Heterologous expression, purification, and characterization of thermo- and alkali-tolerant laccase-like multicopper oxidase from Bacillus mojavensis TH309 and determination of its antibiotic removal potential.

Laccases or laccase-like multicopper oxidases have great potential in bioremediation to oxidase phenolic or non-phenolic substrates. However, their inability to maintain stability in harsh environmental conditions and against non-substrate compounds is one of the main reasons for their limited use. The gene (mco) encoding multicopper oxidase from Bacillus mojavensis TH309 were cloned into pET14b( +), expressed in Escherichia coli, and purified as histidine tagged enzyme (BmLMCO). The molecular weight of the enzyme was about 60 kDa. The enzyme exhibited laccase-like activity toward 2,6-dimethoxyphenol (2,6-DMP), syringaldazine (SGZ), and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). The highest enzyme activity was recorded at 80 °C and pH 8. BmLMCO showed a half-life of ~ 305, 99, 50, 46, 36, and 20 min at 40, 50, 60, 70, 80, and 90 °C, respectively. It retained more than 60% of its activity after pre-incubation in the range of pH 5-12 for 60 min. The enzyme activity significantly increased in the presence of 1 mM of Cu2+. Moreover, BmLMCO tolerated various chemicals and showed excellent compatibility with organic solvents. The Michaelis constant (Km) and the maximum velocity (Vmax) values of BmLMCO were 0.98 mM and 93.45 µmol/min, respectively, with 2,6-DMP as the substrate. BmLMCO reduced the antibacterial activity of cefprozil, gentamycin, and erythromycin by 72.3 ± 1.5%, 79.6 ± 6.4%, and 19.7 ± 4.1%, respectively. This is the first revealing shows the recombinant production of laccase-like multicopper oxidase from any B. mojavensis strains, its biochemical properties, and potential for use in bioremediation.

Optimization of the anaerobic fermentation process for phosphate release using food waste.

Phosphorus (P) problem worries the whole world due to the increasing demand for finite and non-renewable natural phosphate resources and the inadequacy of sustainable phosphate production technologies. In this study, bio-acidification processes using waste sludge and food waste for simultaneous sustainable phosphate release and biogas production were investigated. Response surface methodology (RSM) was used for bio-acidification optimization. High performance was achieved with the addition of 10% FW and a temperature of 45 °C, which provided 5.30 pH and 371 mg/L P release for 10 days. A total of 196 mL of cumulative biogas was produced. Using food waste potentially reduces operating costs, eliminating the need for external chemical additions for pH control. Also, this approach offers benefits such as waste management, recovery of valuable resources, cost reduction, and environmental friendly.

Polycyclic aromatic hydrocarbons (PAHs) determined by pine needles and semipermeable membrane devices along an altitude profile in Taurus Mountains, Turkey.

Polycyclic aromatic hydrocarbons (PAHs) were analyzed at different altitudes of Taurus Mountains in semipermeable membrane devices (SPMD) and in half-, one-and-a-half-, and two-and-a-half-year-old pine needles. SPMDs were deployed for three different exposure periods: March to September (Summer), September to March (Winter), and March to March (whole year) at eight sites where needle samples were collected. The values of PAHs in needles were between 4.4 to 6066 pg g/fw in half-year-old, 7.2 to 111,115 pg g/fw in 1.5-year-old, and 9.7 to 85,335 pg g/fw in 2.5-year-old needles. Mass of PAHs collected by SPMDs varied from

The occurrence and environmental effect of persistent organic pollutants (POPs) in Taurus Mountains soils.

PURPOSE: Persistent organic pollutants (POPs) are of global concern due to their ubiquitous presence and toxicity. The occurence of polychlorinated dibenzo-p-dioxins (PCDDs), -dibenzofurans (PCDFs), co-planar biphenyls (PCBs), hexachlorocyclohexanes (HCH), dichlorodiphenyltrichloroethanes (DDT), and organochlorine pesticides (OCPs) in forest soil collected from Taurus mountains may have adverse effects on the environment and health. The aim of the study was to investigate the outcome and distribution of POPs in the environment and the possible grasshopper effect along an altitude transect from sea level up to nearly 2,000 m a.s.l at a spatial distance of about 60 km in the southeastern Turkish Mediterranean Sea. METHODS: The samples were collected at a height of 121, 408, 981, 1,225, 1,373, 1,639, and 1,881 m above sea level from Taurus Mountains, Turkey. The results were confirmed using high-resolution gas chromatography-high-resolution mass spectrometry. RESULTS: The levels of the PCDD in forest soil from Taurus Mountains varied from nearly 4 to 12 pg g(-1) dry weight (dw). PCDF concentrations ranged from 2 to 7 pg g(-1) dw. Considerably high DDT levels detected in five stations indicated (3,223-24,564 pg g(-1)) its extensive local application or atmospheric transport. PCB levels were determined between 80 and 288 pg g(-1) dw. HCH concentrations ranged from 141 to 1,513 pg g(-1) dw. The other OCP was between 102 and 731 pg g(-1). CONCLUSION: Although the use of POPs has been banned, our results show that they could still be found in Turkey. Their presence may be attributed to the degradation of pesticides which are newly banned and, as well as to the atmospheric migration and deposition. The lattitude of sampling sites, the chemical, and physical parameters of soil have observed no effect on the fate of POPs in the environment.

Chromium(VI) bioremoval by Pseudomonas bacteria: role of microbial exudates for natural attenuation and biotreatment of Cr(VI) contamination.

Laboratory batch and column experiments were conducted to investigate the role of microbial exudates, e.g., exopolymeric substance (EPS) and alginic acid, on microbial Cr(VI) reduction by two different Pseudomonas strains (P. putida P18 and P. aeuroginosa P16) as a method for treating subsurface environment contaminated with Cr(VI). Our results indicate that microbial exudates significantly enhanced microbial Cr(VI) reduction rates by forming less toxic and highly soluble organo-Cr(III) complexes despite the fact Cr(III) has a very low solubility under the experimental conditions studied (e.g., pH 7). The formation of soluble organo-Cr(III) complexes led to the protection of the cells and chromate reductases from inactivation. In systems with no organic ligands, soluble organo-Cr(III) end products were formed between Cr(III) and the EPS directly released by bacteria due to cell lysis. Our results also provide evidence that cell lysis played an important role in microbial Cr(VI) reduction by Pseudomonas bacteria due to the release of constitutive reductases that intracellularly and/or extracellularly catalyzed the reduction of Cr(VI) to Cr(III). The overall results highlight the need for incorporation of the release and formation of organo-Cr(III) complexes into reactive transport models to more accurately design and monitor in situ microbial remediation techniques for the treatment of subsurface systems contaminated with Cr(VI).