Abstract
The antifungal activity of Lactobacillus pentosus ŁOCK 0979 depends both on the culture medium and on the fungal species. In the control medium, the strain exhibited limited antagonistic activity against indicator food-borne molds and yeasts. However, the supplementation of the bacterial culture medium with polyols (erythritol, lactitol, maltitol, mannitol, sorbitol, xylitol) or their galactosyl derivatives (gal-erythritol, gal-sorbitol, gal-xylitol) enhanced the antifungal properties of Lactobacillus pentosus ŁOCK 0979. Its metabolites were identified and quantified by enzymatic methods, HPLC, UHPLC-MS coupled with QuEChERS, and GC-MS. The presence of polyols and gal-polyols significantly affected the acid metabolite profile of the bacterial culture supernatant. In addition, lactitol and mannitol were used by bacteria as alternative carbon sources. A number of compounds with potential antifungal properties were identified, such as phenyllactic acid, hydroxyphenyllactic acid, and benzoic acid. Lactobacillus bacteria cultivated with mannitol synthesized hydroxy-fatty acids, including 2-hydroxy-4-methylpentanoic acid, a well-described antifungal agent. Scanning electron microscopy (SEM) and light microscopy confirmed a strong antifungal effect of L. pentosus ŁOCK 0979.
Highlights
Filamentous fungi and yeasts are present in almost all types of ecosystems due to their high adaptation ability and low nutritional requirements
The antagonistic activity of L. pentosus ŁOCK 0979 against the tested yeasts was weak, but its anticandidal properties were enhanced in the presence of galactosyl-polyols, and especially gal-erythritol
The growth of A. brassicicola and A. niger was inhibited by L. pentosus ŁOCK 0979 only if the bacterial culture medium was supplemented with polyols or gal-polyols
Summary
Filamentous fungi and yeasts are present in almost all types of ecosystems due to their high adaptation ability and low nutritional requirements. Of particular application interest are lactobacilli, which convert carbohydrates into lactic and acetic acids (primary metabolites), as well as a range of secondary metabolites, such as carbon dioxide, ethanol, hydrogen peroxide, fatty acids, acetoin, diacetyl, cyclic dipeptides, bacteriocins, and bacteriocin-like inhibitory substances [3]. Since these metabolites exhibit only weak antifungal properties, many research teams are seeking Lactobacillus strains with a higher natural ability to inhibit fungal and yeast growth [4, 9, 14, 15, 26]. Ryu et al [26] reported that Lactobacillus plantarum HD1 synthesizes 5-oxododecanoic acid (MW 214), 3-hydroxydecanoic acid (MW 188), and 3-hydroxy-5dodecenoic acid (MW 214), which are considered antifungal
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