Production of feruloylated arabino-oligosaccharides (FA-AOs) from beet fiber by hydrothermal treatment

Beet fiber is a fibrous by-product of the beet sugar industry. Efficient production of arabino-oligosaccharides (AOs) and feruloylated arabino-oligosaccharides (FA-AOs), which are AOs esterified with ferulic acid, from beet fiber was investigated. Under hydrothermal conditions at a reaction temperature from 160 °C to 180 °C for a reaction time of 5–15 min, solubilization of the beet fiber occurred in the range of 58–63 wt%. In the soluble fraction, galactose and arabinose as well as their oligomers have been detected. It is notable that various characteristic glycosides, which consist of ferulic acid and AOs or galacto-oligosaccharides (GOs), were obtained from the arabinan or galactan side chains of the pectin present in the beet fiber. The total yield of AOs and FA-AOs reached 84% at 160 °C for 12 min, which was determined as arabinose units contained in the beet fiber. Almost all the ferulic acid present in the beet fiber was recovered as ferulate esters of oligosaccharides such as AOs or GOs via hydrothermal treatment.

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► Almost all the ferulic acid contained in the beet fiber was recovered as ferulate esters of oligosaccharides under hydrothermal conditions.
► The acquired AOs and FA-AOs were identified using MALDI-TOF MS analysis, following fractionation using a hydrophobic adsorbent.
► The optimum reaction conditions for recovery of AOs and FA-AOs included a temperature in the range from 160 °C to 170 °C and a reaction time of 5–15 min.