Standard Operating Procedure for pH Monitoring and Adjustment in Bioreactor Operations for Biosimilars

Department	Biosimilars
SOP No.	SOP/BS/069/2025
Supersedes	SOP/BS/069/2022
Page No.	Page 1 of 12
Issue Date	04/05/2025
Effective Date	06/05/2025
Review Date	04/05/2026

1. Purpose

To provide a standardized procedure for monitoring and adjusting pH in bioreactors during biosimilar manufacturing processes, ensuring optimal cell growth conditions and GMP compliance.

2. Scope

This SOP applies to all production bioreactors used in upstream processing of biosimilars, including stainless steel and single-use systems ranging from 10L to 2000L.

3. Responsibilities

• Process Operators: Monitor pH in real time and perform adjustments as per protocol.
• Maintenance Team: Calibrate pH probes and ensure operational status of pH control loops.
• QA Personnel: Review logs and verify adherence to validated pH ranges.

4. Accountability

The Head of Upstream Production is accountable for maintaining pH control within the defined range and ensuring appropriate documentation and calibration status.

5. Procedure

5.1 Calibration of pH Probes

1. Calibrate pH probes using 2-point calibration with certified buffer solutions (pH 4.0 and 7.0) prior to batch start (Annexure-1).
2. Ensure calibration is logged and probe tags match bioreactor configuration.

5.2 Setpoint Configuration

1. Set desired pH range on the bioreactor control panel (typically 6.8–7.2 for mammalian cells).
2. Verify PID settings for acid/base addition systems are in automatic mode.

5.3 Real-Time pH Monitoring

1. Monitor pH via bioreactor software interface every 2 hours.
2. Log actual values, trends, and any deviation in the pH Monitoring Log (Annexure-2).
3. If automated system is offline, perform manual sampling and check with handheld pH meter.

5.4 pH Adjustment Procedure

1. If pH falls below setpoint:
   • Use sterile 1N NaOH for upward correction through automated or manual ports.
2. If pH exceeds setpoint:
   • Use sterile 1N HCl or CO₂ sparging for downward correction.
3. Adjust slowly and monitor impact in 10-minute intervals to avoid overshoot.

5.5 Alarm Management

1. In case of pH deviation beyond ±0.2 units:
   • Trigger alarm and initiate deviation handling (SOP/BS/050/2025).
   • Verify if probe fouling or drift occurred; perform re-calibration if required.

5.6 End-of-Run Procedure

1. Record final pH and probe status in End-of-Run Summary (Annexure-3).
2. Clean pH sensor as per SOP/BS/098/2025 and store in pH 4.0 buffer.

6. Abbreviations

• PID: Proportional-Integral-Derivative
• QA: Quality Assurance
• GMP: Good Manufacturing Practice

7. Documents

1. pH Probe Calibration Log – Annexure-1
2. pH Monitoring Log Sheet – Annexure-2
3. End-of-Run pH Summary – Annexure-3

8. References

• ICH Q7 – Good Manufacturing Practice for Active Pharmaceutical Ingredients
• WHO TRS 1010 – Guidelines on Biotherapeutics
• SOP/BS/050/2025 – Deviation Handling
• SOP/BS/098/2025 – pH Sensor Maintenance

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: pH Probe Calibration Log

Probe ID	Calibration Date	Buffer Used	Calibrated By
PH-BR-01	03/05/2025	pH 4.0 & 7.0	Sunita Reddy

Annexure-2: pH Monitoring Log Sheet

Date	Time	Setpoint	Actual pH	Remarks
04/05/2025	12:00	7.0	7.02	Within limit

Annexure-3: End-of-Run pH Summary

Batch ID	Final pH	Deviation Noted	Corrective Action
BR-109	6.98	No	N/A

Revision History:

Revision Date	Revision No.	Revision Details	Reason for Revision	Approved By
04/05/2025	2.0	Added Annexure-3 and CO₂ adjustment for high pH	Process Optimization