# DBT JRF 2020 — Question 100

Exam: DBT JRF 2020 · Section: B · Topic: Bioprocess Engineering · Difficulty: Hard

## Question

Aqueous two phase partitioning (ATPS) is used for the recovery of an enzyme from the cell free culture filtrate. On addition of PEG-2000 and dextran, the mixture separates into two phases with a partition coefficient for the enzyme as 4.2. The maximum possible enzyme recovery, when the volume ratio of the upper to lower phases is 5.0, will be

## Options

- **A.** 76%
- **B.** 85%
- **C.** 95%
- **D.** 68%

## Answer

Option C

## Explanation

ATPS (Aqueous Two-Phase System) recovery calculation: The system separates into upper phase (PEG-rich, volume $V_u$ ) and lower phase (dextran-rich, volume $V_l$ ). Partition coefficient $K = \dfrac{C_u}{C_l}$ (concentration in upper/lower phase). Volume ratio $r = \dfrac{V_u}{V_l} = 5.0$ . Total enzyme = $C_u V_u + C_l V_l$ . Enzyme in upper phase = $C_u V_u = K C_l V_u = K r C_l V_l$ . Recovery in upper phase $= \dfrac{K r}{K r + 1} \times 100\% = \dfrac{4.2 \times 5.0}{4.2 \times 5.0 + 1} \times 100\% = \dfrac{21}{22} \times 100\% \approx 95.5\% \approx 95\%$ .

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