Biocontrol of Fusarium species by a novel lectin with low ecotoxicity isolated from Sebastiania jacobinensis

A lectin from Sebastiania jacobinensis bark was isolated using a combination of acetone precipitation, ammonium sulphate fractionation, ion exchange and gel filtration chromatographies. The lectin purified, with a molecular mass of 52.0 kDa and composed of two subunits of 24 kDa, is a glycoprotein with a neutral carbohydrate content of 6.94%. The lectin shows maximum activity over the pH range 4.0–7.5 and heat stability up to 70 °C. Our results show that the lectin is an incompetitive inhibitor for trypsin, with a Ki of 0.39 ± 0.02 μM. Fluorescence spectroscopy indicated the existence of a hydrophobic surface. The percentages of secondary structure are 75% α-helix, 10% β-sheet, 5% β-turn and 10% unordered. Lectin inhibits the mycelial growth of Fusarium moniliforme and Fusarium oxysporum with an IC50 value of 123 ± 0.5 and 303 ± 0.9 μg, respectively. Artemia salina Leach and embryos of Biomphalaria glabrata are not affected by the lectin, indicating low environmental toxicity. Alternative viewpoints are presented that might hopefully help in future efforts to develop safer and more effective microbial control agents.