Assessment of the Petroleum Oil Degradation Capacity of Indigenous Bacterial Species Isolated from Petroleum Oil-Contaminated Soil

Petroleum hydrocarbons are highly toxic to plants, animals, and humans and are carcinogenic effects to plants, animals, and humans. The present study is focused to enhance the degradation of petroleum hydrocarbons using potential indigenous bacterial isolates. Bacteria were isolated from different petroleum oil-contaminated sites and characterized. Bacterial growth was evaluated under different physico-chemical parameters. The petroleum hydrocarbon degradation potentiality was assessed using GC-MS analysis. Forty-nine bacterial isolates were screened; only three isolates (ALK-14, ALK-16, and ALK-23) have good potential to degrade petroleum hydrocarbons and were identified as Alcaligenes species ALK-14, Bacillus methylotrophicus ALK-16, and Enterobacter species ALK-23, respectively, on the basis of morphology, biochemical characterization, and 16S rRNA sequencing. Optimum growth of Alcaligenes species ALK-14, Bacillus methylotrophicus ALK-16, and Enterobacter species ALK-23 occurred at pH 7, 6, and 6, respectively. Petroleum oil concentration found suitable for growth of selected bacterial isolates Alcaligenes species ALK-14, Bacillus methylotrophicus ALK-16, and Enterobacter species ALK-23 were 4%, 8%, and 4% (v/v), respectively. Among different nitrogen sources, ammonium nitrate was found suitable source for the maximum growth of Alcaligenes species ALK-14, Bacillus methylotrophicus ALK-16 at the concentration of 0.15 and 0.2%, respectively, and sodium nitrate for Enterobacter species ALK-23 at the concentration of 0.2%. All bacterial isolates showed maximum growth at 30 degrees C temperature. Synergistic effect on the growth of bacterial isolates under favourable conditions increased up to 11-28%. GC-MS analysis indicated that the hydrocarbon compounds in the range of C-20-C-44 were present in petrol. Maximum hydrocarbon degradation by Alcaligenes species ALK-14, Bacillus methylotrophicus ALK-16, and Enterobacter species ALK-23 was 11.65%, 8.11%, and 5.59%, respectively. The degradation of docosane 11-decyl, hexatriacontane, and eicosane by Alcaligenes species ALK-14 was 100%, 60%, and 48.8%, respectively. The degradation of docosane 11-decyl by, Bacillus methylotrophicus ALK-16, was 80%. Degradation of hexatriacontane by Enterobacter species ALK-23 was 31%. Further understanding of the metabolic processes of these organisms on crude oil hydrocarbons degradation will increase possibilities to develop strategies for removing crude oil pollutants from oil-impacted environments. Article Highlights Bacterial isolates Alcaligenes species ALK-14 degraded docosane 11-decyl, hexatriacontane and eicosane by Alcaligenes species ALK-14 was 100%, 60% and 48.8 % respectively and the obtained degradation pattern was 11-decyl > hexatriacontane > eicosane. Under optimized conditions, the parameters have showed synergistic effect therefore bacterial growth was enhanced up to 11-28% which is directly proportional to the hydrocarbon degradation. Eighty percent degradation of docosane 11-decyl was achieved by Bacillus methylotrophicus ALK-16.