<![CDATA[Escherichia coli contamination in food products has created a need to identify natural biological preservatives. Fermentation of tempeh substrates is known to trigger the synthesis of bioactive compounds capable of inhibiting or killing microorganisms. This in vitro study aimed to evaluate the antibacterial activity of an ethanolic extract derived from a mixed-substrate tempeh (soybean and peanut in a 1:1 ratio) against E. coli ATCC 25922. Testing was conducted using the paper disc diffusion method at concentrations of 25%, 50%, and 75%, with amoxicillin serving as the positive control. Observations revealed mean clear zones of 6.33 ± 0.58 mm, 6.66 ± 1.15 mm, and 9.33 ± 1.15 mm for the 25%, 50%, and 75% concentrations, respectively. All extract treatments fell into the moderate inhibition category, whereas amoxicillin produced a zone of 7.67 ± 1.15 mm. The Kruskal-Wallis test yielded a p-value of 0.067 (p > 0.05), demonstrating that increasing the extract concentration did not result in a statistically significant difference in the extent of bacterial inhibition. It is concluded that the mixed-substrate tempeh extract shows preliminary potential for suppressing E. coli; however, varying the concentration up to 75% did not yield a significant increase in effectiveness.]]>
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