Tuneable Pickering emulsions stabilised by bacterial cellulose

Bacterial cellulose (BC) is a sustainable and highly pure alternative to plant-derived nanocellulose. An emerging application of BC lies in emulsion stabilisation, where its biodegradability, non-toxicity and biocompatibility may alleviate environmental and health concerns of conventional surfactants. This work presents a systematic comparison of short (C6) and long chain acyl chloride (C12) modification of once dried BC as a starting material, where the degree of surface modification was controlled by varying reaction time. The resulting BC fibres exhibited tuneable surface wettability, enabling BC to function as an emulsion stabiliser for oil-in-water (o/w) and water-in-oil (w/o) emulsions. Emulsion droplet size, stability and rheological behaviour were evaluated as a function of fibre concentration, oil-to-water ratio, oil type, pH, ionic strength and temperature. Eucalyptus oil emulsions showed optimal stabilisation at fibre concentrations of 1% (w/v) and droplet diameters of 5.6 μm and 3.8 μm for w/o systems formed using hexanoyl chloride and lauroyl chloride treated fibres, respectively. Additional oils, including olive oil, caprylic oil, dodecane and hexadecane, were also examined. The results demonstrate that BC provides dual emulsion capability, highlighting its potential as an emulsifier for Pickering emulsion systems.