An innovative approach in the food industry is the use of lactic acid fermentation to preserve foods and modify their physico-chemical and microbiological properties, such as beetroot juice (BJ, with a high rate of bioactive compounds), fermented with selected probiotic bacteria. This process provides strong antioxidant properties, as well as many taste and health benefits.
Our study focused on spray-dried (sd) or freeze-dried (fd) powders prepared from unfermented (NF-PBJ) and fermented beetroot juice (F-PBJ) using the probiotic Lactobacillus plantarum 299v, with the addition of 20% oligofructose. The aim was to evaluate the antimicrobial potential of PBJs, in the concentration range 7.81-32000 µg/mL, against a broad spectrum of reference bacterial strains (Micrococcus luteus, Staphylococcus epidermidis, S. aureus, Bacillus subtilis, B. cereus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Proteus mirabilis, Acinetobacter baumannii, and Salmonella typhimurium) using the broth microdilution method on Mueller–Hinton broth medium.
For all PBJs, the minimum inhibitory (MICs) and minimum bactericidal concentrations (MBCs) were in the range of 2-16 µg/mL and 4->32 µg/mL, respectively. Based on the MBC/MIC ratio, PBJ showed bacteriostatic (e.g. against S. aureus, B. subtilis, B. cereus, M. luteus) or bactericidal (e.g. against E. coli, P. aeruginosa, K. pneumoniae, A. baumannii, Salmonella spp.) activity, depending on the microbial strain, the contribution of the fermentation process, and the drying technique.
These results highlight the antimicrobial potential of PBJs, including activity against the selected diarrhoeal pathogens tested (e.g. E. coli, Salmonella spp.). The resulting sd/fd-F/NF-PBJs offer desirable antimicrobial properties as well as an improved taste profile and a convenient food formulation with significant technological potential. This suggests a broad potential for the use of PBJs in the production of innovative functional foods, pharmaceuticals, cosmetics, or dietary supplements.