Crude biosurfactant production and heterologous expression of rhamnolipid biosynthesis genes of Pseudomonas aeruginosa UA isolated from oil contaminated soil

Abstract

Biosurfactants, particularly rhamnolipids produced by Pseudomonas aeruginosa, have been increasingly used in industries because of their multifunctional properties, including emulsification, foaming, and antimicrobial activities. Despite its excellent characteristics, the use of these rhamnolipids is still limited due to the pathogenicity of P. aeruginosa. This study investigates the potential production of biosurfactant by P. aeruginosa strain UA isolated from oil-contaminated soil in Indonesia while exploring the heterologous expression of rhamnolipid biosynthesis genes in Escherichia coli BL21(DE3) to overcome safety concerns. Crude biosurfactant production was confirmed through microplate, oil spreading, and drop collapse assays, with significant surface tension reduction and emulsification activity observed. Glycerol as a carbon source enhanced biosurfactant production, yielding emulsification activity comparable to the synthetic surfactant Tween-80. The much safer microbial host E. coli BL21(DE3) has successfully cloned and expressed the rhamnolipid biosynthesis genes (rhlA, rhlB, and rhlC). The results presented in this study confirm the biosurfactant production with recombinant system from P. aeruginosa strain UA. The limitations of industrial applications and future directions were also discussed for optimization and scalability.