Microbial enhanced heavy oil recovery through biodegradation using fungal extracellular enzymes from Aspergillus spp.

Abstract

Background: The progressive depletion of light crude oils has led to increased focus on efficient exploitation of heavy oil reserves to meet energy demand. Microbial enhanced oil recovery makes a substantial contribution to the recovery of heavy oils; however, most methods use bacteria, with less attention paid to the potential of fungi. In this study, we investigated the efficiency of fungal extracellular enzymes in biotransformation and biodegradation of heavy oil fractions into light compounds and the feasibility of the use of such enzyme preparations in enhanced oil recovery. Results: Two fungal strains of Aspergillus spp., isolated from bitumen samples, showed good growth on plates of mineral salts medium with heavy oil as the sole carbon source. The fungal extracellular enzymes, with dehydrogenase and catechol 2,3-dioxygenase activities, exhibited the ability to biodegrade heavy oil. The biodegradation process was coupled with abundant production of gases, mainly CO 2 and H 2 . Gas chromatography analysis revealed a significant redistribution of n -alkanes in the heavy oil after treatment with fungal enzyme preparations, which resulted in an increase in individual n -alkanes. The viscosity of the heavy oil was decreased 66.33% by fungal enzymatic degradation. Conclusions: These results demonstrate the potential of fungal extracellular enzymes from Aspergillus spp. for applications in enhanced heavy oil recovery, including biotransformation of heavy to lighter crude oil and byproduct biogas formation.