The release of spent engine oil into the environment is a common problem that seriously impacts ecological balance of ecosystems. Engine oil is comprised of many petroleum hydrocarbons, in particular polycyclic aromatic hydrocarbons (PAHs). These hydrocarbons are of great attention because of their toxicity, carcinogenicity and mutagenic nature [1]. The removal and recovery of spilled or leaked engine oil can be achieved by physical and chemical means, but these approaches are usually costly, labor intensive, and cause adverse effects to contaminated sites [2,3]. Remediation of oil contamination by biological means or bioremediation then becomes a more effective approach. The ability of microorganisms to degrade hydrocarbons is involved in several factors, including catabolic enzyme activity, cell surface hydrophobicity and the nature of biosurfactant production [4]. Due to hydrophobicity property, bioremediation of hydrocarbons is usually

This work aimed to optimize carbon and nitrogen sources for the growth of Enterobacter cloacae B14 and its biosurfactant (BS) production via One-Variable-At-a-Time (OVAT) method. The BS stability under a range of pH and temperatures was assessed. Antimicrobial activity against Gram-positive and Gram-negative pathogens was determined by the agar well diffusion method. The results showed that the optimum carbon and nitrogen sources for BS production were maltose and yeast extract, respectively, with a maximum BS yield of (39.8 ± 5.2) mg BS/g biomass. The highest emulsification activity (E24) was 79%, which is significantly higher than in the previous studies. We found that B14 BS can withstand a wide range of pH values from 2 to10. It could also function under a range of temperatures from 30–37°C. Thin Layer Chromatography (TLC) and Fourier Transform Infrared Spectrometry (FTIR) analysis confirmed that B14 BS is a glycolipid-like compound, which is rarely found in Enterobacter spp. Cell-free broth showed inhibition against various pathogens, preferable to Gram-positive ones. It had better antimicrobial activity against Bacillus subtilis than a commonly-used antibiotic, tetracycline. Furthermore, B14 broth could inhibit the growth of a tetracycline-resistant Serratia marcescens. Our results showed promising B14 BS applications not only for bioremediation but also for the production of antimicrobial products.