The Interactions among Isolates of Lactiplantibacillus plantarum and Dairy Yeast Contaminants: Towards Biocontrol Applications

Abstract

Yeast diversity in the cheese manufacturing process and in the cheeses themselves includes indispensable species for the production of specific cheeses and undesired species that cause cheese defects and spoilage. The control of yeast contaminants is problematic due to limitations in sanitation methods and chemicals used in the food industry. The utilisation of lactic acid bacteria and their antifungal products is intensively studied. Lactiplantibacillus plantarum is one of the most frequently studied species producing a wide spectrum of bioactive by-products. In the present study, twenty strains of L. plantarum from four sources were tested against 25 species of yeast isolated from cheeses, brines, and dairy environments. The functional traits of L. plantarum strains, such as the presence of class 2a bacteriocin and chitinase genes and in vitro production of organic acids, were evaluated. The extracellular production of bioactive peptides and proteins was tested using proteomic methods. Antifungal activity against yeast was screened using in vitro tests. Testing of antifungal activity on artificial media and reconstituted milk showed significant variability within the strains of L. plantarum and its group of origin. Strains from sourdoughs (CCDM 3018, K19-3) and raw cheese (L12, L24, L32) strongly inhibited the highest number of yeast strains on medium with reconstituted milk. These strains showed a consistent spectrum of genes belonging to class 2a bacteriocins, the gene of chitinase and its extracellular product 9 LACO Chitin-binding protein. Strain CCDM 3018 with the spectrum of class 2a bacteriocin gene, chitinase and significant production of lactic acid in all media performed significant antifungal effects in artificial and reconstituted milk-based media.

Characterisation of Wild Strains of Lactic Acid Bacteria Isolated from Legumes and Their Biocontrol Potential against Fusarium spp.

“…Therefore, it remains unclear whether the strain variability in clades can influence the production of antifungal metabolites with target activity, especially when isolates are from similar competitive environments. Our recent study [15] confirmed that strains from microbiologically rich environments, such as silages, have considerable inhibitory effects on a spectrum of yeasts.…”

“…The extracellular proteins and peptides were isolated and visualised as described by [15], with minor changes. The Amicon ProAffinity Concentrator 30.000 NMWL (Merck Millipore Ltd., Tullagreen, Ireland) was used according to the instruction manual to concentrate the extracellular proteins and peptides in the CFS.…”

“…The amounts of lactic and acetic acid were the same in both media, except for isolate E (L. paracasei). Strains CCDM 191 and 196, whose lactic and acetic acid production was recently reported [15], were used as positive controls. Phenylated forms of lactic acid and other organic acids are most effective in terms of the antifungal activity of lactobacilli [47,48].…”

“…Studies on plant-associated LAB have confirmed that LAB strains isolated from the same plants show genetic relatedness, similar carbohydrate utilisation, and stress adaptability [13,14]. LAB strains from competing sources (silage and sourdough) showed a stronger antifungal effect than those from a uniform matrix [15,16].…”

“…The antifungal activity of LAB results from metabolites regulated by gene expression and is considered an intraspecific trait [17]. Short-chain organic acids, bacteriocins, chitinolytic enzymes, and volatile compounds are believed to be the metabolites that inhibit fungal growth and spore germination [15,18]. Lactiplantibacillus plantarum and other lactobacilli are the most intensively studied genera of LAB in relation to their antifungal activity against Fusarium spp.…”