Part I Process Schematic:
A fermentation broth being produced at the rate of 1500 liter/hr has two extracellular products of interest, a monoclonal antibody of molecular weight 145,000 and a small molecular weight product (M.W. 300). The broth also has a coloring contaminant of molecular weight 250 at the level of 0.4 wt%. The monoclonal antibody is present at the level of 1 mg/ml of solution; the 300 M.W. product is present at the level of 3 gm/liter. It is known that if the coloring contaminant level can be reduced by 200 times then the monoclonal antibody product will be okay; similarly for the small molecular weight product vis-à-vis the monoclonal antibody product (which will be ultimately purified by ion exchange chromatography; but that is not your concern). On the other hand, an adsorption process is available for purifying the smaller molecular weight product vis-à-vis the coloring contaminant which is adsorbed by the adsorbent. The bed loaded with the coloring contaminant 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) or a cylindrical centrifuge. Your process schematic must show both clarification methods as alternate ways of clarifying the fermentation broth. After the coloring contaminant is substantially removed, the final purification of the 300 dalton product in an
aqueous solution takes place by crystallization.
Develop a process schematic which will yield separate process streams: the 145,000 molecular weight monoclonal antibody purified and in an aqueous solution; an aqueous solution of the small molecular weight (300 dalton) product in reasonably purified form; the coloring contaminant in a hot aqueous solution. Your process schematic ultimately must lead to crystals of the small molecular weight product. Add comments to justify your selection of the components of the process schematic.
Part II: Preliminary Design Calculations:
(1) You have to find out 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 μ α 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.