Evaluation of conventional and response surface level optimisation of n-dodecane (n-C12) mineralisation by psychrotolerant strains isolated from pristine soil at Southern Victoria Island, Antarctica

Abstract

BackgroundBiodegradation of hydrocarbons in Antarctic soil has been reported to be achieved through the utilisation of indigenous cold-adapted microorganisms. Although numerous bacteria isolated from hydrocarbon-contaminated sites in Antarctica were able to demonstrate promising outcomes in utilising hydrocarbon components as their energy source, reports on the utilisation of hydrocarbons by strains isolated from pristine Antarctic soil are scarce. In the present work, two psychrotolerant strains isolated from Antarctic pristine soil with the competency to utilise diesel fuel as the sole carbon source were identified and optimised through conventional and response surface method.ResultsTwo potent hydrocarbon-degraders (ADL15 and ADL36) were identified via partial 16S rRNA gene sequence analysis, and revealed to be closely related to the genus Pseudomonas and Rhodococcus sp., respectively. Factors affecting diesel degradation such as temperature, hydrocarbon concentration, pH and salt tolerance were studied. Although strain ADL36 was able to withstand a higher concentration of diesel than strain ADL15, both strains showed similar optimal condition for the cell’s growth at pH 7.0 and 1.0% (w/v) NaCl at the conventional ‘one-factor-at-a-time’ level. Both strains were observed to be psychrotrophs with optimal temperatures of 20 °C. Qualitative and quantitative analysis were performed with a gas chromatograph equipped with a flame ionisation detector to measure the reduction of n-alkane components in diesel. In the pre-screening medium, strain ADL36 showed 83.75% of n-dodecane mineralisation while the reduction of n-dodecane by strain ADL15 was merely at 22.39%. The optimised condition for n-dodecane mineralisation predicted through response surface methodology enhanced the reduction of n-dodecane to 99.89 and 38.32% for strain ADL36 and strain ADL15, respectively.ConclusionsStrain ADL36 proves to be a better candidate for bioaugmentation operations on sites contaminated with aliphatic hydrocarbons especially in the Antarctic and other cold regions. The results obtained throughout strongly supports the use of RSM for medium optimisation.

Production of Lipopeptide Biosurfactant by a Hydrocarbon-Degrading Antarctic Rhodococcus

“…Bacteria from the genus Rhodococcus are considered as naturally ubiquitous in the Antarctic environment due to their frequent occurrence and dominance in both pristine [ 10 ] and anthropogenic-polluted ecosystems [ 4 ]. The excellent ecological properties of Rhodococcus spp.…”

Comparison of Petroleum Hydrocarbons Degradation by Klebsiella pneumoniae and Pseudomonas aeruginosa

“…This difference was also reported for two bacterial strains (Pseudomonas (22.39-38.32%) and Rhodococcus sp. (87.35-99.89%)) in the degradation of diesel and its component n-alkane [66]. Additionally, this difference was found for extreme halophilic bacterial strains: one strain could degrade up to 47% of crude oil while another degraded 13% [67].…”

“…For example, the Dietzia strain DQ12-45-1b was reported to utilize a wide range of n-alkanes (C 6 -C 40 ) and aromatic compounds of crude oil as a sole carbon source while other strains only use some of these compounds (≤C 25 ) [71]. Similarly, Habib et al [66] reported that the bacterial strain ADL15 tended to degrade shorter n-alkanes (n-C 10 , n-C 11 , n-C 12 ) more effectively than the middle-chain n-alkanes, while the other bacterial strain, ADL36, could degrade most of the recognizable n-alkanes significantly. Therefore, we hypothesized that the difference in diesel degradation between the two strains was partly due to the fact that they had different capacities to utilize diesel constituents.…”

Biodegradation of diesel oil by cold-adapted bacterial strains of Arthrobacter spp. from Antarctica

“…Much less growth was observed at pH values of 6.0 and 8.0, demonstrating that both bacterial strains are pH sensitive. Several studies have reported optimal growth in diesel-degrading bacteria at near-neutral pH (Habib et al 2018).…”

“…The use of microbes capable of degrading hydrocarbons as well as of producing biosurfactants can speed up the bioremediation of hydrocarbon-polluted sites. The utilization of hydrocarbons by bacteria has been reported to depend strongly on environmental variables, including temperature, pH, salinity and nitrogen sources (Habib et al 2018). Thus, these environmental variables are important factors affecting the efficiency of diesel biodegradation.…”