Abstract
Biosorbent materials are effective in the removal of spilled oil from water, but their effect on hydrocarbonoclastic bacteria is not known. Here, we show that corksorb, a cork-based biosorbent, enhances growth and alkane degradation by Rhodococcus opacus B4 (Ro) and Alcanivorax borkumensis SK2 (Ab). Ro and Ab degraded 96 ± 1% and 72 ± 2%, respectively, of a mixture of n-alkanes (2 g L–1) in the presence of corksorb. These values represent an increase of 6 and 24%, respectively, relative to the assays without corksorb. The biosorbent also increased the growth of Ab by 51%. However, no significant changes were detected in the expression of genes involved in alkane uptake and degradation in the presence of corksorb relative to the control without the biosorbent. Nevertheless, transcriptomics analysis revealed an increased expression of rRNA and tRNA coding genes, which confirms the higher metabolic activity of Ab in the presence of corksorb. The effect of corksorb is not related to the release of soluble stimulating compounds, but rather to the presence of the biosorbent, which was shown to be essential. Indeed, scanning electron microscopy images and downregulation of pili formation coding genes, which are involved in cell mobility, suggest that cell attachment on corksorb is a determinant for the improved activity. Furthermore, the existence of native alkane-degrading bacteria in corksorb was revealed, which may assist in situ bioremediation. Hence, the use of corksorb in marine oil spills may induce a combined effect of sorption and stimulated biodegradation, with high potential for enhancing in situ bioremediation processes.
Highlights
Global oil demand averaged 108 barrels per day in 2019 (U.S EIA (Energy Information Administration), 2020), entailing intensive exploitation of petroleum resources and significant environmental risks
Considering the unique chemical composition, structure, and properties of corksorb (Pintor et al, 2012, 2013), we hypothesize that this biosorbent may have the potential to enhance the growth and hydrocarbon degradation by hydrocarbonoclastic bacteria, which was studied in this work
Alkanes were chosen as model compounds, since they are the main components of crude oil and their biodegradation has an important impact on oil removal and environmental cleanup (Head et al, 2006)
Summary
Global oil demand averaged 108 barrels per day in 2019 (U.S EIA (Energy Information Administration), 2020), entailing intensive exploitation of petroleum resources and significant environmental risks. The genus Rhodococcus is one of the most versatile concerning hydrocarbon degradation, being able to metabolize different types of hydrocarbons – from alkanes with C6–C36 (Wentzel et al, 2007) to complex polycyclic aromatic compounds present in gasoline, diesel, engine, and crude oil (Koma et al, 2003; Binazadeh et al, 2009; Song et al, 2011; Auffret et al, 2015) They can be found in different natural environments, including marine sediments and water (Sharma and Pant, 2000; Heald et al, 2001; Peng et al, 2008). The presence of native bacteria in corksorb, capable of growing with alkanes, was investigated
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