Selection of sourdough lactobacilli with antifungal activity for use as biopreservatives in bakery products

Two hundred and sixteen LAB cultures from sourdoughs and dough for bread and panettone production were screened for in vitro antifungal properties against three indicator cultures ascribed to Aspergillus japonicus, Eurotium repens, and Penicillium roseopurpureum, isolated from bakery environment and moldy panettone. Nineteen preselected isolates were subjected to minimum inhibitory concentration determination against the indicator cultures. Sourdoughs prepared with the two most promising strains, identified as Lactobacillus rossiae LD108 and Lactobacillus paralimentarius PB127, were characterized. The sourdough extracts were subjected to HPLC analysis coupled with a microtiter plate bioassay against A. japonicus to identify the active fractions. MALDI-TOF MS analysis revealed the occurrence of a series of peptides corresponding to wheat α-gliadin proteolysis fragments in the active fraction from L. rossiae LD108 sourdough. The ability to prevent mold growth on bread was demonstrated for both strains, whereas L. rossiae LD108 also inhibited mold growth on panettone.