Bengoa Ana Agustina, Dueñas María Teresa, Prieto Alicia, Garrote Graciela L, Abraham Analía G
Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CIDCA) (CONICET-UNLP-CIC), Buenos Aires, Argentina.
Dpto. de Química Aplicada, Facultad de Química, Universidad del País Vasco (UPV/EHU), San Sebastián, Spain.
Front Microbiol. 2023 Feb 24;14:1110177. doi: 10.3389/fmicb.2023.1110177. eCollection 2023.
Exopolysaccharides (EPS) produced by lactic acid bacteria are molecules of great interest for the dairy food industry. CIDCA 8339, CIDCA 83123, and CIDCA 83124 are potentially probiotic strains isolated from kefir grains whose EPS-production on MRS broth is dependent on incubation temperature. The aim of the present work is to evaluate the effect of fermentation temperature on the characteristics of EPS produced in milk by strains and the consequent impact on the rheological properties of the fermented products. Additionally, the protective effect of these EPS against infection was evaluated . Acid gels with each strain were obtained by milk fermentation at 20°C, 30°C, and 37°C evidencing for all the strains a reduction in growth and acidification rate at lower temperature. CIDCA 83123 showed low fermentation rate at all temperatures requiring between 3 and 8 days to obtain acids gels, whereas CIDCA 8339 and 83124 needed between 24 and 48 h even when the temperature was 20°C. Fermentation temperature led to changes in crude EPS characteristics of the three strains, observing an increase in the relative amount of the high molecular weight fraction when the fermentation temperature diminished. Additionally, EPS and EPS presented modifications in monosaccharide composition, with a reduction of rhamnose and an increase of amino-sugars as temperature rise. These changes in the structure of EPS resulted in an increase of the apparent viscosity of milks fermented at 20°C (223 mPa.s) and 30°C (217 mPa.s) with respect to acid gels obtained at 37°C (167 mPa.s). In order to deepen the knowledge on EPS characteristics, monosaccharide composition of low and high molecular weight EPS fractions were evaluated. Finally, it was evidenced that the preincubation of intestinal epithelial cells Caco-2/TC-7 with EPS and EPS partially inhibit the association and invasion of . In light of these results, it can be concluded that the selection of the EPS-producing strain along with the appropriate fermentation conditions could be an interesting strategy to improve the technological properties of these fermented milks with potential protective effects against intestinal pathogens.
乳酸菌产生的胞外多糖（EPS）是乳制品行业非常感兴趣的分子。CIDCA 8339、CIDCA 83123和CIDCA 83124是从开菲尔粒中分离出的潜在益生菌菌株，它们在MRS肉汤中产生EPS的能力取决于培养温度。本研究的目的是评估发酵温度对这些菌株在牛奶中产生的EPS特性的影响，以及对发酵产品流变学特性的后续影响。此外，还评估了这些EPS对感染的保护作用。通过在20°C、30°C和37°C下对牛奶进行发酵，获得了含有每种菌株的酸性凝胶，结果表明，在较低温度下，所有菌株的生长和酸化速率均降低。CIDCA 83123在所有温度下发酵速率都很低，需要3至8天才能获得酸性凝胶，而CIDCA 8339和83124即使在20°C的温度下也只需24至48小时。发酵温度导致这三种菌株的粗EPS特性发生变化，当发酵温度降低时，观察到高分子量部分的相对含量增加。此外，随着温度升高，EPS和EPS的单糖组成发生了变化，鼠李糖减少，氨基糖增加。EPS结构的这些变化导致在20°C（223 mPa·s）和30°C（217 mPa·s）下发酵的牛奶的表观粘度相对于在37°C（167 mPa·s）下获得的酸性凝胶有所增加。为了深入了解EPS的特性，对低分子量和高分子量EPS部分的单糖组成进行了评估。最后，有证据表明，用EPS和EPS对肠上皮细胞Caco-2/TC-7进行预孵育可部分抑制的黏附和侵袭。根据这些结果，可以得出结论认为，选择产生EPS的菌株并结合适当的发酵条件，可能是一种有趣的策略，可改善这些发酵乳的技术特性，并对肠道病原体具有潜在的保护作用。
