Biodegradation of endocrine disruptor dibutyl phthalate (DBP) by a newly isolated Methylobacillus sp. V29b and the DBP degradation pathway.

Vinay Kumar,S S Maitra

doi:10.1007/s13205-016-0524-5

Abstract

Bacteria of the genus Methylobacillus are methanotrophs, a metabolic feature that is widespread in the phylum Proteobacteria. The study demonstrates the isolation and characterization of a newly isolated Methylobacillus sp. V29b. which grows on methanol, protocatechuate, monobutyl phthalate, dibutyl phthalate, diethyl phthalate, benzyl butyl phthalate, dioctyl phthalate and diisodecyl phthalate. Methylobacillus sp. V29b was characterized with scanning electron microscopy, transmission electron microscopy, Gram staining, antibiotics sensitivity tests and biochemical characterization. It degrades 70 % of the initial DBP in minimal salt medium and 65 % of the initial DBP in samples contaminated with DBP. DBP biodegradation kinetics was explained by the Monod growth inhibition model. Values for maximum specific growth rate (µ max) and half-velocity constant (K s) are 0.07 h−1 and 998.2 mg/l, respectively. Stoichiometry for DBP degradation was calculated for Methylobacillus sp. V29b. Four metabolic intermediates, dibutyl phthalate (DBP), monobutyl phthalate, phthalic acid and pyrocatechol, were identified. Based on the metabolic intermediates identified, a chemical pathway for DBP degradation was proposed. Six genes for phthalic acid degradation were identified from the genome of Methylobacillus sp. V29b.

Highlights

Phthalic acid esters (PAEs) are a class of compounds widely used as plasticizers to provide mechanical strength and flexibility to the resins (Cartwright et al 2000; Staples et al 1997)
V29b. which grows on methanol, protocatechuate, monobutyl phthalate, dibutyl phthalate, diethyl phthalate, benzyl butyl phthalate, dioctyl phthalate and diisodecyl phthalate
The aim of the study was isolation, characterization and identification of efficient dibutyl phthalate (DBP)-degrading bacterial strain from municipal solid waste (MSW) leachate and to examine the degradation potential of the isolate toward degradation of DBP in both minimal media and in PAEscontaminated samples collected from the landfill site

Summary

Introduction

Phthalic acid esters (PAEs) are a class of compounds widely used as plasticizers to provide mechanical strength and flexibility to the resins (Cartwright et al 2000; Staples et al 1997) They are ingredients of paints, adhesives, house-building materials, defoaming agents, PVC pipes, food packing materials, toys, plastics, solubilizers of cosmetic products, medical devices, photography films, textile fabrics, pesticide carriers, lubricating oils and are used in aerospace technology (Gesler 1973; Gross and Colony 1973; Hauser et al 2007; Ito et al 2005; Krauskopf 1973; Marcel 1973; Teil et al 2006; Tepper 1973; Wang et al 1995b; Wilkinson and Lamb 1999). They are known for irritation of eyes, skin, respiratory tract, blurred vision and induce stone formation in the

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