Abstract
Two exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) strains, Liquorilactobacillus (L.) sp CUPV281 and Liquorilactobacillus (L.) mali CUPV271, were isolated from Spanish apple must. Each of the strains produced a dextran, with different branching degrees, to be incorporated into soy protein isolate (SPI) film-forming formulations. Films were prepared by compression molding, a more rapid processing method than solution casting and, thus, with a greater potential for scaling-up production. Thermal analysis showed that SPI and EPS start the degradation process at temperatures above 190 °C, confirming that the compression temperature selected (120 °C) was well below the corresponding degradation temperatures. Resulting films were transparent and homogeneous, as shown by UV-Vis spectroscopy and SEM, indicating the good compatibility between SPI and EPS. Furthermore, FTIR analysis showed that the interactions between SPI and EPS were physical interactions, probably by hydrogen bonding among the polar groups of SPI and EPS. Regarding antifungal/fungistatic activity, LAB strains used in this study showed an inhibitory effect on germination of fungal spores.
Highlights
Exopolysaccharides (EPS) are polysaccharides secreted by bacteria into the extracellular matrix, or they can remain loosely associated to the cell surface by electrostatic interactions
It is worth noting that all films showed high L* values, indicatingcolor the lightness control andofEPS-incorporated films
Results suggest that the inhibitory effect of our lactic acid bacteria (LAB) strains on germination of fungal spores is not caused by EPS production and that culture conditions favoring EPS production stimulate filamentous fungal growth
Summary
Exopolysaccharides (EPS) are polysaccharides secreted by bacteria into the extracellular matrix, or they can remain loosely associated to the cell surface by electrostatic interactions. Among EPS, homopolysaccharides, containing only one type of monomer, or heteropolysaccharides, with two or more different monosaccharides, can be found [1] These biodegradable polymers have high molecular weights and relevant physiological functions [2]. Some EPS, such as dextrans, produced by lactic acid bacteria, are considered as generally recognized as safe (GRAS) substances as defined by the US. These biopolymers are employed for thickening, gelling, emulsification, stabilization, crystallization prevention, fat replacement, encapsulation, dough rheology and food texture improvement [6,7,8,9,10] Beside food industry, they are used as cosmeceuticals, herbicides and insecticides [11,12]
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