Isolation, screening and characterization of a novel extracellular xylanase from Aspergillus niger (KP874102.1) and its application in orange peel hydrolysis

Abstract

In the present work, a potent xylanase producing fungal strain Aspergillus niger (KP874102.1) was isolated through cultural and morphological observations from soil sample of Baramura forest, Tripura west, India. 28S rDNA technique was applied for genomic identification of this fungal strain. The isolated strain was found to be phylogenetically closely related to Aspergillus niger. Kinetic constants such as K_m and V_max for extracellular xylanase were determined using various substrate such as beech wood xylan, oat spelt xylan and CM cellulose through Lineweaver-Burk plot. K_m, V_max and K_cat for beech wood xylan are found to be 2.89mg/ml, 2442U and 426178Umlmg^-1 respectively. Crude enzyme did not show also CM cellulose activity. The relative efficiency of oat spelt xylan was found to be 0.819 with respect to beech wood xylan. After acid hydrolysis, enzyme was able to produce reducing sugar with 17.7, 35.5, 50.8 and 65% (w/w) from orange peel after 15, 30, 45 and 60min incubation with cellulase free xylanase and maximum reducing sugar formation rate was found to be 55.96μg/ml/min. Therefore, the Aspergillus niger (KP874102.1) is considered as a potential candidate for enzymatic hydrolysis of orange peel.

Keywords: 28S rDNA technique; Cellulose free xylanase; Characterization; Enzyme hydrolysis; Isolation; Kinetics; Molecular characterization; Xylanase.