Ultrasound-assisted fabrication of synbiotic microcapsules based on gum arabic and oligosaccharides for C. butyricum delivery: characterization, stress tolerance, and storage stability.

A novel ultrasound-assisted synbiotic microencapsulation system was developed using gum arabic, reconstituted skim milk, and prebiotic oligosaccharides (fructooligosaccharides, xylooligosaccharides, and galactooligosaccharides) for the delivery of Clostridium butyricum. Ultrasound significantly improved viable-cell recovery, reaching 93.17 % in the fructooligosaccharide formulation (p < 0.05). Structural analyses indicated that oligosaccharide type and ultrasound treatment affected particle morphology, water mobility, protein secondary structure, and the solvent-extractable fractions related to intermolecular interactions. Ultrasound treatment improved the environmental stress tolerance of the freeze-dried formulations, increasing 60-day storage survival by 10.4 %, 6.9 %, and 16.6 % in the control, XOS, and GOS formulations, respectively, and significantly reducing viability loss during separate gastric, intestinal, and bile-salt tolerance tests (p < 0.05). Among the tested oligosaccharides, the XOS-containing formulations showed the most balanced overall performance. MC-XOS showed the highest survival after heat treatment (51.3 %) and retained a survival rate of 27.5% after 3  h of separate exposure to simulated gastric fluid, whereas MC-XOS-US maintained the highest survival after 60  days of storage at 4 °C (60.87 %) (p < 0.05). These findings provide an effective strategy for developing stable delivery systems for anaerobic probiotics.