Enhancing xanthine oxidase fermentation with pH-shift strategy based on kinetic analysis by Arthrobacter M3

Area of Science:

• Biotechnology
• Enzyme Production
• Microbial Fermentation

Background:

• Xanthine oxidase (XOD) is an important enzyme with various applications.
• Optimizing fermentation conditions is crucial for maximizing enzyme yield.
• Previous studies identified optimal initial pH and inducer concentration for XOD fermentation.

Purpose of the Study:

• To investigate the effect of initial culture pH and inducer concentration on XOD fermentation.
• To implement and evaluate a pH-shift strategy for enhanced XOD production in batch fermentation.
• To model XOD production and substrate consumption using kinetic equations.

Main Methods:

• Shake flask experiments to determine optimal initial pH (8.6) and inducer concentration (3.6 g/l).
• Batch fermentation of XOD by Arthrobacter M3 in a 7.5-l fermentor under varying pH conditions (7.6-8.6).
• Implementation of a pH-shift strategy: initial pH 8.6, shifted to 7.6 upon reaching 2.0 g/l dry cell weight (DCW).
• Kinetic modeling using the Luedeking-Piret equation for product accumulation and a Luedeking-Piret-like equation for substrate consumption.

Main Results:

• Optimal initial conditions: pH 8.6 and 3.6 g/l inducer concentration.
• The pH-shift strategy significantly enhanced XOD production (7,415.3 U/l) and yield coefficient (1,229.7 U/g) compared to other protocols.
• Luedeking-Piret models accurately described product accumulation (R²=0.977) and substrate consumption (R²=0.992).

Conclusions:

• A pH-shift strategy is highly effective for enhancing xanthine oxidase fermentation in Arthrobacter M3.
• The optimized fermentation process achieved significantly higher XOD yields.
• Kinetic modeling provides a robust framework for understanding and optimizing microbial fermentation processes.