The rapid global decline of coral reefs has intensified the need for innovative conservation strategies, including the use of microbial therapies to enhance coral health and resilience. A major limitation, however, is the lack of effective delivery systems for administering beneficial microorganisms for corals (BMCs). In this study, we present natural, biodegradable alginate-based delivery systems (beads, hydrogels, and macrofibers) loaded with the probiotic Pseudoalteromonas peptidolytica as a model microorganism. Probiotic encapsulation efficiency reached 7.33 × 10⁴ ± 2.5 × 10³ CFU/g of polymer, with mechanical characterizations demonstrating that all systems maintained structural stability upon initial introduction to salt water. In vitro diffusion assays demonstrated that the encapsulated probiotic strain remained viable, proliferative, and capable of migrating beyond its delivery vehicles. After an initial lag phase, the release of probiotics increased sharply and peaked at 24 hours. Scanning electron microscopy confirmed the release of probiotics concurrent with the degradation of the alginate matrix. In subsequent in vivo experiments, to confirm the specificity of the alginate-based systems and compare their probiotic delivery performance, fragments were collected from all samples for PCR and Illumina sequencing of V4 region of the taxonomic marker gene 16S RNA. The microbiome analyses confirmed a partial probiotic uptake following deployment of the alginate systems and suggested that the introduced strains may persist over time. Microbiome analysis and energy-dispersive X-ray spectroscopy (EDX) indicated that degradation of all three delivery systems was driven by a combination of biological and chemical mechanisms. As the first underwater delivery systems specifically engineered for coral probiotics, these alginate-based materials provide a promising foundation for advancing microbial therapy applications in both controlled aquaria and natural reef environments.
Facchinelli, M., Contardi, M., Caldwell, J., Ghizzi, I., Calabretta, V., Gandolfi, I., et al. (2026). EXPLORING ENHANCED UNDERWATER DELIVERY OF PROBIOTICS TO POCILLOPORA DAMICORNIS. Intervento presentato a: Corals, Coasts and One Health - 14 - 16 February 2026, KAUST, Saudi Arabia.
EXPLORING ENHANCED UNDERWATER DELIVERY OF PROBIOTICS TO POCILLOPORA DAMICORNIS
Facchinelli, M;Contardi, M;Ghizzi, I;Calabretta, V;Gandolfi, I;Galli, P;Montano, S;
2026
Abstract
The rapid global decline of coral reefs has intensified the need for innovative conservation strategies, including the use of microbial therapies to enhance coral health and resilience. A major limitation, however, is the lack of effective delivery systems for administering beneficial microorganisms for corals (BMCs). In this study, we present natural, biodegradable alginate-based delivery systems (beads, hydrogels, and macrofibers) loaded with the probiotic Pseudoalteromonas peptidolytica as a model microorganism. Probiotic encapsulation efficiency reached 7.33 × 10⁴ ± 2.5 × 10³ CFU/g of polymer, with mechanical characterizations demonstrating that all systems maintained structural stability upon initial introduction to salt water. In vitro diffusion assays demonstrated that the encapsulated probiotic strain remained viable, proliferative, and capable of migrating beyond its delivery vehicles. After an initial lag phase, the release of probiotics increased sharply and peaked at 24 hours. Scanning electron microscopy confirmed the release of probiotics concurrent with the degradation of the alginate matrix. In subsequent in vivo experiments, to confirm the specificity of the alginate-based systems and compare their probiotic delivery performance, fragments were collected from all samples for PCR and Illumina sequencing of V4 region of the taxonomic marker gene 16S RNA. The microbiome analyses confirmed a partial probiotic uptake following deployment of the alginate systems and suggested that the introduced strains may persist over time. Microbiome analysis and energy-dispersive X-ray spectroscopy (EDX) indicated that degradation of all three delivery systems was driven by a combination of biological and chemical mechanisms. As the first underwater delivery systems specifically engineered for coral probiotics, these alginate-based materials provide a promising foundation for advancing microbial therapy applications in both controlled aquaria and natural reef environments.
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