Co-cultivation of selected Lactiplantibacillus plantarum strains with starter cultures under osmotic stress increases folate content and enhances product quality in fermented dairy

Abstract

This study aimed to identify lactic acid bacteria (LAB) strains with high folate production potential to enhance the folate content in fermented dairy products. From 284 LAB strains sourced from fermented vegetables and dairy, six were selected for their outstanding folate production. Among these, Lactiplantibacillus plantarum TXZ2-26 and L. plantarum FJ2-3 demonstrated strong synergistic interactions with the starter culture, resulting in an increased total LAB cell count after co-cultivation. The effects of five different stress conditions on the growth, folate production, and expression of key folate-synthesis genes (folE, folP, folQ, folB, folK) in the two strains were further examined, revealing that the two strains demonstrated increased folate production under 3% NaCl stress. Finally, both unstressed and NaCl-stressed strains were used in the fermentation of goat and cow milk alongside the starter culture. The results revealed that the addition of L. plantarum TXZ2-26 and FJ2-3 significantly boosted the folate content of the fermented dairy products and improved their physicochemical properties, with the stressed strains exhibiting a more pronounced effect. These findings underscore the potential of L. plantarum TXZ2-26 and FJ2-3 as effective probiotics for producing folate-enriched fermented foods.