GELLAN GUM MICROPARTICLES FOR INTESTINE-TARGETED DELIVERY OF PROBIOTICS

This study focuses on developing carriers for probiotic formulations to create innovative functional foods. Among biobased polymers, gellan gum was chosen for encapsulating probiotic microorganisms due to its widespread use as a gelling agent in various foods and as an agar substitute for microbiological plate assays. Additionally, gellan gum microparticles have demonstrated cryoprotective and gastroretentive properties. Lactobacillus Fermentum was used as model probiotic for this work. Gellan gum microparticles were produced by electrohydrodinamic microdripping. Gellan gum powder was disselved in distilled water at different concentrations (0.5, 1, 1.25 %wt) by stirring at 90°C. Solutions were autoclaved and pumped throug a stainless steel needle (positive high voltage). Microparticles were directly collected in 20 mL of 1%wt CaCl2 crosslinking bath (grounded). L. Fermentum was inoculated in De Man, Rogosa and Sharpe (MRS) broth and plated on MRS agar to determine colony-forming units (CFU). Bacterial suspensions were prepared determining OD600, centrifuged and resuspended in 1% wt gellan gum (GG1), to achieve probiotic loads of 106 CFU/mL (GG1-low) and 109 CFU/mL (GG1-high). GG1-low was re-incubated in MRS broth for 24 and 48h, and stained with Syto9 fluorescent dye to assess bacterial growth inside the particles. A 1% wt gellan gum solution was identified and tested for probiotic entrapment. Wet particle size distributions were systematically studied at an optimized flow rate (1 mL/h) and voltage (25 kV) to evaluate the effect of probiotic inclusion. Empty particles had a mean size of 250 ± 50 µm, while GG1-low (106 CFU/mL) and GG1-high (109 CFU/mL) had sizes of 300 ± 40 µm and 450 ± 100 µm, respectively. Plating of the particles showed high probiotic viability post-encapsulation. Plating of the crosslinking bath after filtration displayed at least 2-log units less CFU with respect the dripped ones, indicating high encapsulation efficiency. The obtained particles exhibited a size range suitable for the food industry, and various concentrations of microorganisms were successfully trapped inside the hydrogel matrix. Re-incubation of GG1-low and Syto9 staining demonstrated the ability of probiotics to grow both inside and on the surface of the particles. Overall, the tested processes proved effective for directly encapsulating high probiotic loads and regrowing probiotics within the particles. The latter method may potentially be utilized to produce particles containing both high loads of probiotics and postbiotics in a single formulation.