 25L initial volume. Stirrer speed was moderate (300-450 rpm) during cultivation. I observed excessive wall growth (on the wall, baffles, stirrer) that accounted for around 40% of total biomass. Is there any method to prevent such behaviour? Thank you in advance.
Increasing the orbital speed in the incubator (or any shear force such as air bubbles i.e.) could do it, because it would break the filaments. However, it will also cause a stress and you may hider fugal growth. It depends on the species.
I don't know what are you producing and whether the stirring speed you mentioned is optimum for your maximum production, because sometimes excessive biomass is not an indication of optimum production. If however, increasing agitation prevents wall growth without compromising the production parameter or whatsoever in your case, you can give a try or as suggested by Sir Jai Ghosh shake culture could prove better for you if your set up favours it as it seldom allows the mycelium to get grip on wall surface but at the same it shouldn't hamper the active production rate or amount.
Dear Harmen, the product is single cell oil, which is intracellular, therefore high biomass yield is preferred. Shaken culture is not really feasible at 25L scale. I kept DO at 20% of saturation with varying stirrer speed and 0.5VVM. I know that Mortierella alpina is shear stress sensitive, so increasing stirrer speed might not be a good solution in this case. The biomass yield was not high, around 15 g/L, but as I mentioned around 40% of this ("excessive amount") was grown on the wall of the fermenter instead of in the broth.
For glass surface of fermentors there is method of chemical treatment which prevent them from the wall growth during fermentation processes.
Interesting. What is this treatment? Is there similar approach for stainless steel as well?
It is a treatment by 5% solution of dimetyldichlorsilan in isopropanol during 3 - 5 minutes and after that the vacuum drying under temperature 100 - 110 oC. Sorry for my bad English. I can send you an article only in Russian.
HI,
MAY BE THE STRAIN CAN BE MANIPULATE TO PELLET STRAIN... U CAN AVOID SUCH PHENOMENON.....EARLIER PAN LABS ARE DOING THIS ...
Dear Dr. Biryukov, Thank you for your answer. Please send me the Russian article to [email protected]. Thank you in advance.
Dear Dr. Kosa,
For stainless steel passivation, I suggest to use nitric acid with high precaution.
Regards.
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