[Determination and Traceability Analysis of Phthalic Acid Esters in Garlic (Allium stivum L.) from Jiangsu Province, China].

Phthalic acid esters (PAEs) are ubiquitous environmental pollutants and are recognized as a threat to the environment and agricultural product safety across the world. In order to investigate the level of PAEs in garlic, soils, and agricultural films from Pizhou City, Jiangsu province, China, 11 garlic samples, 106 soil samples, and 4 agricultural film samples were collected and analyzed using GC-MS. In addition, the uptake and transport characteristics of six PAEs compounds classified as priority pollutants by the United States Environmental Protection Agency (EPA) in the garlic cultivar Daqingke were investigated under hydroponic conditions. The results indicated that dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) were the dominant PAEs species in garlic cloves of the different garlic varieties from Pizhou City. The average contents of DBP and DEHP in garlic cloves were 0.611 mg·kg-1 and 0.167 mg·kg-1, respectively, which were significantly higher than those of the commercial varieties of garlic. The concentrations of DBP and DEHP differed in three tissues of garlic bulbs, ordered as the skin of garlic bulb>skin of garlic clove>garlic clove. Dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DIBP), DBP, and DEHP were the main PAEs species and were detected in all the surface soils collected from Pizhou City. Compared with the soil allowable concentrations of the six PAEs in the United States, the DMP and DBP concentrations in approximately 100% and 63.2% of soil samples exceeded the recommended allowable concentrations set by the EPA. However, the levels of DEP, DIBP, and DEHP in the soils were below the maximum allowable concentrations set by the EPA. Nevertheless, the average content of DEHP in soils was 486 µg·kg-1 and was found to be much higher than that in the other four PAEs. Six PAEs, including DMP, DEP, DIBP, DBP, butyl benzyl phthalate (BBP), and DEHP, were detected in all the agricultural film samples. Among them, the contents of DBP and DEHP in the agricultural films were the highest, accounting for 53.7%-63.2% of the total PAEs. The amount of PAEs present in the residual film was significantly lower than that in the new film, and all six PAEs were detected in garlic or soil samples, suggesting that agricultural film can be an important source of PAEs in garlic farming soils and garlic. Furthermore, the garlic plants absorbed DMP and DEP efficiently from the substrate and showed higher translocation factors (TFs) for DMP and DEP than those for DBP, BBP, DEHP, and di-n-octyl phthalate (DnOP), resulting in a higher accumulation of DMP and DEP in the over-ground parts of garlic. In contrast, DBP and BBP in roots of garlic displayed higher bioconcentration factors (57.4 and 81.5, respectively) compared to those of the other four PAEs, whereas the TFs of DBP and BBP were lower; this may have contributed to the high accumulation of DBP in garlic bulbs. The BCFs and TFs of DEHP and DnOP in garlic were relatively lower, but the DEHP had been detected in all garlic cloves, which may be a result of the higher DEHP contents in soils.

Biodegradation of dibutyl phthalate by a novel endophytic Bacillus subtilis strain HB-T2 under in-vitro and in-vivo conditions.

The environmental prevalence and potential toxicity of dibutyl phthalate (DBP) motivate the attempt to develop feasible strategies to deal with DBP contamination. In this study, a strain of endphytic bacteria HB-T2 was isolated from sorrel roots and identified as Bacillus sp. by analysing its morphology, physiology, biochemistry and 16S rDNA sequence. The degradation efficiency of DBP by HB-T2 was almost identical under the temperature of 30∼40°C, but was significantly enhanced as the culture pH and inoculum size increases from 6.0 to 8.0, and 1% to 5% respectively. The degradation kinetics of DBP could be well described by the first-order kinetic model, with the degradation half-life ranging from 1.59 to 7.61 h when the initial concentrations of DBP were in the range of 5-20 mg/L. LC-MS analysis of the culture samples taken at varying intervals revealed monobutyl phthalate, phthalic acid and protocatechuic acid as the major metabolic intermediates during the degradation process. HB-T2 exhibited an excellent capability to degrade a wide range of phthalate esters (PAEs), especially butyl benzyl phthalate (BBP), dipentyl phthalate (DPP), and diisobutyl phthalate (DIBP). Inoculation of HB-T2 into Chinese cabbage (Brassica chinensis L.) growing in DBP-contaminated soils could significantly reduce the DBP levels in plant tissues and relieve the phytotoxic effects of DBP. Results of this study highlighted the great potential of this novel endophytic Bacillus subtilis strain HB-T2 for bioremediation of PAEs contamination and improvement of agricultural product safety by reducing PAEs accumulation in edible crops.