A microbial solution to oil sand pollution: Understanding the microbiomes, metabolic pathways and mechanisms involved in naphthenic acid (NA) biodegradation

Bituminous oil sands arise from the microbial oxidation of petroleum hydrocarbons over geological time, with one of the largest deposits found in northern Alberta, Canada. Associated with bitumen are mixtures of toxic and persistent organic acids, known as naphthenic acids (NAs). NAs can be found in various natural environments that are in contact with the bitumen, such as river and wetland sediments. However, NAs may also accumulate through anthropogenic activities that follow oil sand mining operations. During bitumen extraction, vast quantities of toxic oil sands process-affected water (OSPW), are generated that are stored in large oil sands tailings ponds (OSTPs), often for decades and cause serious impacts to the local environment. Bioremediation of NAs using microorganisms, has clear cost and environmental advantages, yet there is a critical lack of fundamental knowledge of the functional microbiome in these NA associated ecosystems. This chapter seeks to unravel the complex microbiomes present in natural and anthropogenic bitumen-rich environments, including the genes, enzymes and mechanisms involved in NA biodegradation.