SOYBEAN PROTEIN AS ENCAPSULATING AGENT OF PROBIOTIC ENTEROCOCCUS

LOPEZ RIZO, MARIA CAROLINA; ABEIJON MUKDSI, MARIA CLAUDIA; PEREZ CHAIA, ADRIANA

San Miguel de Tucumán

Simposio; V Simposio Internacional de Bacterias Lácticas; 2016

Centro de Referencia para Lactobacilos (CERELA)-CONICET

Microencapsulation is a technique widely applied in functional food field to transport probiotic microorganisms to their target site, protecting them from adverse conditions of the gastrointestinal tract (GIT). Soybean production is one of the main economic activities in our region, thus the use of soybean protein isolates (SPI) as encapsulating agent is of great interest. The formulation of micro and nanoparticles using soybean globular proteins is a novel strategy for vehiculization of probiotic microorganisms or bioactive compounds through the GIT of the host, allowing them to reach their target site viable and active. The aim of this study was to isolate soybean globular proteins from commercial soybean pellet, evaluate its capacity as encapsulation matrix of a probiotic strain, and assess resistance of microencapsulated cells to GIT conditions. SPI was obtained by aqueous extraction and precipitation at pH 4.5, and its purity was assessed by electrophoresis (SDS-PAGE). Microparticles were formed by mixing Enterococcus faecium LET 301 suspension (probiotic strain from avian intestine; ~108 cfu/mL) with SPI, and adding CaCl2 in different concentrations. As control, bacterial suspension was replaced by sterile saline solution. Particle stability, sedimentation time and morphology were evaluated. Encapsulation efficiency was calculated from viable cell counts in original bacterial suspension and remaining non-encapsulated cells. Strain resistance to GIT conditions was evaluated by sequential incubation of encapsulated and free cells in simulated gastric and intestinal juices. SPI extraction protocol was very efficient, yielding 30 mg protein/mL. Electrophoretic patterns revealed intense bands corresponding to subunits α, α' and β from 7S fraction (β-conglycinin) and the acidic and basic subunits from 11S fraction (β-conglycinin), which represent 80% of soybean globular protein, thus indicating a high degree of purity. When preparing SPI particles, almost instantaneous formation was observed after adding CaCl2 at a final concentration of 4.8 and 9.6 mM, but not 2.4 mM. Particles were stable upon overnight storage at 4 °C. No significant differences were observed between particles with bacteria and control. Based on their sedimentation degree, particles formed at higher CaCl2 concentration seemed to have larger size. By microscopic examination, particles showed irregular shape and bacterial cells entrapped inside them. The encapsulation efficiency of E. faecium LET 301 in SPI matrix was 98.9%. Encapsulated cells presented higher resistance to GIT conditions than free cells. Particles were disintegrated at simulated intestinal conditions, releasing entrapped cells. Our results validate our SPI extraction protocol and support the potential use of soybean globular proteins as encapsulation matrix of probiotic microorganisms.