Sequential fermentative production, physicochemical, and prebiotic properties of purified neokestose using Daw longan (Dimocarpus longan L. cv. Daw) as the sole substrate

• Longan is a potential fermentation medium for the direct production of neokestose • Yeast treatment could be directly applied to fermentative neokestose • Yeast treatment could effectively remove simple sugars from neokestose • The physicochemical properties of the purified neokestose promote its use as syrup • In vitro cytotoxicity has indicated the safety of neokestose Neokestose is the shortest chain fructooligosaccharide possessing prebiotic properties. The aims of this research were to develop a simple fermentation process for the production and purification of neokestose using longan fruit pulp extract (LFPE) as simple fermentation medium. LFPE was fermented by Xanthophyllomyces dendrorhous TISTR 5730. Once the fermentation process attained maximal neokestose content, prior to being sequentially fermented by Candida orthopsilosis FLA44.2, the fermentation broth was heated to inactivate the cells and 6G-fructofuranosidase, thereby establishing the selective removal of simple sugar residues from the produced neokestose. Induction of seed inoculum by sucrose for both X. dendrorhous TISTR 5730 and C. orthopsilosis FLA44.2 helped shorten the time-consuming process for neokestose production and purification, respectively. Under optimal conditions, neokestose content of 104.86 ± 2.30 g/L and a purity value of 98.3% were produced from LFPE. After partial decolorization, deodorization, and concentration, the neokestose appeared as yellow to amber in color and possessed the physicochemical properties of syrup. Moreover, it was resistant to simulated gastrointestinal conditions and was fermentable by the tested probiotics. Due to its sweetness, prebiotic properties, and a reduction in calories, the resulting neokestose could be considered a beneficial multifunctional syrup, particularly for people diagnosed with obesity and diabetes.