Biodegradation of dibutyl phosphite by Sphingobium sp. AMGD5 isolated from aerobic granular biomass

• Cultivated aerobic granular sludge by feeding DBHP as cosubstrate.
• Microbial degradation of dibutyl phosphite for the first time.
• Sphingobium sp. utilised dibutyl phosphite as the sole carbon and phosphorous source.
• Phosphite was utilised as the phosphorous source by Sphingobium sp.
• High phosphatase activity in dibutyl phosphite grown Sphingobium sp. cells.

In the present study, cultivation of aerobic granular biomass capable of biodegradation of dibutyl phosphite, an organophosphite, and isolation of dibutyl phosphite degrading bacterial strains, are reported for the first time. The strain AMGD5, identified as Sphingobium sp., based on 16S rRNA sequencing, degraded dibutyl phosphite efficiently and utilised it as the sole source of carbon and phosphorus. Microbial degradation of dibutyl phosphite caused a significant decrease in medium pH, leading to cessation of growth and further degradation of dibutyl phosphite. Under buffered conditions, complete degradation of up to 3 mM of dibutyl phosphite was achieved within 60 h. The strain showed almost similar growth pattern when either phosphite or dibutyl phosphite was used as the phosphorous source. A 4-fold enhancement in phosphatase activity was evident in dibutyl phosphite fed cells, implying their role in dibutyl phosphite degradation. Sphingobium sp. AMGD5 can be a potential candidate for bioremediation of dibutyl phosphite contaminated waters or sites.