Enzymatic synthesis of propionyl-fructooligosaccharides and their evaluation as a gut microbiota modulator

Propionic acid (PA), an end product of bacterial metabolism, has various functions in the colon. The aim of this study was to use ester bonds to link PA and a prebiotic fructooligosaccharides (FOS) to form propionyl-FOS capable of delivering PA to the colon. We used enzyme assistance and acid anhydride method to produce propionyl-FOS, respectively. FT-IR and NMR were used to confirm the formation of ester bonds. MALDI-TOF-MS was used to characterize the ester diversity and to partly monitor the fate of propionyl-FOS. In vitro simulated gut fermentation was used to study the effect of obtained esters on gut microbiota modulation and metabolite production. Our results showed that chemically synthesized propionyl-FOS (AP-FOS) was propionyl-esterified to a higher degree than enzymatically synthesized ones (P-FOS). Propionyl-fructooligosaccharides were more diverse in AP-FOS than in P-FOS. Higher levels of PA and butyric acid were detected in both AP-FOS and P-FOS groups than in FOS group after 24 h in vitro fermentation. The fermentability and prebiotic effects of AP-FOS were lower than those of P-FOS due to the high esterification degree of the former. Compared to FOS, P-FOS could confer better beneficial health effects through gut microbiota modulation. Hence, enzymatically synthesized P-FOS could be a potential prebiotic for health-promoting properties.