To prepare functional yacon juice, this study investigates the optimal fermentation duration, shelf-life, chemical composition, and flavor volatiles of yacon juice fermented by Lactiplantibacillus plantarum QS7T capable of utilizing fructo-oligosaccharides (FOS), along with its effects on gut microbiota. The optimal fermentation period was determined as 30 h, resulting in essential parameters: 3.46 g L