Investigating the Effects of Bis (2-ethylhexyl) Phthalate (DEHP) on the Growth of Escherichia coli strain BL21

SUMMARY Phthalates (also known as phthalate esters) are organic chemicals used as plasticizers in a wide range of food packaging, containers, and other household plastic objects. Humans are exposed to phthalates through the air and by ingestion. Phthalate exposure has been shown to induce changes to the microbiome, causing shifts in the resident microbiota in a dose-dependent manner. One phthalate in particular, Bis 2-ethylhexyl) phthalate (DEHP), is known to be present at high concentrations in Canadian food packaging. Previous research has found that DEHP has biphasic effects on the growth of Escherichia coli. To further investigate the effect DEHP may have on the growth of E. coli relevant to the human gut, our research set out to determine the effects of dose-dependent exposure on E. coli BL21. To do this, minimum inhibitory concentration (MIC) and growth curve assays were conducted. In the MIC assay, growth was observed at all concentrations, with a limited inhibitory effect on E. coli growth. However, phase separation between the DEHP solution and E. coli culture media made it difficult to determine whether growth inhibition was due to the DEHP or to inadequate aeration of the growing culture. The addition of ethanol reduced the phase separation between DEHP and E. coli culture media. However, subsequent growth curves showed conflicting results suggesting that the addition of ethanol may be the reason for reduced growth rate.