Are Diamonds Forever? Biodegradation of Diamondoid Naphthenic Acids by Microbial Consortia

Abstract

Are Diamonds Forever? Biodegradation of Diamondoid Naphthenic Acids by Microbial Consortia

Oil sand deposits constitute more than half of global oil reserves. During surface oil-sand processing, vast quantities of oil sands process-affected waters (OSPW) are generated that contain naphthenic acids (NAs). NAs are recalcitrant and highly toxic; and thus the remediation of NAs in OSPW is of great environmental concern. Recently, diamondoid NAs were characterised in OSPW but there is currently a lack of information on their potential for biodegradation. This study aimed to investigate the efficacy of microbial consortia isolated from OSPW to degrade the diamondoid NAs, adamantane-1-carboxylic acid (A1CA) and 3-ethyl-adamantane carboxylic acid (3EA) under aerobic conditions.

Gas chromatography-mass spectrometry analysis showed that the microbial communities obtained from OSPW samples degraded A1CA and 3EA by 71% and 50% respectively after 33 days, resulting in a 50% reduction in toxicity as determined by the Microtox® assay. Pyrosequencing analysis based on the bacterial 16S rRNA gene demonstrated significant shifts in community composition during biodegradation. Dominant bacteria at day 33 included Pseudomonas, Hydrogenophaga, Bacillus, Acidovorax, Flavobacterium and Methylobacterium spp. These data suggest that diverse communities are involved in the degradation of both A1CA and 3EA. This will enable more cost-effective bioremediation strategies to be developed for removing recalcitrant NAs from OSPW.