Improving Folate Bioaccessibility and Modulating Gut Microbiota Profile with Folate-Enriched Purple Cabbage Juice by Optimized Lactiplantibacillus plantarum Fermentation

Abstract

Folate biofortification of plant-based foods via lactic acid bacteria fermentation is a strategy to alleviate folate deficiency; however, the effects of fermentation on folate stability and bioaccessibility remain unclear. In this study, purple cabbage juice was fermented with Lactiplantibacillus plantarum strains (1.1797 and YaXin) to enhance folate production, particularly 5-methyltetrahydrofolate (5-MTHF). Sucrose supplementation significantly promoted folate biosynthesis, with strain 1.1797 exhibiting the highest accumulation (210.69 ng/mL; 75–140% increase). Total folate showed limited storage stability and followed first-order degradation kinetics, while tea polyphenols improved folate stability by up to 38%. In vitro digestion demonstrated that strain 1.1797 increased total folate bioaccessibility by 40%, whereas YaXin showed lower bioaccessibility of approximately 8%. Colonic fermentation enhanced short-chain fatty acid production and modulated the gut microbiota, including enrichment of Firmicutes and Bifidobacterium. These findings highlight fermentation coupled with antioxidant stabilization as a strategy to improve folate functionality in plant-based beverages.