Selection and characterization of exopolysaccharide producing lactic acid bacteria as potential food starter cultures

Lactic acid bacteria (LAB) play a vital role in the production of fermented foods, with certain strains being capable of producing exopolysaccharides (EPS) that may enhance the texture and functionality of fermented food products. Among these, bacterial β-glucan produced by LAB - a specific type of EPS - offers favorable rheological properties and potential health benefits, making it particularly valuable for food applications. In this study, a combined phenotypic and genotypic screening strategy was used to identify LAB strains potentially capable of producing β-glucan and suitable for use in food fermentations, with an emphasis on fruit-based products. From a collection of 246 LAB isolates, six EPS-producing strains harboring the gtf-2 gene, which encodes β-glucan synthase, were selected for further characterization. Notably, Lacticaseibacillus paracasei LTH 2407, isolated from Gouda cheese, is the first known member of its genus carrying a gtf-2 gene. Genomic and metabolic analyses revealed strain-specific profiles related to sugar transport, carbohydrate metabolism, and EPS biosynthesis, indicating their potential applicability in diverse food matrices, including fruit fermentations. A genome-based safety assessment showed no evidence of toxin production, antimicrobial resistance genes, or the genetic potential for producing highly toxic biogenic amines such as histamine or tyramine. These findings support the potential suitability of the selected strains for safe use as starter cultures in food fermentations. The study provides a solid basis for further analysis of the fermentation performance, EPS production capacity, and industrial relevance of these β-glucan-producing LAB strains.