Measurement of Microbial Protease Activity Using a pH-Stat Titration

Area of Science:

• Enzymology
• Microbiology
• Biochemistry

Background:

• Protease activity is crucial in various industrial and biological processes.
• Accurate and sensitive measurement of protease activity is essential for research and development.
• Existing methods like the trinitrobenzenesulfonic acid (TNBS) assay have limitations.

Purpose of the Study:

• To compare the efficacy of the pH-stat titration method and the TNBS method for measuring microbial protease activity.
• To evaluate the sensitivity, speed, and repeatability of both methods.
• To determine the optimal method for proteases with varying pH activity profiles.

Main Methods:

• Purified and crude microbial proteases were analyzed.
• Activity was measured using an automatic pH-stat instrument at pH 9.
• The pH-stat titration method was directly compared with the TNBS method.
• Repeatability and linear correlation (R²=0.985) were assessed.

Main Results:

• The pH-stat titration method yielded higher activity measurements than the TNBS method for purified Bacillus amyloliquefaciens protease.
• Both methods showed excellent repeatability (C.V.=2.6%).
• The pH-stat method demonstrated greater sensitivity and indicated higher proteolytic activity for Pseudomonas spp. with optimal activity at pH 9.

Conclusions:

• The pH-stat titration method is simpler, faster, and more sensitive than the TNBS method for determining protease activity, particularly for enzymes with optimal activity at or above pH 9.
• The pH-stat method provides a more accurate assessment of protease activity in certain microbial samples.
• This finding has implications for optimizing enzyme assays in industrial and research settings.