Microencapsulation of Bacillus subtilis and oat β-glucan and their application as a synbiotic in fish feed

Abstract

To improve survival during storage and exposure to adverse conditions, Bacillus subtilis was microencapsulated with oat β-glucan by spray-drying technology. The characterisation of the microcapsules was designed to compare free and microencapsulated cells through exposure to simulated gastric fluids (SGF) throughout storage for 90 days at different temperatures. The characterisation included analysis of efficiency, morphology, moisture, water activity, hygroscopicity, particle size, and zeta potential. The microcapsules presented a particle size of 1.5 ± 0.34 μm and an encapsulation efficiency of 77.9 ± 3.06%. After SGF, the survival of microencapsulated cells was 8.4 ± 0.07 log CFU mL⁻¹ while that of free cells was 7.6 ± 0.06 log CFU mL⁻¹. After 90 days of storage, only microencapsulated cells remained above 6 log-unit of viability. In conclusion, spray-drying technique combined with the addition of oat β-glucan proved to be an efficient method to protect B. subtilis under storage and SGF with potential application in fish feed.

Keywords:

• Atomization
• gastrointestinal tolerance
• microencapsulation
• probiotics
• prebiotics

Acknowledgements

Pluridisciplinary Center for Chemical, Biological and Agricultural Research (CPQBA—Unicamp) is gratefully acknowledged for their help during the spray-drying procedure and the in vitro batch culture experiments. Institute of Biology (IB—Unicamp) is gratefully acknowledged for their help during the analysis of zeta potential.

Geolocation information

22°42′24.4″S 47°38′28.2″W.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by “Fundação de Amparo à Pesquisa do Estado de São Paulo” (São Paulo State Research Foundation—FAPESP), grant number 2020/04215–5, and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), grant number 88.887.353035/2019–00.