How to optimize bioreactor performance using mass controllers.

We are currently in a race against time in the development of new vaccines against infectious diseases. In the biopharmaceutical world, the efficiency and technological productivity of bioreactors is a key point in this development. Bioreactors create the optimal environmental conditions of temperature, nutrient concentration, pH, dissolved oxygen, … for fermentation and/or cell culture production. The higher the yield of the bioreactor cell culture, the higher the probability of obtaining a quality product: Vaccine, pharmaco….  

Bioreactor operation

There are two fundamental variables that directly influence the operation of a bioreactor, dissolved O2 and pH. Both are directly dependent on accurate and reliable control of the gas flow rate. The amount of O2 dissolved in the medium must be reduced or increased by precise injection of O2 or N2. Since O2 is relatively insoluble in water, the amount of air is usually added constantly to maintain an O2 concentration that favors bioreactor performance. The pH of the medium is usually regulated by the addition of acids and/or bases. In the case of cell cultures, liquid acids could damage the cells; instead, acidification is usually performed by addition of CO2 . For CO2 flow rate adjustment, bioreactor manufacturers have traditionally used rotameters with a manual valve. These systems have obvious limitations, so the current trend is to replace them with digital mass flow controllers.  

Advantages of mass controllers.

First, both rotameters and differential pressure controllers are volumetric systems. Therefore, small variations in Pressure (P) and Temperature (T) result in a significant error in the flow measurement. The mass instruments, unlike the previous ones, are totally independent of P and T, and do not require any compensation. On the other hand, it is evident that an automatic flow control is critical for a good functioning of the bioreactor. Despite the economic advantages of rotameters, they do not have any output signal that would allow them to automatically handle variations in the conditions required for optimal bioreactor operation. Other important aspects are the size of the mass controller, and its versatility. For example, the ability to handle different gases (O2 and N2) with the same equipment is always an interesting feature. Finally, in clean room environments, contamination phenomena can spoil crop lots, with a consequent decrease in productivity. Using equipment that is less sensitive to contamination will reduce this risk. In conclusion, we can say that the Smart-Trak mass flow controllers (MFC) from the American company Sierra Instruments can perfectly perform this function.  

Most important features of the SMART-Track:

1. Thermal dispersion measurement technology gives a direct measurement of the mass flow rate, unaffected by variations in P and T.
2. Its capillary type measurement system provides great linearity of measurement regardless of the gas measured. Thanks to its digital electronics, the equipment is calibrated for 10 different gases.
3. Superior” measurement performance; accuracy +/- 1% full scale (for all gases), repeatability +/-0.2% f.s., and 50:1 rangeability.
4. It incorporates an automatic, frictionless, direct-acting control valve for fast and stable adjustment of the gas flow rate between 2 and 100% of the equipment range.
5. Compact in size, with high quality 316 stainless steel measuring body and multiple process connection types available

  For further information, please contact MATELCO, SA. e-mail: instrumentacion@matelco.es.