Abstract. Fructooligosaccharides (FOS) are additives that are often used and utilized in the food, pharmaceutical, and chemical industries that have functional value for health. Lactobacillus plantarum B1765 has been known to have inulinase activity. This research aimed to further explore the potential of L.plantarum B1765 in the production of FOS from lesser yam tuber inulin by looking at the total growth of lactic acid bacteria (LAB) and the degree of polymerization (DP) during a certain

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... ntation time. The duration of fermentation was carried out for 24, 48, and 72 hours. The testing of Total LAB using total plate count (TPC) method with MRS Agar medium. The Testing determination of total sugar and reduction sugar using the Nelson Somogyi method. Determination of the degree of polymerization (DP) of the formed FOS is based on the result of dividing the total sugar formed with the reducing sugar released during the fermentation process. The results of total LAB that grows from each fermentation time is 2,11×107; 1,55 ×108; and 3,3 ×109 CFU/mL, with degree of polymerization formed from each fermentation time are 3,470; 2,286; and 1,740. Comercial FOS has a DP value of 3-5. This study was able to produce a commercially acceptable fructooligosaccharide with a DP of 3,470, which could be used for industrial development of fermented lesser yam tuber fructooligosaccharides. Key words: Lactobacillus plantarum B1765, lesser yam tuber, inulin, FOS, degree of Polymerization