The aqueous two-phase system in Example 13-3 will be used in a batch extraction. \(7.5 \mathrm{~kg}\) of PEG solution contains protein at mass fraction \(\mathrm{x}_{\mathrm{F}}\). Use \(6.0 \mathrm{~kg}\) of pure dextran solution to extract the protein from the solution. Equilibrium data are in Example 13-3.

Example 13-3

a. Find fractional recovery of protein in dextran phase if two solutions are mixed and then allowed to settle.

b. Find fractional recovery of protein in dextran phase if continuous solvent addition batch extraction system shown in Figure 13-12 is used.

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We wish to extract a dilute solution of the protein alcohol dehydrogenase from an aqueous solution of 5 wt% poly (ethylene glycol) (PEG) with an aqueous solution that is 10 wt% dextran. Aqueous two-phase extraction is a very gentle method of recovering proteins that is unlikely to denature the protein, since both phases are aqueous (Albertsson et al., 1990; Harrison et al., 2015). The two phases can be considered to be essentially immiscible. The dextran phase is denser and will be the crossflow solvent. The entering dextran phases contain no protein. The entering PEG phase flow rate is 20 kg/h. a. If 10 kg/h of dextran phase is added to a single-stage extractor, find the total recovery fraction of alcohol dehydrogenase in the dextran solvent phase. b. If 10 kg/h of dextran phase is added to each stage of a crossflow cascade with two stages, find the total recovery fraction of alcohol dehydrogenase in the dextran solvent phase. The protein distribution coefficient is (Harrison et al., 2015) Kd = (wt fraction protein in PEG, x)/(wt fraction protein in dextran, y) = 0.12