Hydrocarbon Degradation and Enzyme Activities of Aspergillus oryzae and Mucor irregularis Isolated from Nigerian Crude Oil-Polluted Sites

Abstract

Many free-living saprobic fungi are nature recruited organisms for the degradation of wastes, ranging from lignocellulose biomass to organic/inorganic chemicals, aided by their production of enzymes. In this study, fungal strains were isolated from contaminated crude-oil fields in Nigeria. The dominant fungi were selected from each site and identified as Aspergillus oryzae and Mucor irregularis based on morphological and molecular characterization, with site percentage incidences of 56.67% and 66.70%, respectively. Selected strains response/tolerance to complex hydrocarbon (used engine oil) was studied by growing them on Bushnell Haas (BH) mineral agar supplemented with the hydrocarbon at different concentrations, i.e., 5%, 10%, 15%, and 20%, with a control having dextrose. Hydrocarbon degradation potentials of these fungi were confirmed in BH broth culture filtrates pre-supplemented with 1% engine oil after 15 days of incubation using GC/MS. In addition, the presence of putative enzymes, laccase (Lac), manganese peroxidase (MnP), and lignin peroxidase (LiP) was confirmed in culture filtrates using appropriate substrates. The analyzed fungi grew in hydrocarbon supplemented medium with no other carbon source and exhibited 39.40% and 45.85% dose inhibition response (DIR) respectively at 20% hydrocarbon concentration. An enzyme activity test revealed that these two fungi produced more Lac than MnP and LiP. It was also observed through the GC/MS analyses that while A. oryzae acted on all hydrocarbon components in the used engine oil, M. irregularis only degraded the long-chain hydrocarbons and BTEX. This study confirms that A. oryzae and M. irregularis have the potential to be exploited in the bio-treatment and removal of hydrocarbons from polluted soils.

Optimization of Mycoremediation Potential of A Fungi: Aspergillus Ochraceus Strain

“…The high tolerance of fungi to these complex hydrocarbons is not due to their ability to degrade but to enzyme secretions that increase biodegradation. (Aemoloye et al 2017, Asemoloye et al 2020).…”

“…In accordance with this study, Kota et al (2014) showed that A. avus and A. versicolor were resistant to petroleum contamination within the range of 5-1%. Although it was found that A. oryzae and M. irregularis can tolerate varying concentrations of engine oil, their growth rate and degradation abilities differ (Asemoloye et al 2020). The removal of 3% petroleum concentration with Saccharomyces sp.…”

“…The fungal strains were inoculated on PDA (potato dextrose agar) (Merck) and incubation was performed at 30 ℃ in static condition for a week. Following the fungal cultures were suspended in 0.9% NaCl (pH 7.0) solution, and the spores were counted on a Thoma slide (Asemoloye et al 2020).…”

“…In this direction, the most promising approach to treating these areas is biological methods (Deshmukh et al 2016;Islam et al 2017). Microbial Enhanced Oil Recovery (MEOR) is a cost-effective and environmentally friendly technology as well as being biologically based (Zhang et al 2016; Asemoloye et al 2020). Microbial degradation is one of the most important and fundamental mechanisms in the bioremediation of petroleum hydrocarbons.…”

Genome-based engineering of ligninolytic enzymes in fungi

“…lignin degradation, including laccase (LCC), lignin peroxidase (LiP), manganese peroxidase (MnP), and versatile peroxidase (Vp). These enzymes are characterised by broad specificity in degradation/mineralization of different complex substrates such as wood, paper, animal feeds, pesticides, biofuels, and hydrocarbons [2][3][4][5][6]. The importance of LEs in biotechnological, industrial, and environmental applications-especially in the production of bioenergy or biomaterials, is worldwide recognized [7].…”