In vitro and in situ screening of lactic acid bacteria and propionibacteria antifungal activities against bakery product spoilage molds

In the agri-food context, bioprotective cultures represent an interesting alternative to chemical preservatives. The aim of this study was to evaluate the in vitro and in situ antifungal activity of lactic acid bacteria (LAB) and propionibacteria against bakery product spoilage fungi. Firstly, the biodiversity of fungal contaminant in pound cakes and milk bread rolls, as well as the resistance to chemical preservatives of representative isolates (n = 21), were studied. Aspergillus and Eurotium species were the most dominant spoilage fungi and the most resistant towards the tested chemical preservatives. They were followed by Penicillium, Cladosporium and Wallemia spp. Secondly, an in vitro screening showed that the most active isolates against selected fungal targets belonged to the Leuconostoc spp., Lactobacillus reuteri and Lactobacillus buchneri groups among the 270 tested LAB, as well as to the Propionibacterium freudenreichi and Propionibacterium acidipropionici species for the 50 tested propionibacteria. Finally, in situ tests showed that cultures of isolates belonging to the Leuconostoc citreum, Lactobacillus sakei, Lactobacillus plantarum, Lactobacillus spicheri, L. reuteri and Lactobacillus brevis species could delay one or several target fungal growths after bakery product surface spraying. Moreover, different strain cultures led to delayed fungal growths after incorporation in milk bread rolls preparation. The combination of in vitro and in situ approaches allowed for the identification of bacteria exhibiting antifungal activity, providing future prospects for use as bioprotective cultures in bakery products.