Isolation and Characterization of Inulin from Sweet Potato (Ipomoea batatas L. Cilembu) with Maggot Frass Fertilization as Prebiotic in Synbiotic Yoghurt

Cilembu sweet potato (Ipomoea batatas L. Cilembu) has a sweet potato with high inulin content. However, sweetness and inulin content decrease if sweet potatoes are planted outside the optimal environment. Thus, this study aimed to test the effect of maggot frass fertilizer on the inulin content of Cilembu sweet potato and evaluate its bioactivity as a prebiotic. The research methods included inulin isolation from Cilembu sweet potato, inulin identification, prebiotic activity test, yoghurt starter production, synbiotic yoghurt fermentation, and yoghurt analysis. Inulin was isolated by precipitation using a mixture of ethanol and water to obtain inulin powder yields of different fertilization doses: 0 (P1), 5 (P2), and 10 (P3) kg/5 m2, of 10.01, 21.07, and 22.97%, respectively. The results of in vitro prebiotic activity tests have shown an increase in the growth of Lactobacillus bugaricus and Streptococcus thermophilus. Inulin powder from sweet potato increased the viability of lactic acid bacteria in synbiotic yoghurt, with the highest increase at P3 dose with 5% inulin concentration (2.5 × 109 cfu/mL), highlighting its potential as a probiotic. In conclusion, maggot frass fertilizer increased the inulin content in Cilembu sweet potato and prebiotic activity in yoghurt.