Prospecting and characterization of potential probiotic Lactobacillus species from animal gut and food sources

Background: There has been a growing interest among researchers in identifying highly functional probiotic Lactobacillus species from plant and animal sources in recent times. This study aims to prospect and characterize Lactobacillus species with probiotic potential from animal gut, fruit, and vegetable sources. Method: Lactobacillus species were isolated from samples using selective enrichment techniques. Colony morphology, catalase testing, and Gram staining were used for the preliminary identification of the presumptive Lactobacillus strains. Their identities were subsequently confirmed by 16S rRNA gene sequencing and BLAST analysis. The identified Lactobacillus strains were subjected to in vitro characterization to assess their probiotic properties. Results: Ten Lactobacillus species isolates demonstrated high acid tolerance, with survivability exceeding 50% at pH 2.5 and 3.0. Their survival rates ranged from 62.05% to 97.42% and from 81.12% to 99.31% in the presence of 0.5% and 0.3% bile salt concentrations, respectively. All the isolates exhibited varying capacities to reduce cholesterol (13.06% –57.64%) and demonstrated antioxidant activity ranging from 6.81% to 24.45%. Only one isolate (Mcxc) lacked bile salt hydrolase activity, and 33.33% of the isolates did not produce any exopolysaccharides. The auto-aggregation abilities ranged from 18% to 52% after 4 h of incubation, while cell surface hydrophobicity ranged from 0.00% to 84.68%. None of the isolates exhibited haemolytic or DNase activity. The degree of adhesion to Caco-2 cells ranged from 2.6% to 15.29%. All isolates were susceptible to erythromycin, chloramphenicol, ampicillin, and penicillin G. Notably, only four Lactobacillus isolates exhibited inhibitory activity against all the tested pathogenic bacteria. Conclusions: Our findings revealed that Lactiplantibacillus plantarum To3a and To3d, isolated from tomatoes, stand out as a viable and alternative source of probiotics due to their promising probiotic properties and health-promoting benefits; thus, they may be explored for practical use in novel, locally adaptable functional products.