Isolation and
characterization of derhamnosylating alkaline α-L-rhamnosidase from Aspergillus
niger
Kunwar Vishal, Shukla Aparna and Yadav Pramod K.
Res. J. Biotech.; Vol. 20(8); 120-127;
doi: https://doi.org/10.25303/208rjbt1200127; (2025)
Abstract
α-L-Rhamnosidases are ubiquitous enzymes responsible for derhamnosylation of α-L-rhamnose
moiety from a variety of glycoconjugates including rutin, naringin, hesperidin,
quercitrin, terpenyl glycosides and numerous other natural glycosides. An α-L-rhamnosidase-secreting
fungal strain was isolated from a soil sample collected at a local fruit market.
This strain was initially identified as Aspergillus sp. through lactophenol cotton
blue staining and later confirmed as Aspergillus niger via ITS gene sequencing.
The rhamnosidase activity of the fungal strain was screened on modified Czapek-Dox
agar medium supplemented with naringin.
Enzyme production was assessed in liquid culture medium containing naringin, rutin
and hesperidin as inducers. The optimal pH and temperature for maximum catalytic
efficiency of the crude α-L-rhamnosidase were found to be pH 10.0 and 70°C respectively.
The Michaelis constant (Km) and maximum velocity (Vmax) for the crude enzyme towards
naringin were determined to be 0.042 mM and 0.062 μmol min⁻¹ ml⁻¹ respectively.
