Evaluation of anti-yeast metabolites produced by Lactobacillus strains and their potential application as bio-preservatives in traditional yogurt drink

Abstract

Consumer demand for minimal food processing and reduced use of chemical preservatives has sparked interest in the use of biological preservatives. This study aimed to assess the anti-yeast effects of Lactobacillus delbrueckii, Limosilactobacillus fermentum, and Lactiplantibacillus plantarum strains on Saccharomyces cerevisiae, Candida albicans, and Geotrichum candidum. The anti-yeast activity of lactic acid bacteria (LAB) cell-free supernatant (CFS) was evaluated using well diffusion agar, agar spot assay, and scanning electron microscopy (SEM). Heat treatment's impact on the inhibitory capacity of CFS was also examined. Ion chromatography measured the production of propionic acid, lactic acid, and acetic acid in the supernatant. Furthermore, a yogurt drink containing the L. fermentum strain was produced. L. fermentum exhibited the highest anti-yeast activity against G. candidum, with an inhibition halo diameter of 16.60 mm. SEM revealed morphological changes in S. cerevisiae, C. albicans, and G. candidum following treatment with L. fermentum CFS. The production rates of lactic, propionic, and acetic acids in the L. fermentum supernatant without heat treatment were 94885.78, 115233, and 5936.02 ppm, respectively. Examination of mold, yeast, and coliform counts in samples inoculated with L. fermentum during 14 days of storage indicated that the microbial population remained within acceptable limits compared to control.