Isolation and characterization of novel hydrocarbon-degrading bacteria from oil polluted soil near Nacharam, Hyderabad, India

Petroleum is a vital and strategic energy resource for boosting a country's GDP. Despite its high economic value, it is considered a primary factor in environmental deterioration. Bioremediation strategies employ indigenous microbial strains to propose an economical and sustainable alternative to conventional remediation practices. The current study investigates the isolation, identification, and characterization of five novel biosurfactant-producing and petroleum hydrocarbon-degrading bacterial species: Rhodococcus indonesiensis strain SARSHI1, Pseudomonas aeruginosa strain SARSHI2, Pseudomonas argentinensis strain SARSHI3, Acinetobacter baumannii strain SARSHI4, and Rhodococcus qingshengii strain SARSHI5. Molecular identification was determined via 16S rRNA sequencing, and their taxonomic identities were validated through biochemical assessments. Their partial sequences were deposited in NCBI with accession numbers: 'PV034287', 'OP597529', 'OP584476', 'OQ711779', and 'OQ711775' respectively. Amongst them, R. indonesiensis exhibited the highest biosurfactant and hydrocarbon-degrading potential with a critical micelle concentration of 70 mg/L, reduced surface tension of 27 mN/m, an emulsification index (E₂₄) of 85.34%, and hydrocarbon-degrading potency of up to 90%. Gravimetric analysis revealed up to 84% hydrocarbon degradation when supplemented with glycerol, and GC-MS analysis confirmed the selective degradation of n-alkanes (C18-C24). Structural studies employing NMR established the biosurfactant as a lipopeptide. Statistical optimization utilizing RSM - Box-Behnken design obtained the optimized conditions for enhanced biosurfactant and biodegradation activity. Microcosm studies further assessed SARSHI1's bioremediation potential under field-simulated treatments, achieving up to 95% degradation rates under the combined treatment of Bioaugmentation + Biostimulation + Biosurfactant (BA + BS + B), signifying the amplified bioavailability of hydrocarbons. Phytotoxicity tests confirmed the environmental impact of the bacterial strain. The results govern a robust framework for advancing microbial applications in environmental remediation and further support R. indonesiensis SARSHI1 for large-scale biotechnological paradigms.