Phthalate ester biodegradation in agricultural soil using exogenous bacterial consortium under fertilizer addition

Abstract

Phthalate esters (PAEs) have been classified as a priority contaminant due to their endocrine-disrupting properties and abundance in the environment. Previously, several PAE-degrading consortia were enriched from landfill soil. This study aimed to initially select a consortium with efficient degradation activity, to characterize based on degradation kinetics and community dynamics, and to evaluate bioaugmentation feasibility while maintaining activity through continuous transfer. It was obtained based on enriched consortium selection that LF-NK-DEHP could simultaneously degrade 92.9% 100 mg l-1 DBP and 63.4% 100 mg l-1 DEHP within seven days. Kinetic degradation revealed DBP degradation by LF-NK-DEHP to fit the modified Gompertz model (R2 = 0.92, t1/2 =1.49 days, 500 mg l-1 DBP). On the other hand, DEHP degradation kinetics fit a zero-order kinetic model (R2 = 0.94, t1/2 =7.23 days, 500 mg l-1 DEHP). Community dynamics study revealed a significant correlation between the genus Microbacterium to DBP degradation and the genus Rhodococcus to DEHP degradation. Genus Pigmentiphaga was reported to correlate with both PAEs. In addition, continuous transfer of LF-NK-DEHP could maintain PAE degradation activity. Bioaugmentation of enriched consortium LF-NK-DEHP revealed insignificant degradation rate compared to natural attenuation. However, fertilizer addition was observed to improve the bioaugmentation performance. Bioaugmentation added with fertilizer could degrade 200 mg kg-1 DEHP up to 75.87% within 25 days while removing 200 mg kg-1 DBP altogether within three days. This was further confirmed through alleviation of PAE intermediates phytotoxicity. Upon completion of this research, new information was acquired, including methods to maintain enriched consortia degradation activity, potential novel PAE-degraders, and feasibility of bioaugmentation with exogenous enriched consortium for PAE bioremediation.