CFD and experimental microfluidic study of the interaction between a natural compound nanoemulsion and E. coli bacterium considering reaction-diffusion-convection model

Abstract

Essential oils have recently emerged as potent natural antibacterial agents that are effective against pathogenic bacteria. The antibacterial efficacy of a stabilized nanoemulsion of carvacrol (with a mean droplet size of 123.51 nm ± 4.2 nm) on a Gram-negative Escherichia coli (E. coli ATCC 25922) was experimentally and numerically studied utilizing a continuous-flow microfluidic system. The morphology of the destroyed bacteria was examined visually and, bacteria lysis was confirmed by measuring the release of cellular contents. After establishing the antibacterial capability kinetics of the carvacrol nanoemulsions, the acquired data from the time killing assay was used to characterize the E. coli lysis. Moreover, a computational fluid dynamics (CFD) model was implemented to evaluate the influence of altering key parameters such as the Reynolds number, flow rate ratio and inlet carvacrol concentration on the unlysed bacteria percentage at the outlet (Y1) and the mass flow rate (μg/s) of the lysed bacteria at the outlet (Y2). The maximum lysis reaction rate observed in the device was 0.96s-1 corresponding to an inlet carvacrol nanoemulsion concentration of 160μg/mL. The reaction rate (r) was established based on the carvacrol concentration (Aμg/mL) as r=-0.149A0.373. The results obtained from numerical simulations indicated that the Reynolds number causes the most changes in the average value of Y1, while carvacrol concentration impacted most on the average value of Y2 response. The findings presented in this article provide insight into the probable kinetics of carvacrol nanoemulsion antibacterial activity in the microfluidics system.