Sterculic acid methyl ester, an ester derivative of sterculic acid known for inhibiting Δ9 desaturase, has been found to adversely affect and exhibit toxicity towards R. opacus bacteria at a concentration of 0.75 mM. It not only hampers bacterial growth but also modifies fatty acid composition by reducing stearate and oleate levels, increasing the palmitate ratio, and decreasing overall fatty acid content at 0.25 or 0.5 mM concentrations. Additionally, at 50 ppm, Sterculic acid methyl ester enhances the tumor growth-promoting effects of aflatoxin Q1 in rainbow trout, indicating a synergistic interaction between the two compounds. [Matreya, LLC. Catalog No. 1236]