Biodegradation of DEP, DIBP, and BBP by a psychrotolerant Sphingobium yanoikuyae strain P4: Degradation potentiality and mechanism study.

Phthalic acid esters (PAEs) are human made chemicals widely used as plasticizers to enhance the flexibility of plastic products. Due to the lack of chemical bonding between phthalates and plastics, these materials can easily enter the environment. Deleterious effects caused by this chemo-pollutant have drawn the attention of the scientific community to remediate them from different ecosystem. In this context, many bacterial strains have been reported across different habitats and Sphingobium yanoikuyae strain P4 is among the few psychrotolerant bacterial species reported to biodegrade simple and complex phthalates. In the present study, biodegradation of three structurally different PAEs viz., diethyl phthalate (DEP), di-isobutyl phthalate (DIBP), and butyl benzyl phthalate (BBP) have been investigated by the strain P4. Quantitative analyses through High-performance liquid chromatography (HPLC) revealed that the bacterium completely degraded 1 g/L of DEP, DIBP, and BBP supplemented individually in minimal media pH 7.0 within 72, 54, and 120 h of incubation, respectively, at 28 °C and under shake culture condition (180 rpm). In addition, the strain could grow in minimal media supplemented individually with up to 3 g/L of DEP and 10.0 g/L of DIBP and BBP at 28 °C and pH 7.0. The strain also could grow in metabolites resulting from biodegradation of DEP, DIBP, and BBP, viz. n-butanol, isobutanol, butyric acid, ethanol, benzyl alcohol, benzoic acid, phthalic acid, and protocatechuic acid. Furthermore, phthalic acid and protocatechuic acid were also detected as degradation pathway metabolites of DEP and DIBP by HPLC, which gave an initial idea about the biodegradation pathway(s) of these phthalates.

Biodegradation of di­n­butyl phthalate by psychrotolerant Sphingobium yanoikuyae strain P4 and protein structural analysis of carboxylesterase involved in the pathway.

A priority pollutant Phthalate Esters (PAEs) are widely used as plasticizers and are responsible mainly for carcinogenicity and endocrine disruption in human. For the bioremediation of PAEs, a psychrotolerant Sphingobium yanoikuyae strain P4, capable of utilizing many phthalates di­methyl phthalate (DMP), di­ethyl phthalate (DEP), di­n­butyl phthalate (DBP), di­isobutyl phthalate (DIBP), butyl benzyl phthalate (BBP), and few Polycyclic Aromatic Hydrocarbons as the sole source of carbon and energy was isolated from Palampur, Kangra, Himachal Pradesh, India. 100% utilization of DBP (1 g L-1) by the strain was observed within 24 h of incubation at 28 °C. Interestingly the strain also degraded DBP completely at 20 °C and 15 °C within 36 h and 60 h, respectively. Esterase involved in DBP degradation was found to be inducible in nature and intracellular. Comparative sequence analysis of carboxylesterase enzyme sequences revealed conserved motifs: G-X-S-X-G and -HGG- which were the characteristic peptide motifs reported in different esterases. Structural analysis showed that the enzyme belongs to serine hydrolase superfamily, which has an α/ß hydrolase fold. Interaction and binding of DBP to a catalytic Ser184 residue in the esterase enzyme were also analysed. In conclusion, carboxylesterase possess the required active site which may be involved in the catabolism of DBP.

Molecular insights into the activity and mechanism of cyanide hydratase enzyme associated with cyanide biodegradation by Serratia marcescens.

The present study provides molecular insights into the activity and mechanism of cyanide hydratase enzyme associated with degradation of cyanide compounds, using Serratia marcescens RL2b as a model organism. Resting cells harvested after 20 h achieved complete degradation of 12 mmol l- 1 cyanide in approximately 10 h. High-performance liquid chromatography analysis of reaction samples revealed formation of formamide as the only end product, which confirmed the presence of cyanide hydratase activity in S. marcescens RL2b. Comparative structural analysis with the other nitrilase family proteins, which was carried out using a sequence of cyanide hydratase from a phylogenetically related strain S. marcescens WW4, also revealed subtle but significant differences in amino acid residues of the substrate-binding pocket and catalytic triad (Cys-Lys-Glu).

Profenofos, an Acetylcholinesterase-Inhibiting Organophosphorus Pesticide: A Short Review of Its Usage, Toxicity, and Biodegradation.

Pesticides play an important role in the protection of different crops. Among the diverse sets of pesticides used all over the world, the organophosphates are the most widely used group. Profenofos [O-(4-bromo-2-chlorophenyl) O-ethyl S-propyl phosphorothioate] is one of the most largely used organophosphate insecticides on field crops, vegetables, and fruit crops. The World Health Organization classifies this compound as moderately hazardous (Toxicity Class II), and its residues have been found in vegetables like okra [ (L.) Moench], gooseberries ( sp.), green chilies [ (L.)], curry leaves [ (L.) Spreng], mint leaves [ (L.)], and coriander leaves [ (L.)]. Dietary intake of profenofos (PFF) is the major exposure pathway for humans. When applied to agricultural fields, PFF residues spread into every part of the environment: ambient air, surface water, and soil. In this review, we discuss the worldwide usage of PFF pesticide, its toxic effects on humans and other living organisms in the environment, and biodegradation of this chemical by various microbial strains. To date, no complete biodegradation pathway has been established for PFF pesticide, calling for a study of this nature.