Cold and salt stress modulate amount, molecular and macromolecular structure of a Lactobacillus sakei dextran

In-situ exopolysaccharide (EPS) formation by starter cultures is frequently exploited in the dairy-industry, where they function as natural hydrocolloids and improve both rheological and textural characteristics of these food products. In contrast, applications in fermented meat products remain widely unexplored neglecting beneficial effects such as fat replacement or enhanced serum binding capacity. Since amount and structure of EPS determine their functional effects in foods, we investigated the impact of cold and salt stress, which are important parameters in the manufacturing of meat products, for their impact on quantity and structural properties of the dextran produced by Lactobacillus sakei TMW 1.411. Upon growth under different (stress) conditions, the amount of dextran was lowest (0.5 g/L) at 30 degrees C/9.5% NaCl, while about fourfold increased amounts were obtained at 10 degrees C/0% NaCl (6.7 g/L) compared to 30 degrees C/0% NaCl (1.6 g/L). The highest molecular weights and particle sizes were determined for the dextran produced at 10 degrees C/0% NaCl, which displayed a decreased degree of branching. Comparable results regarding amounts and sizes were obtained when dextrans were produced by resting cells in buffers under the same conditions used during growth experiments in mMRS media. Our data suggest that amount, molecular and macromolecular structure of extracellular dextrans produced by Lactobacillus sakei TMW 1.411 are markedly influenced by the applied temperature, while high salt concentrations strongly limit dextran polymerization from sucrose. These findings provide new insights into possible future applications aiming at an in-situ EPS formation in meat-based food products with improved properties. (C) 2018 Elsevier Ltd. All rights reserved.