Heterologous expression and characterization of xylanase XynA from Geobacillus stearothermophilus and antioxidant activity of Xylo-oligosaccharides.

The experiment aims to develop xylanase XynA and provide a new resource for feeding xylanase. The XynA of Geobacillus stearothermophilus was heterologous expressed in Pichia pastoris, the optimal fermentation conditions, enzymatic properties and antioxidant properties of the hydrolysis product Xylo-oligosaccharide (XOS) were studied. The results showed that the crude XynA with enzyme activity of about 33.7 U/mL could be produced after 96 h induced by 1.0% methanol concentration. The optimum pH value of XynA is 9.0, the optimum temperature is 65 °C, moreover, XynA remains above 80% of the activity at pH value ranging from 5.0 to 10.5 and temperatures between 45 and 75 °C. Thin-layer chromatography (TLC) analysis revealed that the main products of the hydrolysis of bagasse xylan by XynA were xylotriose and xylohexaose. The scavenging rate of DPPH free radical reached 72.04% and the scavenging rate of hydroxylradical reached 99.16% with 1 000 mg/L XOS. The study indicates that XynA exhibits robust activity and stability, efficiently hydrolyzing xylan to produce XOS, thereby facilitating its application in the feed industry. [ABSTRACT FROM AUTHOR]