Isolation and Identification of Lactic Acid Bacteria from Okara and Evaluation of Their Potential as Candidate Probiotics
Salam N. Aritonang,
Background: Okara is an industrial waste product resulting from the manufacture of soy milk or tofu. This waste is a pulp consisting of the insoluble parts of the soybean that remain after pureed soybeans are filtered during the production of soy milk and tofu. Okara is not widely used and is dumped into the environment, causing pollution. However, this waste contains nutrients and may be a good medium for the growth and development of microorganisms such as Lactic Acid Bacteria (LAB). Objective: The purpose of this study was to isolate and identify probiotic LAB from okara and determine their antimicrobial activity against pathogenic bacteria (Escherichia coli 0157, Staphylococcus aureus ATCC 25923 and Listeria monocytogenes EP01). Methodology: Isolation and purification of LAB were carried out on MRS agar supplemented with 0.2% CaCO3. Isolates were identified by morphological and physiological tests. Antibacterial activity was tested using the well diffusion method and the obtained data were analyzed descriptively. Twenty-four isolates were grown on MRS agar. Results: Sixteen isolates that exhibited growth at the clear zone were identified as gram positive, catalase-negative homofermentative rod and coccus cells. The results showed that the LAB isolated from okara had the ability to inhibit pathogenic bacteria, causing various clear zone diameters. The survival rates of these isolates under acidic conditions and their tolerance to 0.5% bile salt were varied. Based on the antimicrobial activity and probiotic properties of the LAB isolated from okara, these isolates belong to the species Lactobacillus spentosus and Lactobacillus plantarum. Conclusion: The results showed that the LAB isolated from okara belonged to the species Lactobacillus pentosus and Lactobacillus plantarum. Both species exhibited properties attributed to probiotics.
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