Biodegradation of phthalates DIBP, DMP, and DEP by Paenarthrobacter sp. strain PH1 - analysis of degradation, pathway, and its bioremediation potentiality in soil microcosm

Abstract

Phthalic acid esters (PAEs), a class of anthropogenic hazardous chemicals, have become one of the lead toxic chemicals on the environmental contamination list. Their weak chemical bonding makes them easily assimilated into the environment, leading to serious environmental concerns. This study assessed the degradation of three low-molecular-weight phthalates, di-isobutyl phthalate (DIBP), diethyl phthalate (DEP), and dimethyl phthalate (DMP), in batch culture and artificial soil microcosms by a gram-positive strain Paenarthrobacter sp. PH1, isolated from a municipal waste dumping site in Chennai, Tamil Nadu, India. An intracellular esterase enzyme activity was found to be involved in phthalate degradation. Quantitative biodegradation analysis, conducted using high-performance liquid chromatography, depicted that the strain PH1 could degrade 1 g/L of DIBP, DEP, and DMP within 24 h, 48 h, and 60 h, respectively, in mineral media under batch shake culture conditions (28 °C, pH 7.0, rpm 180). When a mixture of three phthalates was used as a carbon source, all PAEs were completely degraded within 72 h. Besides that, artificial soil microcosm experiments exhibited that the strain PH1 could significantly degrade 63.38% and 66.89% of DIBP, 65.79% and 69.7% of DEP, and 64.91% and 69.07% of DMP within 12 days in sterile soil and unsterile soil, respectively. This is the first report on mixed phthalates degradation by any single strain in the soil microcosm. The findings highlight the potentiality of the strain PH1 towards the bioremediation of phthalate-contaminated soil, especially under mixed phthalate conditions, making it a potential candidate for multi-phthalate degradation in the soil environment.

Keywords: Paenarthrobacter sp. PH1; Biodegradation; Biodegradation pathway; Esterase; Phthalic acid esters; Soil microcosm.