Screening and Identification of Laccase Producing Fungi from Environmental Samples

Abstract

Laccases are oxidases with broad substrate specificity and ability to oxidize various phenolic and non-phenolic compounds. This study was carried out to isolate and characterize laccase-producing fungi from environmental samples. Soil and decaying wood samples were collected from different locations within Ahmadu Bello University, Zaria Main Campus. Suspensions of the samples (1 g in 10 mL sterile distilled water) were serially diluted, inoculated onto Potato Dextrose Agar (PDA) containing 0.01% Chloramphenicol, and incubated for 7 days at 30°C. The fungal isolates were characterized macroscopically and microscopically with the aid of an atlas. The identified fungal isolates were screened for laccase production by inoculating onto PDA containing 0.02% Guaiacol, 1 mM ABTS (2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)), and 0.5% Tannic acid as indicator compounds and incubated at 25°C for 7 days. The laccase-producing isolates were confirmed molecularly by ITS rDNA sequence analysis using the FASTA algorithm with the Fungus database from the European Bioinformatics Institute (EBI). A total of 25 fungal species (11 from soil and 14 from decaying wood samples) were isolated. Two isolates from the soil origin identified as Curvularia lunata SSI7 (Accession No. QIE06317.1) and Fusarium clade VII SSI3 (Accession No. GQ505677) were found to produce laccase, where Curvularia lunata SSI7 was able to oxidize all the indicator compounds used for the screening. Fusarium clade VII SSI3 was able to oxidize only 0.5% Tannic acid. Laccase-producing Curvularia lunata and Fusarium clade VII were isolated from soil samples collected from ABU Zaria Main Campus.