Isolation, morphological & molecular characterization of Aspergillus species producing α-L-Rhamnosidase from Agro-Industrial waste

An α-L-rhamnosidase enzyme [E.C.3.2.1.40] has potential application in food and pharmaceutical industry. Naringin is the dominant flavanoid bitter compound found in citrus fruit juices of the objective of present study was to isolate α-L-rhamnosidase producing fungus, study their morphological and molecular characteristics. A total twelve fungal strains were isolated from agro-industrial waste of lemon and sweet lemon peels for α-L-rhamnosidase enzyme production. Of these, only 4 isolates were capable of producing the α-L-rhamnosidase enzyme to hydrolyze naringin for removal of bitter taste from juices. Fungal isolates were selected according to their higher α-L-rhamnosidase enzyme activities (3.481 IU mL⁻¹). For morphological studies, macroscopic features like colony colour, texture, elevation, growth and margins as well as microscopic characteristics such as the size of conidia and conidiophores, and their arrangements were examined for species differentiation. DNA was isolated from the best α-L-rhamnosidase producing fungal strain, and amplification of 18S rRNA gene, using specific primers ITS-1 and ITS-4 was done. This gene was subsequently sequenced and phylogenetic affiliations was accordingly assigned. Fungal isolate was identified as Aspergillus flavus.