Production of xylooligosaccharides from hardwood xylan by using immobilized endoxylanase of Clostridium strain BOH3

Abstract

Prebiotic xylooligosaccharides (XOS) are indispensable components in food preparations. Thus, developing a cost-effective process for XOS production is important to meet increasing market demands. In this study, an endoxylanase excreted by a solventogenic Clostridium strain BOH3 is exploited to hydrolyze xylan and produce XOS with a high yield. Furthermore, a technique is developed to immobilize the endoxylanase in calcium alginate gel beads to produce XOS from hardwood xylan. In addition to calcium alginate, the gel beads also contain 3.5% w/v of silica gel, which increases the hardness by 1.6 times and significantly reduces leaching of xylanase from the beads. As a result, the immobilized xylanase can be reused for 7 cycles while retaining >62% of its initial activity. Moreover, when beechwood and teakwood xylans are used as substrates, the immobilized xylanase liberates only xylobiose and xylotriose. This phenomenon is distinctly different from free xylanase which releases a wide range of XOS. Overall, the immobilized xylanase can produce 0.37–0.48 mg of XOS (per mg of xylan). The XOS produced by immobilized xylanase shows prebiotic effects on Bifidobacterium animalis, and Lactobacillus acidophilus.