Xylooligosaccharides production by crude and partially purified xylanase from Aureobasidium pullulans: Biochemical and thermodynamic properties of the enzymes and their application in xylan hydrolysis

In this study, crude and partially purified xylanase from Aureobasidium pullulans CCT 1261 were characterized and applied in beechwood xylan hydrolysis to obtain xylooligosaccharides (XOS). Fractional precipitation (0–30 %/30–60 %) with ammonium sulfate allowed partial purification of xylanases in 6.8-fold and recovery of 69.4 %. Both extracts exhibited optimum activity at 50 °C and pH 4.5, and greater stability at 40 °C within the studied range. The thermostability parameters (kd, t1/2, ΔH*, ΔG*, ΔS*) of the extracts indicated the enzyme denaturation by the increment in temperature from 40 °C to 60 °C; its process was endothermic and led to protein unfolding in a more random structure. Crude xylanase showed a lower value of the Michaelis-Menten constant (25 mg/mL) than the partially purified enzyme (50 mg/mL). In hydrolysis reactions, total XOS contents (7.7 mg/mL and 7.9 mg/mL) and XOS yields (25.7 % and 26.5 %) were equal statistically using the crude or partially purified extracts, differing only in the amount of xylose released. The hydrolysates were mainly composed of potential prebiotics, i.e., xylobiose (50.9 % and 53.8 %) and xylotriose (30.9 % and 32.8 %). Based on these results, the use of crude and partially purified xylanase from A. pullulans showed a promising perspective for xylan hydrolysis to produce XOS.