摘要:Background and Objective: Whey is a byproduct of the cheese industry in Indonesia, while buttermilk is a byproduct from processing butter that has not been used in Indonesia. Whey and buttermilk residues have a very high nutrient value, especially for the growth of microbes. Lactobacillus plantarum ( L. plantarum ) IIA-1A5 is a lactic acid bacteria that was isolated from Indonesian local beef, Peranakan Ongole (PO). The availability of nutrients in whey and buttermilk provides an opportunity to utilize both as economically valuable growth media specifically for L. plantarum IIA-1A5. The objective of this research was to evaluate the L. plantarum IIA-1A5 fermentation pattern by using different growth media, whey but termilk and whey+skim (whey that was enriched by skimmed milk). Materials and Methods: Lactobacillus plantarum IIA-1A5 was grown in 3 different media: whey buttermilk and whey enriched by skim milk. The bacterial population and pH value were analyzed every 4 h during fermentation. The chemical composition of each media was determined. The best growth media was selected based on the growth rate and generation time of L. plantarum IIA-1A5 during fermentation. Crude antibacterial substances were collected from the best media and analyzed for antimicrobial activity against pathogenic bacteria . Results: Whey and buttermilk had a good nutritive value , including a high amino acid content and allowed complete growth of L. plantarum IIA-1A5. Whey+skim was the best growth medium for L. plantarum IIA-1A5 based on the bacterial generation time, which reached 1.96 h. Lactobacillus plantarum IIA-1A5 produced an antimicrobial substrate during a 20 h fermentation process. The cell-free supernatant, as an antimicrobial substrate, could inhibit pathogenic bacteria such as Staphylococcus aureus and Escherichia coli . Conclusion: The best medium for L. plantarum growth was whey+skim, based on the growth media composition, LAB population, growth rate, generation time and antimicrobial activities.