Building microcompartments using chitosan-stabilized water-in-water emulsion as templates for microbial cultivation

In this study, chitosan-stabilized water in water (W/W) emulsions had been fabricated by using polyethylene oxide (PEO) and maltodextrin (MD) to encapsulate Lactobacillus plantarum for high-density culture. Systematic investigations had been conducted to evaluate the effects of chitosan viscosity, concentration, MRS broth concentration, ionic strength, and pH on the stability of the emulsions. The chitosan-stabilized W/W emulsions demonstrated high stability across diverse environmental conditions, exhibiting no phase separation after 7 days storage even at minimal chitosan concentrations of 0.02 wt% (weight percentage, wt%). Notably, the pH-responsive chitosan-stabilized W/W emulsions maintained structural integrity for 30 days at pH 6.0. The semi-permeable characteristics of W/W interfaces enabled efficient nutrient uptake and metabolite exchange, facilitating successful encapsulation and cultivation of Lactobacillus plantarum within the emulsion matrix. Optimal cultivation was achieved using emulsions containing 1.0 wt% MRS broth, yielding a peak viable cell count of 1.09 × 10⁹ CFU/mL. These findings demonstrated that chitosan-stabilized W/W emulsions hold significant potential for probiotic protection and the development of microreactors enabling high-density microbial cultivation.