Evaluation of hydrocarbon degrading potentials of cellulolytic edaphic borne fungi

Abstract

This study assessed the hydrocarbon degradative potentials of cellulolytic fungi cultured from top soil samples within Benin City, Edo State. Soil samples were collected from 3 sites; a farmland, a fallow plant covered land, and municipal dumpsite. Physicochemical parameters of the soil samples were based on standard methods. Standard cultural and molecular techniques were used to isolate and identify fungi present in samples. Cellulolytic activity of fungal isolates was determined with Czapek-dox agar supplemented with 0.1% sodium carboxymethyl cellulose (CMC). Cellulolytic fungi were subsequently screened for the ability to utilize blended petroleum as sole carbon source. Further, two isolates having the highest optical density were used for growth profile study as axenic culture and in consortium. The growth profile study assessed pH, optical density, total petroleum hydrocarbon content and fungal dry mass. Results showed that the organic carbon value of the top soils ranged from 4.14 g/kg ± 0.55 to 8.56 g/kg ± 0.05. All collected soil samples were sandy, while total hydrocarbon content ranged from 0.38 g/kg ± 0.04 to 1.13 g/kg ± 0.01. The mean fungal counts were highest in dumpsite soils and ranged from 4.0 × 10³ cfu/g ± 1414 to 7.0 × 103 cfu/g ± 1003. Eight fungal isolates with cellulolytic properties were identified from the soil samples. Trichosporon asahii and Curvularia bothriochloae had highest (p < 0.05) OD when grown on blended petroleum and were used for growth profile studies. OD was highest (p < 0.05) in C. bothriochloae (0.372 ± 0.0005) relative to T. asahii and the consortium at 15 d. THC reduced significantly (p < 0.05) in both axenic cultures and the consortium after 15 days, while fungal biomass was highest (p < 0.05) in consortium relative to axenic cultures after 15 d. This study showed hydrocarbon degrading capabilities of cellulolytic fungi from different top soils.