Activity and partial characterisation of xylanolytic enzymes in the earthworm Eisenia andrei fed on organic wastes

This study demonstrates the occurrence of active xylanolytic enzymes in extracts from Eisenia andrei, Bouché 1972. Xylanase was the most active enzyme (2.06 U g−1), followed by acetyl xylan esterase (0.55 U g−1). Lower activities showed β-d-glucuronidase (0.17 U g−1), α-l-arabinosidase (0.04 U g−1) and β-xylosidase (0.03 U g−1). All of the xylanolytic enzymes displayed higher total activity when the earthworms were fed on a xylan-containing medium. Xylanase, α-l-arabinosidase and acetyl xylan esterase showed maximal activity at neutral pH. In contrast, β-xylosidase and β-glucuronidase displayed maximal activity at pH 3.0 and 4.0, respectively. All enzymes displayed a high activity within the physiological temperature range 35 to 40°C. Km and Vmax values of xylanolytic enzymes were also estimated. Kinetic parameters for xylanase were determined in extracts of earthworms fed on standard medium (Km=6.91±1.120 mg ml−1; Vmax=0.05±0.002 U mg−1), and in extracts of earthworms fed on a medium containing xylan (Km=5.60±1.070 mg ml−1; Vmax=0.12±0.006 U mg−1).