Two-stage inoculation of partially antagonistic Bacillus sp. strains improves imidacloprid pesticide degradation and humic acid formation during vegetable waste composting

Résumé fourni par la source

While phased inoculation has been demonstrated to accelerate compost maturation, its potential effects on detoxifying pesticide-laden vegetable waste remains to be demonstrated. The objective of this study was to determine the efficacy of two-stage inoculation on composting imidacloprid (IMI)-spiked vegetable waste, employing four lignocellulose-degrading Bacillus strains from our strain collection. In IMI-containing mineral salt medium, B. stratosphericus strain M1, B. licheniformis strain Q1, B. subtilis strain QK, and B. altitudinis strain F11 were all individually capable to degrade the pesticide, in decreasing order, with removal efficiencies between 51 % and 10 %. A combined mixture M, used as a first inoculum for composting, excluded strain F11, due to antagonistic growth effects. After 7 days of composting, a secondary inoculation with strain F11 was applied. This two-stage inoculation (MF) enhanced IMI degradation compared to the non-inoculated control and single-stage inoculation with M, reducing IMI half-life by 8.7 days and 1.5 days, respectively. When composting was complete, MF had achieved 81 % IMI degradation, with exogenous bacteria contributing 77 % of the removal efficiency, 63 % higher than the M treatment. Additionally, MF increased the final humic acid content and polymerization degree by 17 % and 25 %, respectively, compared to M treatment, while reducing the fulvic acid content. Multiple linear regression confirmed that fulvic acid content and IMI residue concentrations were significant factors affecting humic acid content in inoculated treatments. This study shows that two-stage inoculation can provide dual benefits of accelerating vegetable waste composting and detoxifying pesticide residues, offering an efficient strategy for sustainable agricultural waste management.

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