Malathion Biodegradation by Strain FXJ9.536

Cells of strain FXJ9.536 were resuspended in sterile BM medium (K₂HPO₄ 1.0 g, MgSO₄·7H₂O 1.0 g, (NH₄)₂SO₄ 2.0 g, NaCl 1.0 g, CaCO₃ 2.0 g, ddH₂O 1000 mL, pH 6.4–6.8) to OD₆₀₀ = 0.8. Then, 0.5 mL resuspended inoculum was inoculated into a 10 mL BM medium supplemented with 0.5 g/L yeast extract, 0.5 g/L glucose (both as co-substrates to improve malathion degradation) [27 (link)], and 50 μL malathion solution (20 mg/mL) in a 50-mL erlenmeyer flask, in which the final concentration of malathion was 100 mg/L. The flasks were incubated in the dark at 10 °C or 24 °C, 200 rpm for 7 days. The fermentation was conducted in triplicate. Sterile malathion-BM medium was also run in parallel as acontrol. After fermentation, the residual malathion in broth was extracted by adding an equal volume of n-hexane. After vigorous shaking for 5 min, the organic layer was separated and dehydrated by passing through anhydrous Na₂SO₄. The extracted malathion was analyzed by gas chromatography-mass spectrometry (GC-MS) using Agilent 7200 Q-TOF GC/MS as previously described [40 (link)].