Living Emulsions: Role and Functionality of Active Bacteria in Multiphase Systems

Living emulsions, which incorporate active bacteria into oil–water multiphase systems, represent an innovative integration of microbiology and colloid science. The active role of living species offers dynamic and adaptive functionalities absent in traditional emulsions. In particular, bacteria, as active colloids, have the potential to fulfill roles such as Pickering stabilizers, biomanufacturers, and biomediators to functionalize, reinforce, or degrade with multiphasic components. Selecting bacteria with appropriate surface properties (e.g., wettability, surface charge) enables their adsorption at oil–water interfaces, forming living Pickering emulsions for food or biocatalyst applications. Beyond static stabilization, bacteria-driven biosynthesis of materials like bacterial nanocellulose (BNC) at interfaces could promote advanced biofabrication of structured microcapsules and emulgels; whereas, conversely, hydrocarbon-degrading bacteria have been recognized to disrupt emulsions by metabolizing oil phases, offering bioremediation solutions for oil spills. These active emulsion systems highlight bacterial adaptability to extreme conditions and biodegradability, aligning with ecological sustainability. By merging microbial activity with emulsion science, living emulsions unlock smart, multifunctional systems for industries ranging from food to environmental technology.