Bioaugmentation of Enterobacter cloacae AKS7 causes an enhanced degradation of low-density polyethylene (LDPE) in soil: a promising approach for the sustainable management of LDPE waste.

Abstract

Enterobacter cloacae AKS7 was previously reported to degrade UV-treated low-density polyethylene (LDPE) more efficiently than UV-untreated LDPE. However, the degradation of LDPE by Enterobacter cloacae AKS7 at the LDPE-contaminated soil remained unaddressed. To address this issue, soil microcosms were prepared in which an equal amount of either UV-treated or UV-untreated LDPE was added. Then, the microcosms were either augmented with AKS7 or left non-augmented. We observed that the bioaugmented microcosms exhibited approximately twofold greater polymer degradation than non-bioaugmented microcosms. To investigate the underlying cause, we found that the abundance of LDPE-degrading organisms got increased by approximately fivefold in bioaugmented microcosms than non-bioaugmented microcosms. The microbial biomass carbon and nitrogen content got enhanced by approximately twofold in bioaugmented microcosms as contrasted to non-bioaugmented microcosms. Furthermore, the bioaugmented microcosms showed almost twofold increase in the level of dehydrogenase and fluorescein diacetate (FDA) hydrolyzing activity than the non-bioaugmented microcosms. To add on, Shannon-diversity index and Gini coefficient were determined in each microcosm to measure the microbial richness and evenness, respectively, using the results of carbon source utilization pattern of BiOLOG ECO plate. The bioaugmented microcosms exhibited ~ 30% higher functional richness and ~ 30% enhanced functional evenness than the non-bioaugmented microcosms indicating the formation of an enriched ecosystem that could offer various functions including polymer degradation. Taken together, the results suggested that Enterobacter cloacae AKS7 could be used as a promising bioaugmenting agent for the sustainable degradation of LDPE waste at a contaminated site.