Separation of lactic acid-producing bacteria from fermentation broth using a ceramic microfiltration membrane with...

Area of Science:

• Biochemical Engineering
• Separation Science
• Membrane Technology

Background:

• Microfiltration is crucial for separating microorganisms in bioprocessing.
• Critical flux is a key parameter determining membrane performance and fouling.
• Lactic acid bacteria separation presents challenges due to cell properties and broth composition.

Purpose of the Study:

• To investigate the influence of operating parameters on critical flux for lactic acid bacteria microfiltration.
• To understand the role of crossflow velocity, cell concentration, protein concentration, and pH.
• To evaluate the impact of membrane isoelectric point (IEP) on separation efficiency.

Main Methods:

• Ceramic microfiltration membrane with a permeate pump was utilized.
• Systematic variation of crossflow velocity, bacterial cell concentration, protein concentration, and pH.
• Analysis of critical flux under different operating conditions and membrane IEPs.

Main Results:

• Critical flux increased with crossflow velocity (5.3-10.8 m/s).
• Bacterial cell concentration (1.1-3.1 g/L) did not affect critical flux.
• Increased protein concentration reduced critical flux due to membrane adsorption.
• Lowering pH (to 4-5) drastically decreased critical flux by promoting bacterial adhesion.
• Membrane IEP significantly influenced critical flux, with lower IEPs reducing flux.

Conclusions:

• Crossflow velocity and protein concentration are critical factors in optimizing microfiltration of lactic acid bacteria.
• pH-dependent bacterial physiology and membrane-surface interactions play a vital role in fouling and flux reduction.
• Membrane selection based on IEP is crucial for efficient separation, particularly in acidic fermentation broths.