Malathion degradation by soil isolated bacteria and detection of degradation products by GC-MS

Malathion in-vitro biodegradation study was conducted in liquid medium with five bacterial strains labeled S1, S2, S3, S4 and S5 isolated from newly reclaimed agricultural soil. Malathion residues were measured at successive intervals until 30 days after incubation, paralleled with control samples. Malathion Recovery rate was performed at 0.1 and one mg kg⁻¹, achieved values were 91.30 and 98.70%, respectively, limit of detection (LOD) was 0.03 mg kg⁻¹ while limit of quantification (LOQ) was 0.1 mg kg⁻¹. Malathion half-life values (RL50) were 16.68, 20.27, 21.33, 12.72 and 12.49 days for S1, S2, S3, S4 and S5, respectively and control value was 27.50 days. No significant effect on malathion occurred with S2 (Bacillus amyloliquefaciens) and S3 (Staphylococcus sciuri) treatments. S1 (Pseudomonas aeruginosa), S4 (Bacillus pseudomycoides) and S5 (Bacillus licheniformis) treatments showed significant effect that increased malathion degradation rate compared to control treatment. Two main degradation products resulted from bacterial degradation, namely malathion monocarboxylic (MMA) and malathion dicarboxylic acid (MDA), the first one may convert to the latest one over time. Some other degradation products may occur such as ethyl hydrogen fumarate (EHF) but in negligible amount.