Its difficult to determine the aeration rate in flasks, however, you can easily set the aeration rate, depending upon the metabolism of your culture..!!

This is on of the most basic topics when dealing with aerobic bioprocesses. In order to mimic the aeration (or better said oxygen transfer) in a fermenter and a shake flask, one simply must determine the volumetric oxygen mass transfer coefficient kLa in the flasks and provide the same value in the fermenter. Such measurements are easy and can be routinely performed. By matching the kLa's values you will provide similar aeration conditions in both cases. There are a number of different methods to measure kLa (just consult a basic bioprocess engineering handbook) - you may choose the most adequate for your case depending on the analytical equipment and chemicals you have available. There are might be some other changes in the cultivation conditions because of the scale-up (passing from a flask to a fermenter (even if the KLa is maintained the same), for example due to sensitivity to your culture to mechanical stress. As the very name says, aeration in a flask is due to "shaking" while in a bigger fermenter is, not always, but most often provided by air bubbling + mechanical agitation. But this is already another story...

I appreciate ur help dr.svetlozar.. Thank u very much!

The aeration rate depends on the neck diameter of your flask and the type of plug (cotton, rubber, metal cap) you are using. For more information please contact the ShakingTechnology-Team at www.shakingtechnology.com . The calculation method we use is decribed in the following publication:

Mass transfer resistance of sterile plugs in shaking bioreactors.

Mrotzek C, Anderlei T, Henzler H, Büchs J.

Biochem Eng J. 2001 Mar;7(2):107-112

Found ur article britta anderlei. Thanks

Thanks mr.dhillon

In scale up, scale is usually changed while holding one parameter constant. In your case you are asking about moving from flask to bioreactor while keeping aeration the same. By keeping aeration the same I presume that you mean kLa. Svetlozar has given you a suggestion on how to measure that is flasks. However, I am sure that you realize that the same value of kLa in a flask and in a bioreactor is not achieved under identical conditions. For example, in a bioreactor impeller tip speed and impeller type makes a difference. Thus while the kLa values may be the same in a flask and a bioreactor, cultures in the latter may be suffering from more shear forces.

Clem

In addition to the other precious and correct answers there is some other point. Scaling up towards a lab scale bioreactor probably the accumulation of CO2 is not a big concern. The sufficient airation also eliminates the CO2. In my view the flask also gets rid of it due to the high driving force - concentration (I never measured). The big step is going further into industrial scale. The hydrostatic pressure helps (~Henry's law) keeping the dissolved gas concentration high. Nevertheless in case of CO2 too, not only in case of O2 (which is helpful in deed). The accumulated CO2 can throttle the physiological activity in spite of a good level of O2.

For scaling up in fermentor or bioreactor you should calculate volumetric oxygen mass transfer coefficient kLa from shaker flask (KLa) and use this KLa to the fermenter.

Dear Siswa Setyahadi,

You are completely right!

What I mentioned is a bit addition to it and works only in idustrial scale.

This means in a high fermenter where every one meter height gives cca. 0,1 Bar plus hydrostatic pressure at the bottom part of the equipment. Here besides the fulfilling the criterion of the necessary Kla, the high opartial pressure of the dissolved CO2 can have a negative impact. Therefore in some cases the airation should be higher than necessary just for fulfilling the O2 demand.

Dear alls

You have to consider both two things: oxygen concentration and flux (KlA) and also CO2 (concentration and flux) .Results on shake flasks have no ventilation, so CO2 concentration is higher than during the fermentation (and in fermentor ), mainly in the beginning .

One error is often to consider only the problem of oxygenation and only the problemation of aeration . It is necessary to watch the problem of ventilation effects via the true CO2 concentration.

This is one problem for transfering results from the flasks to the fermentors . G Goma

Well 'am not a biochemical engineer so can't comment much on all those different techniques everyone said above, which is actually necessary for any fermentation industry before starting any new product. But I can suggest few 'layman' things from my experience with fermentation for past 10 years. 'Working volume to total volume ratio' makes a big difference for aeration, like in your case you have used 100ml media in 500 ml flask (we are using same 50ml media in 250ml flask) but the volume in fermentor is 3L in 5L capacity. Even after deciding the Kla for your flasks and the vessel one can't exactly extapolate the scale-up conditions (as mentioned by Svetlozar and all). As in vessel you will have baffels (unless you are using baffeld flasks), aerator (type of sparger and the LPM air transfer) and the design of the agitator blades (and speed) will have major role to play. So, its always better to refer some reported standerdized conditions for the product OR use DOE for environmental parameters/ conditions for optimising the production. As in fermentor you have several criteria to play with and optimise the feremntation: run the vessel in cascading mode (with LPM and agitation speed), control/regulate backpressure (if your fermentation is not sensitive to CO2), etc.

Best Luck for Scale-up.

it depends on the growth rate of the cells used, for E.coli the flask and fermenter trials almost not comparable, for slow grow cells (0.1 h-1 or below) it might be comparable and for flask you should use the maximum agitation (typically) 300 rpm with medium/flask volume around 10 (it means you should use 1000mL flask for 100ml medium), and for this case your fermenter agitation should be in the same range of 250-300 rpm, tip - the flask trials are typically used for estimation or to find a trend of the parameter you test and the main results should be obtained from the fermenter trial where you can control pH/DO-levels that is not possible to do in the flask trial.

Perhaps of some interest for your query:

https://www.researchgate.net/post/How_can_KLa_be_calculated_in_a_flask