Production of Nanocellulose from Kombucha SCOBY by Acid and Enzymatic Hydrolysis and Application as Pickering Emulsions Stabilizers

The symbiotic culture of bacteria and yeast (SCOBY) is a cellulose-rich biofilm generated during kombucha fermentation and represents an underutilized by-product with considerable biotechnological potential. This study aimed to produce and characterize nanocellulose from SCOBY through acid (BNCA) and enzymatic (BNCE) hydrolysis and evaluate its performance as a Pickering emulsion stabilizer. The materials were characterized by dynamic light scattering (DLS), zeta potential, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), contact angle measurements, and interfacial tension. Acid hydrolysis yielded nanocellulose with a high crystallinity index (CrI ≈ 89.4%), a relatively narrow particle size distribution, and a zeta potential of −46.4 mV, indicating good electrostatic colloidal stability. These properties were associated with favorable interfacial characteristics and an emulsification index (EI) of 100%. The enzymatic hydrolysis produced a cellulose with lower crystallinity, broader particle size distributions, and zeta potential values ranging from −10.2 to −30.9 mV, indicating reduced colloidal stability. Nevertheless, BNCE exhibited amphiphilic behavior and successfully stabilized oil-in-water Pickering emulsions, particularly after 24 h of hydrolysis (EI ≈ 96%). Contact angle measurements confirmed the hydrophilic character of both materials (water contact angles < 30°), supporting their potential for oil-in-water emulsification. Thermogravimetric analysis revealed that acid-hydrolyzed nanocellulose degraded at lower temperatures, potentially due to surface sulfate groups, whereas enzymatically hydrolyzed nanocellulose exhibited greater thermal stability. Overall, SCOBY-derived nanocellulose is a promising bio-based Pickering stabilizer. Although acid hydrolysis yielded materials with superior physicochemical properties, enzymatic hydrolysis offers an environmentally friendly alternative, warranting further optimization for sustainable food applications.