Enzymatic properties and straw-degrading effect of a xylanase derived from rumen

Abstract:

[Objective] To investigate the enzymatic properties and straw-degrading effect of a recombinant xylanase rRuXyn024.[Methods] We cloned RuXyn024 from the rumen of beef cattle and used bioinformatics tools for detailed sequence analysis.The expression vector pET-RuXyn024 was constructed and transformed into Escherichia coli BL21(DE3) for heterologous expression of RuXyn024.Furthermore,the enzymatic properties and straw-degrading effect of rRuXyn024 were examined.[Results] RuXyn024 was composed of 358 amino acid residues and had a molecular weight of approximately 40 kDa,belonging to the GH 10 family.The optimal pH and temperature of rRuXyn024 were pH 7.0 and 40℃,respectively.The relative activity of RuXyn024 at pH 6.0−9.0 and 30−70℃ remained above 60% and 70%,respectively.With xylan from wheat straw as the substrate,rRuXyn024 showcased the K_m and V_max of 18.8 g/L and 82.6µg/min,respectively.The activity of rRuXyn024 was inhibited by Mg²⁺,Zn²⁺,Cu²⁺,Ni²⁺,EDTA,and SDS at 1 mmol/L and 5 mmol/L,as well as 5 mmol/L Ca²⁺ and β-mercaptoethanol.Cu²⁺ and β-mercaptoethanol at 5 mmol/L nearly inactivated the enzyme.Mn²⁺ at 1 mmol/L and 5 mmol/L increased the activity of rRuXyn024 by 46.9% and 35.8%,respectively.The degradation of xylan from wheat straw by rRuXyn024 produced oligosaccharides,including xylotriose and xylobiose.rRuXyn024 could degrade maize straw,rice straw,soybean straw,and rapeseed straw,with the strongest degrading effect on maize straw.[Conclusion] rRuXyn024 exhibits tolerance to broad scopes of pH and temperature and significant potential for improving the utilization of straw by ruminants.

Key words:xylanase;enzymatic properties;straw;degrading effect