α-l-Arabinofuranosidase from Streptomyces sp. PC22: Purification, characterization and its synergistic action with xylanolytic enzymes in the degradation of xylan and agricultural residues
2008
α-l-Arabinofuranosidase was purified from culture filtrates of the thermoalkaliphilic Streptomyces sp. PC22 to about 108-fold purity by (NH₄)₂SO₄ precipitation followed by column chromatography. Its approximate molecular weight was 404kDa, with a subunit mass of ~79kDa. The evaluated K m and V max values with p-nitrophenyl-α-l-arabinofuranoside as substrate were 0.23mM and 124 U·mg⁻¹, respectively. The purified enzyme was optimally active at 65°C and pH 6.0 and showed a mild but significant synergistic effect in combination with other xylanolytic enzymes, including xylanase, β-xylosidase and acetyl esterase, on the degradation of oat-spelt xylan, corn cob and corn husk substrates with a 1.25, 1.32 and 1.21-fold increase in the amount of reducing sugar released, respectively, compared to the expected (additive) amounts for the individual enzymes acting alone. Sequential reactions using two xylan-backbone degrading enzymes (xylanase/β-xylosidase) and two debranching enzymes (α-l-arabinofuranosidase/acetyl esterase) were also determined. The highest degree of synergy was obtained in sequential reactions with the debranching enzyme digestion preceding the xylan-backbone degrading enzymes.
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