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 ℃,moreover,XynA remains above 80％of the activity at pH value ranging from 5.0 to 10.5 and temperatures between 45 and 75℃.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.
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