Antimicrobial spectrum and target site of d-3-phenyllactic acid

Geotrichum candidum excretes d-3-phenyllactic acid, which inhibits the growth of Listeria monocytogenes. It was found to inhibit a range of Gram-positive bacteria found in humans and foodstuffs, such as Staphylococcus aureus and Enterococcuss faecalis, and Gram-negative bacteria from humans, such as Providencia stuartii and Klebsiella oxytoca. Scanning electron microscope studies on the effect of d-3-phenyllactic acid on L. monocytogenes showed that it caused changes in bacterial behavior and structure. The bacteria formed aggregates and secreted polysaccharides; their cell walls lost their rigidity, causing the cells to swell. Finally the bacteria broke down completely and the cells disintegrate.