Probiotic Properties and Antioxidant Activity In Vitro of Lactic Acid Bacteria

Abstract

The properties of probiotics such as lactic acid bacteria (LAB) have been widely studied over the last decades. In the present study, four different LAB species, namely <i>Lactobacillus gasseri</i> ATCC 33323, <i>Lacticaseibacillus rhamnosus</i> GG ATCC 53103, <i>Levilactobacillus brevis</i> ATCC 8287, and <i>Lactiplantibacillus plantarum</i> ATCC 14917, were investigated in order to determine their ability to survive in the human gut. They were evaluated based on their tolerance to acids, resistance to simulated gastrointestinal conditions, antibiotic resistance, and the identification of genes encoding bacteriocin production. All four tested strains demonstrated high resistance to simulated gastric juice after 3 h, and the viable counts revealed declines in cell concentrations of less than 1 log cycle. <i>L. plantarum</i> showed the highest level of survival in the human gut, with counts of 7.09 log CFU/mL. For the species <i>L. rhamnosus</i> and <i>L. brevis</i>, the values were 6.97 and 6.52, respectively. <i>L. gasseri</i>, after 12 h, showed a 3.96 log cycle drop in viable counts. None of the evaluated strains inhibited resistance to ampicillin, gentamicin, kanamycin, streptomycin, erythromycin, clindamycin, tetracycline, or chloramphenicol. With regard to bacteriocin genes, the Pediocin PA gene was identified in <i>Lactiplantibacillus plantarum</i> ATCC 14917, <i>Lacticaseibacillus rhamnosus</i> GG ATCC 53103, and <i>Lactobacillus gasseri</i> ATCC 33323. The PlnEF gene was detected in <i>Lactiplantibacillus plantarum</i> ATCC 14917 and <i>Lacticaseibacillus rhamnosus</i> GG ATCC 53103. The Brevicin 174A and PlnA genes were not detected in any bacteria. Moreover, the potential antioxidant activity of LAB's metabolites was evaluated. At the same time, the possible antioxidant activity of metabolites of LAB was first tested using the free radical DDPH^• (a, a-Diphenyl-β-Picrylhydrazyl) and then evaluated with regard to their radical scavenging activity and inhibition against peroxyl radical induced DNA scission. All strains showed antioxidant activity; however, the best antioxidant activity was achieved by <i>L. brevis</i> (94.47%) and <i>L. gasseri</i> (91.29%) at 210 min. This study provides a comprehensive approach to the action of these LAB and their use in the food industry.