Immobilization of Lactic acid bacteria for production of extracellular polysaccharides

Lactic acid bacteria (LAB) can produce extracellular polysaccharides that can be used as thickeners, emulsifiers, and gels in foods. The immobilization technology can effectively simplify and improve the separation and regeneration of extracellular polysaccharides. In this study, six strains of LAB, including the extracellular polysaccharide-producing strain Lactobacillus plantarum, were screened. The different immobilized carriers of sodium alginate, agar, gelatin-glutaraldehyde, and carrageenan were assessed for fermentation by these six LAB. Different diameters of beads were selected, and the optimum culture temperature, carrier concentration, and inoculum volume were evaluated. The results showed that the agar-embedding method was the best immobilization method and the optimum process conditions were as follows: 3% inoculum of L. plantarum, 30 g/L of agar as immobilization carrier with a particle diameter of 1 cm, and fermentation at 37 degrees C for 24 h. Through orthogonal experiments, the maximum exopolysaccharide (EPS) yield obtained was 1489.9 mg/L.