Antifungal activity of lactobacilli and its relationship with 3-phenyllactic acid production

• Thirteen LAB were tested for their ability to inhibit the growth of food spoilage molds.
• Tested molds were inhibited in different extent by the studied LAB.
• Phenyllactic acid (PLA) was not found in every one of cell-free supernatant (CFS) from LAB.
• The inhibition ability of CFS was affected by pH modification, but not by heating.
• PLA is not the only compound related with the antifungal activity.

In this study, 13 lactic acid bacteria (LAB) strains (including 5 Lactobacillus casei, 2 Lactobacillus rhamnosus, 2 Lactobacillus fermentum, 1 Lactobacillus acidophilus, 1 Lactobacillus plantarum, 1 Lactobacillus sakei, and 1 Lactobacillus reuteri species) were assessed for both their antifungal activity against four food spoilage molds (Colletotrichum gloeosporioides, Botrytis cinerea, Penicillium expansum, and Aspergillus flavus) and their capability to produce the novel antimicrobial compound 3-phenyllactic acid (PLA). Results demonstrated that all molds were sensitive to varying degrees to the cell-free supernatants (CFS) from LAB fermentations (p < 0.05), with growth inhibitions ranging from 2.65% to 66.82%. The inhibition ability of CFS was not affected by a heating treatment (121 °C, 20 min); however, it declined markedly when the pH of CFS was adjusted to 6.5. With the exception of L. plantarum NRRL B-4496 and L. acidophilus ATCC-4495, all other LAB strains produced PLA ranging from 0.021 to 0.275 mM. The high minimum inhibitory concentration for commercial PLA (3.01–36.10 mM) suggests that it cannot be considered the only compound related with the antifungal potential of studied LAB and that synergistic effects may exist among other metabolism products.