Abstract
Petroleum hydrocarbons, notably diesel oil, are the main energy source for running amenities in the Antarctic region and are the major cause of pollution in this area. Diesel oil spills are one of the major challenges facing management of the Antarctic environment. Bioremediation using bacteria can be an effective and eco-friendly approach for their remediation. However, since the introduction of non-native organisms, including microorganisms, into the Antarctic or between the distinct biogeographical regions within the continent is not permitted under the Antarctic Treaty, it is crucial to discover native oil-degrading, psychrotolerant microorganisms that can be used in diesel bioremediation. The primary aim of the current study is to optimize the conditions for growth and diesel degradation activity of an Antarctic local bacterium, Arthrobacter sp. strain AQ5-05, using the Plackett-Burman approach and response surface method (RSM) via a central composite design (CCD) approach. Based on this approach, temperature, pH, and salinity were calculated to be optimum at 16.30 °C, pH 7.67 and 1.12% (w/v), respectively. A second order polynomial regression model very accurately represented the experimental figures’ interpretation. These optimized environmental conditions increased diesel degradation from 34.5% (at 10 °C, pH 7.00 and 1.00% (w/v) salinity) to 56.4%. Further investigation of the kinetics of diesel reduction by strain AQ5-05 revealed that the Teissier model had the lowest RMSE and AICC values. The calculated values for the Teissier constants of maximal growth rate, half-saturation rate constant for the maximal growth, and half inhibition constants (μmax, Ks, and Ki), were 0.999 h−1, 1.971% (v/v) and 1.764% (v/v), respectively. The data obtained therefore confirmed the potential application of this cold-tolerant strain in the bioremediation of diesel-contaminated Antarctic soils at low temperature.
Highlights
Human activity in Antarctica, the establishment and operation of research stations and various forms of hydrocarbon-powered transport, brings with it the threat of hydrocarbon spills, notably diesel oil leaking from storage tanks, and spills in the transportation of fuel as well as the refueling of generators and vehicles [1,2,3]
The common widely used oil in Antarctica, is made up of aliphatic and aromatic hydrocarbons that are persistent if released into the environment [5,6], due to the frequently low temperatures, nutrient inaccessibility and arid conditions, which inhibit the rate of bacterial processes and abiotic degradation [7,8]
Species of Bacillus, Enterobacter, Pseudomonas, Rhodococcus, and Arthrobacter have been described as being capable of diesel degradation [30,52,53] and there are reports of petroleum hydrocarbons degrading Arthrobacter sp. strains (n-alkanes and phenol) at lower temperature, similar to the results obtained in this study
Summary
Human activity in Antarctica, the establishment and operation of research stations and various forms of hydrocarbon-powered transport, brings with it the threat of hydrocarbon spills, notably diesel oil leaking from storage tanks, and spills in the transportation of fuel as well as the refueling of generators and vehicles [1,2,3]. Diesel oil spills are the main cause of pollution caused directly by human activities on the Antarctic continent and potentially create serious impacts on native ecosystems [4]. The common widely used oil in Antarctica, is made up of aliphatic and aromatic hydrocarbons that are persistent if released into the environment [5,6], due to the frequently low temperatures, nutrient inaccessibility and arid conditions, which inhibit the rate of bacterial processes and abiotic degradation [7,8]. A number of researchers have demonstrated the competence of local microorganisms to degrade petroleum hydrocarbon pollutants in the unfriendly environmental conditions of Antarctica [7,15,16,17]
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