The acid tolerance response and pH adaptation of Enterococcus faecalis in extract of lime Citrus aurantiifolia from Aceh Indonesia

<ns4:p><ns4:bold>Background:</ns4:bold> The objective of the present study was to evaluate the acid tolerance response and pH adaptation when<ns4:italic>Enterococcus</ns4:italic><ns4:italic>faecalis</ns4:italic>interacted with extract of lime (<ns4:italic>Citrus aurant</ns4:italic><ns4:italic>iifolia</ns4:italic>).</ns4:p><ns4:p><ns4:bold>Methods</ns4:bold><ns4:bold>:</ns4:bold>We used<ns4:italic>E. faecalis</ns4:italic>ATCC 29212 and lime extract from Aceh, Indonesia. The microbe was analyzed for its pH adaptation, acid tolerance response, and adhesion assay using a light microscope with a magnification of x1000. Further, statistical tests were performed to analyze both correlation and significance of the acid tolerance and pH adaptation as well as the interaction activity.</ns4:p><ns4:p><ns4:bold>Results</ns4:bold><ns4:bold>:</ns4:bold><ns4:italic>E. faecalis</ns4:italic>was able to adapt to a very acidic environment (pH 2.9), which was characterized by an increase in its pH (reaching 4.2) at all concentrations of the lime extract (p < 0.05).<ns4:italic>E. faecalis</ns4:italic>was also able to provide acid tolerance response to lime extract based on spectrophotometric data (595 nm) (p < 0.05). Also, the interaction activity of<ns4:italic>E. faecalis</ns4:italic>in different concentrations of lime extract was relatively stable within 6 up to 12 hours (p < 0.05), but it became unstable within 24–72 hours (p > 0.05) based on the mass profiles of its interaction activity.</ns4:p><ns4:p><ns4:bold>Conclusions</ns4:bold><ns4:bold>:</ns4:bold><ns4:italic>E. faecalis</ns4:italic>can adapt to acidic environments (pH 2.9–4.2); it is also able to tolerate acid generated by<ns4:italic>Citrus auranti</ns4:italic><ns4:italic>ifolia</ns4:italic>extract, revealing a stable interaction in the first 6–12 hours.</ns4:p>