The present invention relates to a bacterium of the species Lactobacillus fermentum having the ability to inhibit the growth of the fungus Penicillium solitum deposited under the accession No.: DSM32093 or the growth of the fungus Penicillium brevicompactum deposited under the accession No.: DSM32094 by at least 50%. The inhibitory activity can be determined in an assay comprising: (1) preparing a fermented milk product by: (a) inoculating a milk with the Lactobacillus fermentum in a concentration of at least 10