After a large screening on sourdough lactic acid bacteria, exopolysaccharide (EPS)-forming strains of Weissella cibaria, Lactobacillus plantarum, and Pediococcus pentosaceus were selected. After 6 days of incubation at 30 degrees C, the synthesis of EPS in MRS-based broth ranged from 5.54 to 7.88 mg mL-1. EPS had an apparent molecular mass of ca. 104 Da. As shown by carbohydrate consumption, the synthesis of EPS was found from sucrose only. Two types of homopolysaccharides were synthesized: glucans simultaneously with growth and fructans after 1 day of incubation. Two protein bands of ca. 180-200 kDa were in situ detected on SDS-PAGE gels incubated with sucrose. PCR products of ca. 220 bp were found for L. plantarum PL9 (100% of identity to putative priming glycosyltransferase of L. plantarum WCFS1) and W. cibaria WC4 (80% of identity to putative glycosyltransferase, epsD, of Bacillus cereus G9241) by using hybrid primers for the priming gtf genes. Degenerated primers DexreuR and DexreuV showed a unique PCR product, and the predicted amino acid sequences were identical for W. cibaria WC4 and L. plantarum PL9. The sequence had similarity with polysaccharide biosynthesis glycosyltransferases. W. cibaria WC4 or L. plantarum LP9 synthesized ca. 2.5 g kg-1 EPS during sourdough fermentation with sucrose added. Compared to the sourdough started with an EPS-negative strain, the sourdough started with W. cibaria WC4 or L. plantarum LP9 increased the viscosity, and the resulting bread had higher specific volume and lower firmness. The synthesis of EPS by selected sourdough lactic acid bacteria could be considered as a useful tool to replace the additives for improving the textural properties of baked goods.

Ambient storage of dry powdered probiotics is necessary for manufacturer's cost reduction and customer's convenience. Complex coacervation is a promising microencapsulation technique. In this work, a probiotic matrix of type-A gelatin/gum arabic/sucrose (GE/GA/S) with high coacervation pH was designed, based on the alkaline isoelectric point of type-A gelatin. Bacterial survival during ambient storage at room temperature and certain relative humidity were detected. To clarify the protection factors of the coacervation matrix of GE/GA/S, dry microcapsules of GA, GE, GE/sucrose and GE/GA were prepared as controls and compared in terms of their morphology, moisture content, dynamic vapor absorption and cell viability. Probiotics in GE/GA/S microcapsules behaved the best during spray drying, ambient storage and heat treatment. The results proved that sucrose addition was necessary for cell viability against environmental stresses, and that encapsulation by complex coacervation was a positive factor in cell protection, especially at neutral coacervation pH.

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