Evaluation of algal phytodegradation of petroleum naphthenic acids

Abstract

The algal phytodegradation of a model naphthenic acid (4-methylcyclohexaneacetic acid) and an oilsands mixture of naphthenic acids (NAs) were evaluated in support of studies to remediate recalcitrant NAs in soils and water. The algae investigated included blue-green algae (Oscillatoria sp.; Aphanizomenon sp.; Anbaena sp.) green algae (Selenastrum sp.; Nannochloris sp.; Ankistrodesmus sp.; Scenedesmus sp.; Haematococcus sp.; Chlorella sp.) and diatoms (Naviculla (1), Naviculla (2) and Nitzschia sp.). Both the cis- and trans-isomers of the model NA were completely uptaken and presumed phytodegraded by the diatom algae Naviculla (2) sp. at a concentration of ∼5.5 mg/L within a period of 14 days. However, there was no evidence for the phytodegradation of the petroleum oilsands naphthenic acids mixtures, except for possibly experiments utilizing the green algae, Selenastrum sp. The differences in the phytodegradation of the model NA by the diatoms appears to be linked to differences in transport mechanisms by the algae along with differences in the concentration and structure of the respective naphthenic acids.

Keywords:

• Phytodegradation
• biotransformation
• metabolism
• diatoms
• naphthenic acid

Notes

^a The labels “1” in the third column refer to the order of the experiments (i.e., “1” refers to the first experiment) using the cis- and trans-isomers of 4-MCHAA. Control samples are denoted by C1 – C4 in Figure 2, Figure 3, Figure 4, Figure 5, Figure 6.