Improved biodegradation of 1, 2, 4-trichlorobenzene by adapted microorganisms in agricultural soil and in soil suspension cultures

Abstract

Inoculating soil with an adapted microbial community is a more effective bioaugmentation approach than inoculation with pure strains in bioremediation. However, information on the potential of different inocula from sites with varying contamination levels and pollution histories in soil remediation is lacking. The objective of the study was to investigate the potential of adapted microorganisms in soil inocula, with different contamination levels and pollution histories, to degrade 1,2,4-trichlorobenzene (1,2,4-TCB). Three different soils from chlorobenzene-contaminated sites were inoculated into agricultural soils and soil suspension cultures spiked with 1,2,4-TCB. The results showed that 36.52% of the initially applied 1,2,4-TCB was present in the non-inoculated soil, whereas about 19.00% of 1,2,4-TCB was present in the agricultural soils inoculated with contaminated soils after 28 days of incubation. The soils inoculated with adapted microbial biomass (in the soil inocula) showed higher respiration and lower 1,2,4-TCB volatilization than the non-inoculated soils, suggesting the existence of 1,2,4-TCB adapted degraders in the contaminated soils used for inoculation. It was further confirmed in the contaminated soil suspension cultures that the concentration of inorganic chloride ions increased continuously over the entire experimental period. Higher contamination of the inocula led not only to higher degradation potential but also to higher residue formation. However, even inocula of low-level contamination were effective in enhancing the degradation of 1,2,4-TCB. Therefore, applying adapted microorganisms in the form of soil inocula, especially with lower contamination levels, could be an effective and environment-friendly strategy for soil remediation.