In this study, we aimed to determine the in vitro activity of Leuconostoc mesenteroides var. mesenteroides isolated from sugar-industry effluents to produce a dextran bioflocculant from sucrose as a low-cost substrate. L. mesenteroides strains present in residual cane juice from a sugar factory were isolated and biochemically identified using Mayeux, Sandine, and Elliker agar (MSE) as a selective medium. The strain number 3 (LM03) was biochemically identified as L. mesenteroides var. mesenteroides, which was used for this study. The concentration of dextran was quantified by dry weight, the morphology and purity were evaluated using Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Flocculation was evaluated via turbidimetric assays in different pH ranges from sugar-industry effluents and doses of dextran. ...