| Description: |
Exopolysaccharides of microbial origin provide, thanks to their technological and functional properties, an extraordinary opportunity for the development of new food products with high added value. Although microbial EPS are known to enhance the sensory and health-related characteristics of foods, it is still a field that requires further scientific analysis, especially in relation to the need to increase yields and clarify some aspects related to their interactions with the gut microbiota. Thus, the primary goal of this Ph.D. project was to isolate and characterize novel microbial EPS produced by LAB with desirable bioactivities for the development of new functional food products. First, LAB were isolated from fermented foods and screened for EPS production to identify the highest performers (Chapter 2). Through a qualitative and quantitative approach, twelve strains of LAB, including Lb. plantarum, Lb. paracasei, Lc. lactis, and Leuc. mesenteroides, were identified, which could produce more than one gram of EPS per liter. The initial step of the research has revealed three Leuconostoc strains that produced the highest yields. These strains have been used as the basis of Chapter 3, Chapter 4, and Chapter 5, where the EPS were analyzed in-depth with regards to their chemical, morphological, and functional properties. An EPS produced by Leuc. mesenteroides B3, isolated from an Italian semi-hard cheese, was identified as a mixture of two dextrans having different Mw. This EPS was shown to have potential as an antimicrobial and antibiofilm agent, especially against L. monocytogenes. It also stimulated bifidobacteria, potentially making them more robust during food processing and storage (Chapter 3). This EPS from Leuc. mesenteroides F02A5, isolated from raw milk cheese, is a high-Mw dextran with a linear structure. EPS displayed antimicrobial activity against some foodborne pathogens, as well as radical scavenging capacity. Moreover, the polymer was characterized by high solubility and capacity to retain water, ... |