ZnO nanoparticle engineered Pseudomonas aeruginosa SOA1 towards enhanced Rhamnolipid production

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Rhamnolipids, the potential biosurfactants, have widespread applications in pharmaceutics, food, and agriculture fields. However, its low biosynthesis efficiency limits surfactant industrialization. In this study, different nanoparticles (NPs) were immobilized over Pseudomonas aeruginosa (SOA1) and targeted towards increased rhamnolipids production by increasing the secretion (key step of rhamnolipids biosynthesis). It was observed that, upon adding ZnO NPs (4.0 g/L), rhamnolipids titer increased 4.87 times (from 4.1 to 19.98 g/L) in the 10 L bioreactor. This is due to an increment in the expression of the gene (present in the rhamnolipids biosynthesis process) with the introduction of ZnO NPs to SOA1. Further, with ZnO NPs, few rhamnolipid biosynthesis genes (rhlA and rhlB) were significantly upregulated. In contrast, the rhamnose biosynthetic genes (rmlA, rmlC, and algC) were down regulated during the early and late exponential growth phases as studied in Quantitative real-time PCR. The biosurfactant generation is regulated by quorum-sensing genes, which exhibit a hierarchical expression profile. Specifically, in the early log phase (ZnO NPs cultivation), the last gene was elevated, but both pqsE and rhlI were stimulated in the late log phase. This experiment paves a new path toward improving the biosynthesis of microbial metabolites via. NPs engineering.