Production of tailored xylo-oligosaccharides from beechwood xylan by different enzyme membrane reactors and evaluation of their prebiotic activity

Abstract

Xylo-oligosaccharides (XOs) from xylans are gaining interest due to their wide use in food, feed and pharmaceutical industry. In this work, the enzymatic production of XOs from beechwood xylan in batch, continuous and semi-continuous enzyme membrane reactor mode was compared. The potential of an inline viscometer for real-time monitoring of the hydrolysis was assessed as well. In all modes, an initial concentration of 7% (w/w) beechwood xylan was applied at a temperature of 50 °C and a pH of 5.8. Initially, the effect of enzyme dosage was investigated in batch mode (0.5, 2.6, 12, 26 and 720 U of Cellic®CTec2.g−1 xylan). Higher enzyme dosages led to a faster hydrolysis rate, but also to an undesirable higher production of xylose. The introduction of enzyme membrane reactors allowed production of XOs with weight average molecular weights of ca. 5–8.9 kDa combined with negligible xylose quantities (<3% in freeze dried product). The semi-continuous configuration has the edge in comparison to the full continuous configuration in terms of enzyme consumption and ease of operation. In vitro fermentations with three different gut bacteria were performed and confirmed the prebiotic properties of the produced XOs with average degree of polymerization of 48.