Bioprotective lactobacilli in Crescenza and Gouda cheese models to inhibit fungal spoilage.

Bioprotective cultures are applied to control the fungal spoilage of fermented dairy products but only few studies evaluated their efficacy in cheese. To evaluate growth and antifungal activity of bioprotective lactobacilli, cultures were used singly and combined adjunct cultures for laboratory-scale Crescenza cheese, a fresh cheese, and for pilot-scale Gouda cheese, respectively. Growth of the bioprotective cultures was characterized by surface plating, strain-specific qPCR and nanopore sequencing of full-length 16S rRNA genes. Analysis of Crescenza cheese by viable plate counts documented growth over 14 d of storage. In Gouda cheese, strain-specific qPCR demonstrated the growth of the lactobacilli during the first 45 d of ripening. Metagenomic sequencing demonstrated that the microbial community of Gouda cheeses was dominated by the starter and adjunct cultures with the relative abundance of other bacteria accounting for less than 0.5%. Adjunct cultures inhibited Penicillium caseifulvum and Penicillium roqueforti in Crescenza cheese; Lacticaseibacillus rhamnosus FUA3185 and Lacticaseibacillus paracasei FUA3413 extended the mold-free days almost 1.5-fold. Growth of yeasts was not inhibited. In Gouda cheese, Lactiplantibacillus plantarum FUA3183 and FUA3247 reduced the growth of Debaryomyces hansenii FUA4064 by 1.5 log and extended the mold-free shelf life for 3 d in 45 d-ripened cheese. Longer ripening time decreased the antifungal activity and the culture was no longer active towards yeasts. The abundance of Mn2+ in the curds of Crescenza cheese (0.2–0.4 mg kg−1 FW) was not altered by bioprotective cultures. The antifungal effect of Lct. rhamnosus , Lct. paracasei and Lactiplantibacillus plantarum thus depends on the type of cheese. • Antifungal lactobacilli inhibited mycelial molds but not yeasts in fresh cheese. • Antifungal lactobacilli only weakly inhibited mycelial molds in Gouda. • Lct. rhamnosus, Lct. paracasei and Lp. plantarum were antifungal in both models. • Ff. milii was effective only in fresh cheese. • Starter and adjunct cultures dominated cheese microbiota throughout 90 d of ripening. [ABSTRACT FROM AUTHOR]