Free radical scavenging and antimicrobial activities of lactic acid bacteria isolated from Indonesian traditional fermented soy food against food-borne pathogens

Abstract Oncom, dage , and gembus are Indonesian local soy food traditionally made from by-products of tofu industries through a microbial fermentation. Lactic acid bacteria (LAB) are one of the microorganisms that grow during the fermentation process, which can affect the nutrition and quality of the soyfood product. Therefore, this study aims to investigate the diversity of LAB from traditional fermented soyfood, antioxidant, and antimicrobial activities. The isolation results obtained three isolates from oncom (OCM01, OCM02, OCM03), two isolates from dage (DG04, DG05) and two isolates from gembus (GMB06, GMB07). All seven isolates were Gram-positive and catalase-negative bacteria. Antibacterial tests against Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 25923 showed supernatant isolate GMB06 at 50% concentration had the highest antibacterial activity with 79.02% and 80.78%, respectively. The results of the DPPH antioxidant test showed that the supernatant of isolate DG05 had the highest IC50 value at a concentration of 1.94 ± 0.05%. The ABTS antioxidant test results showed supernatant isolate GMB07 had the highest IC50 value at a concentration of 0.25 ± 0.7%. These results indicated that the various selected strains may possess antimicrobial and antioxidant potential for the development of functional probiotics.