Assessment of Biosurfactant Production and Petroleum Hydrocarbons Biodegradation Capability of Actinomycetes Isolated from Soils

Production of biosurfactants and emulsifiers by bacteria has been suggested to enhance the biodegradability of hydrocarbons (HCs) in complex matrices like crude oil and its refined products. Recent studies have focused on the capability of actinobacteria to biodegrade HCs because of their abundance in soils and high tolerance to recalcitrant chemicals. Here, actinomycetes isolated from pesticide-impacted agricultural soils were assessed for their biosurfactant production and complex HC biodegradation capabilities. Five actinomycetes (Lentzea albidocapillata, Actinomyces slackii, Actinomyces liubingyangii Rhodococcus erythropolis and Trueperella bernardiae) identified based on morphological, physiological, and 16S rRNA gene sequencing were assessed for biosurfactant production using four tests. The biodegradation capability was assayed in aviation fuel, petrol, kerosene, diesel and crude oil using the standard CO2 respirometry for 30 days. All isolates exhibited high emulsifying activity (35.71 - 65.12%) in all HCs but their ability to adhere to hydrophobic surfaces varied greatly (28.77-70.11%) with L. albidocapillata demonstrating the most significant hydrophobicity. With the exception of T. bernardiae, all actinomycetes' whole-cell suspensions and cell-free supernatants generated sizable biosurfactants that removed diesel film from water more effectively than crude oil. Biosurfactants produced by A. liubingyangii caused the greatest displacement of the oils. The complex HCs were mineralized to different extents, with the highest extent of mineralization by L. albidocapillata in petrol (53.40mgCO2/mL). The findings imply that the ability of these actinomycetes to adhere to hydrophobic matrices and produce biosurfactants with strong emulsifying activity makes them good candidates for bioremediation of complex HCs like crude oil and its refined products.