Fermentation optimization, performance evaluation and whole-genome analysis of the biosurfactant-producing...

A biosurfactant (BS)-producing strain, designated GM6, was isolated from high-salinity oily wastewater and identified as Enterobacter sp. The optimal fermentation conditions for strain GM6 were olive oil as the carbon source, ammonium chloride as the nitrogen source, at 27 °C, with 20 g/L NaCl, pH 7, and a 3 % inoculum based on single factor and orthogonal experiment. The BS produced by strain GM6 was found to exhibit excellent surface activity, with a critical micelle concentration of 150 mg/L and a surface tension of 30.91 mN/m. Moreover, it also showed remarkable chemical stability across a wide range of salinities (10-100 g/L), temperatures (50-100 °C), and pH values (2-12). Through TLC, FTIR, and GC-MS analyses, the BS was identified as phospholipid. Genome analyses indicated that several genes may be involved in the metabolism of olive oil by GM6 and contribute to the synthesis of phospholipid BS, such as CDS1/CDS2 and PGS1. This study provides a valuable microbial resource for the development of BS and its potential industrial applications in olive oil processing wastewater.