Isolation and Probiotic Characterization of Lactobacillus plantarum from Etawa Goat Milk in Padang, Indonesia

Abstract

Peranakan Etawa (PE) goat milk is a nutrient-rich dairy product that contains beneficial microorganisms with potential probiotic applications. Probiotic bacteria are known to support gut health, inhibit pathogenic microorganisms, and enhance the functional value of food products. However, the characterization of probiotic bacteria isolated from Etawa goat milk in Padang, Indonesia, remains limited. Therefore, this study aimed to isolate, characterize, and evaluate the probiotic potential of lactic acid bacteria obtained from Etawa goat milk collected in Padang, Indonesia. Bacterial isolation was performed using de Man, Rogosa, and Sharpe agar medium, followed by purification and characterization based on colony morphology, Gram staining, microscopic observation, and biochemical analysis through catalase testing. The probiotic properties of the isolates were evaluated by assessing their survival under acidic conditions at pH 3.0, resistance to 0.3% bile salts, and antimicrobial activity against Escherichia coli O157 and Staphylococcus aureus using the agar diffusion method. Three bacterial isolates, designated KG, PD, and EL, were successfully obtained from the milk samples. Among them, isolate PD demonstrated characteristics consistent with lactic acid bacteria, including Gram-positive reaction, rod-shaped morphology, and catalase-negative activity. This isolate showed moderate tolerance to acidic conditions, with a survival rate of 32.50%, and high resistance to bile salts, with a survival rate of 80.60%. In addition, PD isolate exhibited strong antimicrobial activity, producing inhibition zones of 19.19 mm against E. coli O157 and 13.79 mm against S. aureus. Molecular identification based on 16S ribosomal ribonucleic acid gene sequencing revealed 100% similarity to Lactobacillus plantarum strain CAU10666. In conclusion, L. plantarum isolate PD from Peranakan Etawa (PE) goat milk demonstrates promising probiotic potential and may be considered a suitable candidate for future development as a functional food ingredient or probiotic culture.