Question: A fermentation broth is being produced at the rate of 2500 liter/hr. It has cells, cell debris along with the two main biomacromolecules as products, a monoclonal antibody (MAb) of molecular weight (MW) 245,000 and a protein of MW 18,000; it also has a small MW product (MW,400) along with salt (0.2 wt%).
The allowed impurity levels in the MAb product are: 200 times lower than the feed level for the 400 MW product; 250 times lower than the feed level for salt.The MAb and the protein are each present in the feed at the level of 2 mg/ml of solution; the 400 M.W. product is present in the feed at the level of 1 g/liter.The allowed impurity levels in the protein product are: 200 times lower than the feed level entering the protein separation device (PSD) for the 400 MW product; 200 times lower than the feed level to the PSD for salt.
The MAb product will be ultimately purified further by ion exchange chromatography.An adsorption process is available for purifying the 400 MW product (vis-à-vis the salt) which is adsorbed by the adsorbent. The adsorbent bed is regenerated by an aqueous stream having a different temperature.The fermentation broth clarification is to be done either by a filter press or a rotary vacuum filter. The final purification of the 400 MW product in an aqueous solution takes place by crystallization.
Develop a process schematic diagram. Assume that this process is continuous.
Show each product stream illustrating the impurity level with respect to the feed entering the particular separator.
There will be separate process product streams: the 245,000 MW MAb purified; the 18,000 MW protein purified; an aqueous solution containing the 400 MW product in reasonably purified form. Your process schematic ultimately must lead to crystals of the 400 MW product. Add comments to justify your selection of the components of the process schematic.
(1) You have to calculate how much filter press area is needed to process the fermentation broth at the rate at which it is being produced. You have to account for an amount of filter press downtime equal to the production time per 1500 liter for cleaning purposes. Given: Information on the fermentation broth properties, filter press operation and the filter cake properties: The fermentation broth has 2.4 % solids (~24.1 kg/m3) and a viscosity of ~2.25 cp at 25°C. The filter medium resistance may be neglected vis-à-vis the cake resistance. The cake may be assumed to be incompressible. The value of Cs for the cake filtration process is 4.75 x 106 kN-sec/m4. The filtrate viscosity may be assumed to be that of water. The filtration operation is carried out at 25°C. The applied pressure difference is 425 kN/m2.
(2) For the given concentrations of the monoclonal antibody, the small molecular weight product and the coloring contaminant in the filtrate, develop a mass balance for a continuous diafiltration step and indicate the volumetric flow rates and concentrations of different species in the different streams obtained. Determine the membrane area needed. Given: Membrane properties and mass transfer information: Diafiltration: MWCO of the membrane - 50,000; R300 = 0; Rcoloring matter = 0; RmAb = 0.98; the diafiltration process may be assumed to be such that the protein mass transfer coefficient is 2.5 x 10-5cm/sec throughout diafiltration step; gel polarization with complete protein rejection may be assumed for flux calculation even though it is avoided in diafiltration: also (Cigel/Cilb) = 10. Assume negligible loss of products in the filter press.