Demulsification of Bacteria-Stabilized Pickering Emulsions Using Modified Silica Nanoparticles

Area of Science:

• Colloid and Surface Science
• Biotechnology
• Chemical Engineering

Background:

• Bacteria-stabilized Pickering emulsions are promising for microbial transformations of hydrophobic compounds.
• High emulsion stability poses challenges for downstream processing, and current demulsification methods have drawbacks.

Purpose of the Study:

• To develop a practical method for demulsifying bacteria-stabilized Pickering emulsions.
• To investigate the use of chemically modified fumed silica particles for demulsification.
• To apply this strategy to the demulsification of emulsions used in sterol microbial transformations.

Main Methods:

• Studied demulsification of W/O Pickering emulsions stabilized by *Mycobacterium neoaurum* using fumed silica particles with varying hydrophobicity.
• Analyzed emulsion type, droplet morphology, and dewatering rates influenced by silica particle hydrophobicity and concentration.
• Utilized confocal microscopy to investigate particle interactions at the emulsion interface.

Main Results:

• Chemically modified silica particles induced phase inversion and dewatering of bacteria-stabilized Pickering emulsions.
• Silica particle hydrophobicity and concentration were key parameters controlling emulsion properties and dewatering efficiency.
• Competitive adsorption between bacteria and silica particles at the interface was observed, leading to bacterial detachment.

Conclusions:

• The average hydrophobicity of particles at the interface dictates emulsion type and stability.
• Addition of a second particle emulsifier (silica) provides an effective strategy for Pickering emulsion demulsification.
• This method enables successful product and organic phase separation after microbial transformation in Pickering emulsions.