Oligosaccharide Synthesis in Fruit Juice Concentrates Using a Glucansucrase From Lactobacillus reuteri 180

• GTF180 glucansucrase produces α-glucooligosaccharides in fruit juice concentrates.
• >90% of the intrinsic sucrose was converted after 90 min at the optimum conditions.
• Different α1→6/α1→3 ratios in the enzymatically treated concentrates were found.
• This is the first report of α1→2 glycosidic linkages formation by this enzyme.

The application of the glucansucrase GTF180 from Lactobacillus reuteri 180 in fruit juice concentrates for the synthesis of glucooligosaccharides was investigated. Reaction parameters such as temperature, pH, substrate and enzyme loading, Ca+2 addition and incubation time were investigated in high concentration sucrose solutions. The optimum conditions (50 °C, pH 4.5, enzyme loading 14.47 U/gsucrose with 1 mM CaCl2, undiluted fruit juice concentrates) were applied in apple and orange juice concentrates. More than 95% of the intrinsic sucrose was converted to oligosaccharide products after 90 min. The main products were leucrose, isomaltose and isomaltotriose. The enzyme was deactivated during standard fruit juice pasteurization conditions (95 °C, 15 s). The oligosaccharides were stable during the pasteurization process, showing a good potential for industrial applications. DOSY NMR analysis of the enzymatically modified fruit juice concentrates showed that α1→6 glycosidic linkages are predominant in apple juice, while products in orange juice possess both α1→6 and α1→3 glycosidic linkages. The presence of α1→2 glycosidic linkages were also observed at a lower extent.