High-Recovery Cell Broth Microfiltration with 0.22µm PES Cassette: A Case Study from Laboratory

1. Product Information

0.22μm PES membrane cassette, 0.1 m² (N2PE2308GA04)

 

2. Experimental Results

600 mL of cell fermentation broth was processed using a 0.22μm, 0.1 m² membrane cassette, concentrated down to 100 mL, followed by diafiltration with 5 diavolumes of purified water (i.e., 100 mL purified water per diafiltration step, repeated 5 times). After the 5th diafiltration, the batch was concentrated to the final volume. The total experiment took 34 minutes, yielding 48 mL of retentate and 1054.5 mL of total permeate, with an average flux of 18.6 LMH. Throughout the process, the retentate valve was fully open, and TMP ranged from 0.2 to 0.85 bar. Feed turbidity was 131 NTU, permeate turbidity was 3.13 NTU.

After use, the cassette was cleaned and regenerated. The change in water flux is shown in Table 1.

 

Table 1: Water Flux Recovery Rate

	Feed flow rate (mL/min)	Feed pressure (bar)	Retentate pressure (bar)	TMP(bar)	Permeate flow rate (mL/min)	LMH	Flux recovery (%)	Remarks
Before use	370	0.4	0	0.2	140	420	79	Retentate valve fully open
After cleaning	370	0.6	0	0.3	166	332		Retentate valve fully open

Note: Flux recovery calculated as 332/420 ≈ 79%.

Integrity test before and after experiment

Pressure hold test passed

Process conditions during the experiment are summarized in Table 2. Total runtime: 34 min.

 

Table 2: Process conditions over time

Time(min)	Feed flow (mL/min)	Feed pressure (bar)	Ret. pressure (bar)	TMP(bar)	Permeate flow (mL/min)	Remarks
0	200	1.5	0	0.75	32	Start; retentate valve fully open; 500 mL feed
5	200	1.2-1.4	0	0.6-0.7	33
10	200	1.0	0	0.5
10	200	1.6	0	0.8	25	+100mLfeed added
15	200	1.6	0	0.8	15
20	200	1.6-1.7	0	0.8-0.85	11
22	200	1.6-1.7	0	0.8-0.85	25	100 mL left; start 1st diafiltration with 100 mL purified water
25	200	1.3-1.4	0	0.65-0.7
26	200	1.0-1.1	0	0.5-0.55	43	100 mL left; 2nd diafiltration (+100 mL purified water)
27	200	0.6	0	0.3
28	200	0.5	0	0.25	53	100 mL left; 3rd diafiltration (+100 mL purified water)
30	200	0.4	0	0.2	61	100 mL left; 4th diafiltration (+100 mL purified water)
32	200	0.4	0	0.2	68	100 mL left; 5th diafiltration (+100 mL purified water)
34						End: 48 mL retentate (turbidity 345 NTU); total permeate 1054.5 mL (3.13 NTU); Concentration permeate 493.5 mL (2.58 NTU); First 3 diafiltration permeates 305 mL (3.03 NTU); Last 2 diafiltration permeates 256 mL (3.01 NTU)

 

 

Concentration phase:Feed pressure decreased over time; adding 100 mL feed caused pressure to rise then stabilize. Permeate flow dropped from 33 mL/min to 11 mL/min (~33% of initial).

Diafiltration phase: With purified water, feed pressure dropped significantly and flux increased notably.

Total processed volume: 1054.5 mL over 0.11 m² (0.1 m² nominal + correction); total time 34 min; average permeate flow 31 mL/min → average flux 18.6 LMH.

 

 

Figure 2: Feed vs. Permeate turbidity comparison (original image)

Feed turbidity 131 NTU, permeate turbidity 3.13 NTU.

 

 

Figure 3: SDS-PAGE gel electrophoresis

The SDS-PAGE result indicates target protein recovery >85% by the 0.22μm microfiltration cassette.

3. Experimental Methods

3.1 Installation

Install the system as shown in Figure 2

 

 

3.2 Water flux measurement

Use purified water as feed. Place feed tube into feed, retentate and permeate tubes into waste container. Start peristaltic pump, adjust diaphragm valve to achieve appropriate TMP until retentate and permeate are neutral (pH). Stop pump. Place feed, retentate and permeate tubes into purified water, start pump, wet membrane for 15 min. Stop pump, open diaphragm valve. Measure water flux: feed and retentate tubes in purified water, adjust to TMP1, collect permeate for 1 minute, calculate flux.

 

3.3 Integrity test (pressure hold / bubble test)

Remove feed tube from water, place retentate and permeate into waste. Run pump to empty liquid from lines, stop pump. Fully close retentate valve. Run pump to introduce air until feed pressure reaches 0.65 bar, stop pump. Observe pressure drop over 10 minutes and check permeate port for bubbles in water. If no pressure drop and no bubbles → integrity OK. If pressure drops and bubbles appear, measure air diffusion rate with flow meter or inverted water-filled cylinder; compare with reference value to assess integrity. Finally, fully open retentate valve and vent air.

 

3.4 Tangential flow filtration (TFF)

Process 600 mL cell fermentation broth with 0.22μm, 0.1 m² cassette, concentrate to 100 mL, then perform diafiltration with 5× volume purified water (100 mL each step). After the 5th diafiltration, concentrate further to final volume. After experiment, open retentate valve fully, drain liquid to recover retentate.

 

3.5 Cleaning

3.5.1 Water rinse

Use 10–20 L/m² purified water as feed. Feed tube in water, retentate and permeate to waste. Start pump, adjust TMP, run until feed lines are drained. Stop pump, open diaphragm valve.

3.5.2 Caustic cleaning

Use 0.5 M NaOH as feed. Place feed, retentate and permeate tubes into the NaOH solution. Start pump, adjust TMP, circulate for 30–60 min. Stop pump, open diaphragm valve.

 

3.6 Post-cleaning water flux measurement

Same as 3.2, using same TMP (TMP2 = TMP1). Measure permeate volume over 1 minute and calculate flux.

 

3.7 Post-cleaning integrity test

Same as 3.3.

 

3.8 Storage

Prepare 0.1 M NaOH solution as storage medium. Place feed, retentate and permeate tubes into the solution. Start pump, adjust TMP, circulate for 5 minutes. Stop pump, open diaphragm valve. Remove cassette from system and store in 0.1 M NaOH at room temperature.

 

This case study demonstrates efficient microfiltration of high-turbidity cell culture broth using a 0.22µm PES membrane cassette. Key benefits:

High product recovery (>85% by SDS-PAGE)

Rapid processing– 34 minutes for 600 mL with diafiltration

Excellent turbidity reduction – from 131 NTU to 3.13 NTU permeate

Good cleanability – 79% water flux recovery after simple caustic cleaning

Integrity assurance– passed pressure hold test before and after use

 

The cassette maintained consistent performance, with diafiltration causing a sharp drop in TMP and corresponding flux increase, demonstrating low fouling propensity and easy rinsing. Ideal for concentrating and desalting fermentation broths, cell culture supernatants, and other bioprocess streams.