Purification and characterization of novel antifungal compounds from the sourdough Lactobacillus plantarum strain 21B

Sourdough lactic acid bacteria were selected for antifungal activity by a c onidial germination assay. The 10-fold-concentrated culture filtrate of Lac tobacillus plantarum 21B grown in wheat flour hydrolysate almost completely inhibited Eurotium repens IBT18000, Eurotium rubrum FTDC3228, Penicillium corylophilum IBT6978, Penicillium roqueforti IBT18687, Penicillium expansum IDM/FS2, Endomyces fibuliger IBT605 and IDM3812, Aspergillus niger FTDC322 7 and IDM1, Aspergillus flavus FTDC3226, Monilia sitophila IDM/FS5, and Fus arium graminearum IDM623. The nonconcentrated culture filtrate of L. planta rum 21B grown in whole wheat flour hydrolysate had similar inhibitory activ ity. The activity was fungicidal. Calcium propionate at 3 mg ml(-1) was not effective under the same assay conditions, while sodium benzoate caused in hibition similar to L. plantarum 21B. After extraction with ethyl acetate, preparative silica gel thin-layer chromatography, and chromatographic and s pectroscopic analyses, novel antifungal compounds such as phenyllactic and 4-hydroxyphenyllactic acids were identified in the culture filtrate of L. p lantarum 21B. Phenyllactic acid was contained at the highest concentration in the bacterial culture filtrate and had the highest activity. It inhibite d all the fungi tested at a concentration of 50 mg ml(-1) except for P. roq ueforti IBT18687 and P. corylophilum IBT6978 (inhibitory concentration, 166 mg ml(-1)). L. plantarum 20B, which showed high antimold activity, was als o selected. Preliminary studies showed that phenyllactic and 4-hydroxy-phen yllactic acids were also contained in the bacterial culture filtrate of str ain 20B, Growth of A. niger FTDC3227 occurred after 2 days in breads starte d with Saccharomyces cerevisiae 141 alone or with S. cerevisiae and Lactoba cillus brevis 1D, an unselected but acidifying lactic acid bacterium, while the onset of fungal growth was delayed for 7 days in bread started with S. cerevisiae and selected L. plantarum 21B.