Probiotic potentiality, safety profiling and broad-spectrum antibacterial activity of lactic acid bacteria isolated from sour curd (Malda, India)

Lactic acid bacteria (LAB) obtained from fermented foods are recognized as probiotics that offer multiple health advantages and disease-preventing characteristics, like antibacterial properties. The employment of effective probiotic bacteria as dietary supplements has attracted considerable research attention because of their beneficial impacts. This study demonstrates the probiotic characteristics, safety aspects, and antibacterial efficacy of lactobacilli sourced from sour curd samples collected from Malda (West Bengal, India) using in vitro methods. The identity of LAB was verified through 16S-rRNA gene sequencing and subsequent analysis of the phylogenetic tree. The antibacterial activity was evaluated using agar well and agar overlay methods against gram-positive ( Staphylococcus aureus , Bacillus cereus ) and gram-negative ( Escherichia coli , Pseudomonas aeruginosa ) bacterial pathogens. The study identified six lactobacilli strains that exhibited probiotic features and satisfactory safety profiles. Three of these demonstrated notable broad-spectrum antibacterial effects against gram-positive and gram-negative bacterial pathogens, specifically identified as Levilactobacillus brevis LMEM 401B, Lacticaseibacillus casei LMEM 402 A, and Limosilactobacillus fermentum LMEM 403 C. All isolated lactobacilli displayed cumulative probiotic potentials (CPP) between 78 % and 100 %. Additionally, the probiotic LAB enhanced the action of antibiotics against the indicator bacteria. This study highlights locally available sour curd as a good source of probiotics, which could be used alone or in combination with antibiotics as biotherapeutic agents. • Sour curd was assessed as good source of probiotics. • L. brevis , L. casei and L. fermentum were tested as good probiotics. • The probiotic isolates displayed acceptable safety profiles. • The lactobacilli probiotics showed broad spectrum antibacterial activity. • Curd lactobacilli can be used as probiotics for human consumption.