Microbial degradation of flubendiamide in different types of soils at tropical region using lactic acid bacteria formulation

Pesticide residues cause serious harm to human health and the environment. Flubendiamide is a phthalimide insecticide that is more persistent in the soil. Microbes play a significant role in the degradation of pesticides in the soil environment. Lactic acid bacteria (LAB), which are used as probiotics in food preservation, are generally recognized as safe and have the potential to increase the rate of pesticide degradation. To assess the potential of LAB to degrade flubendiamide in soil, a semisolid lactic acid bacterial formulation was prepared by selectively fermenting a mixture of 100 g of milk powder, 1.0 kg of cane jaggery, 100 mL of fermented grape juice and one beaten egg. The prepared LAB formulation contained Lactococcus lactis, Lactobacillus pentosus, and Enterobacter faecalis. The degradation of flubendiamide in three Indian soils was examined under laboratory conditions using this LAB formulation. The flubendiamide and its metabolite, desiodo flubendiamide residues were quantified using ultra high performance liquid chromatography coupled with a photodiode array detector (UHPLC-PDA). The limit of quantification for the analytical method was 0.05 µg/g. Flubendiamide dissipation occurred more rapidly in the soil treated with LAB than in the untreated soil. Significant decrease in the flubendiamide and desiodo flubendiamide residue was observed from 3rd day after treatment in acidic soil, neutral soil and neutral soil with LAB addition (9.84 ± 0.07, 9.93 ± 0.07 and 10.29 ± 0.4 µg/g respectively) compared to soils without LAB (10.14 ± 0.03, 10.07 ± 0.05 and 10.45 ± 0.01 µg/g respectively) resulting in half-life values of 21.66 to 33 days in soils with LAB, compared to 23.90 to 36.47 days in soils without LAB. The degradation of flubendiamide in soils markedly increased in the following order: acidic soil > neutral soil > sodic soil, owing to the higher LAB population present. These results suggest that LAB can be further exploited for bioremediation of flubendiamide contaminated soil.