Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
2 results
Search Results
Article Citation - Scopus: 1Esterase-Mediated Degradation of Dibutyl and Diethylhexyl Phthalates in Aqueous and Soil Systems(Elsevier Ltd, 2025) Balci, E.; Sanli-Mohamed, G.; Sofuoglu, A.Phthalate esters (PAEs), widely used as plasticizers, pose severe environmental and health risks. This study investigated the enzymatic hydrolysis of PAE congeners (dibutyl phthalate (DBP) and diethylhexyl phthalate (DEHP)) in aqueous and soil systems using Bacillus subtilis esterase and a new thermoalkaliphilic Geobacillus sp. esterase. A novel esterase secreted from Geobacillus sp. which was isolated from a geothermal region (Türkiye) was expressed in E.coli and purified. Geobacillus sp. esterase was able to degrade almost 30% of DBP and 40% of DEHP (100 mg/L) in the aqueous system within 336 h, while it degraded virtually 59% and 98% of DBP in agricultural area soil (soil-1) and forest area soil (soil-2), respectively, at the same time. To compare with Geobacillus sp. esterase, Bacillus subtilis esterase was used, which fully degraded DBP with 100 mg/L in the soil-1 and soil-2 for 72 h and 2 h, respectively. The performances of both esterases to degrade DEHP (100 mg/L) were similar in soil-1 (∼35%) and soil-2 (∼50%) for 336 h. Soil characteristics significantly influenced PAE degradation. Compared to that in the aqueous system, Geobacillus sp. esterase in soil systems had a higher degradation efficiency. This was likely due to its origin from a soil microorganism. Variations in the degradation ability of two enzymes most probably arose from substrate specificities and enzyme dynamics. Molecular docking results showed that DBP had a higher affinity to both enzymes than DEHP. Overall, this study offers important evidence that Bacillus subtilis esterase and Geobacillus sp. esterase are effective biocatalysts for removing the pollutants with ester bonds in the environment. © 2025 Elsevier LtdBook Part An Effect of Climate Change: Increased Health Risks Due To Arsenic in Drinking Water - the Case of İzmir, Turkey(Nova Science Publishers, Inc., 2010) Sofuoglu, S.C.; Sofuoglu, A.Our previous research (Kavcar et al., 2009) has shown that tap water arsenic concentrations in the City of İzmir, Turkey, was of concern as arsenic in 15 of 37 (41%) of the tap water samples (collected in the year 2004) exceeded the Turkish drinking water standard of 10 µg/L (TMH, 2005). The median, mean, and 95th percentile concentrations were 2.9, 12.0, and 42.0 µg/L, respectively. The violations of the standard were in three districts, i.e., Bornova, Çiğli, and Karşıyaka, that were served primarily by groundwater sources. The concentrations in other districts were below the standard. However, concentrations less than the standard may be associated with a carcinogenic risk that is greater than the acceptable risk level of one in ten thousand depending on the level of exposure, mainly, daily drinking water intake rate and body weight. This was the case for the City of İzmir as lifetime carcinogenic risks exceeded the acceptable level for 19 of the 37 participants (51%). As the result of the above cited research, the local government has shut-down a number of groundwater wells as a mitigation measure. In turn, the concentrations were brought down to <15 µg/L in the three districts by increasing the proportion of surface water supplied from Tahtalı Reservoir. However, climate change has been affecting the region. The water volume in the resevoir was dropped below 5% in 2008. As a result, the arsenic contaminated wells were brought back into the service, causing a sharp increase in the arsenic concentrations, this time all around the city, measured by the local health authority. İzmirians who can not afford to buy bottled drinking water are (to be) exposed to arsenic concentrations of 30-40 µg/L until the planned treatment plant is in place. A probablistic risk assessment was conducted to estimate the human health risks for the scenario of no available surface water, in which no treatment and treatment with 90% and 99% efficiencies were assumed for the arsenic contaminated groundwater, based on the concentrations measured by the local health authority. The median carcinogenic risk estimated for the scenario of no treatment for the metropolitan area was approximately eight times the median value estimated when the main source water was Tahtalı Reservoir, a surface water dam. © 2008 Nova Science Publishers, Inc.