Boron bioremoval by a newly isolated Chlorella sp. and its stimulation by growth stimulators

It has been well documented that excess concentrations of boron (B) causes toxic effects on many of the environmental systems. Although Chlorella sp. has been studied to remove pollutants from water, its capacity to remove B has not been investigated yet. Boron removal levels of newly isolated Chlorella sp. were investigated in BG 11 media with stimulators as triacontanol (TRIA) and/or sodium bicarbonate (NaHCO₃) and without them, to test if they could increase the removal efficiency by increasing biomass. The assays were performed to determine the effect of different medial compositions, B concentrations, pH and biomass concentrations onto removal efficiency. Boron removal was investigated at 5-10 mg/L range at pH 8 in different medial compositions and maximum removal yield was found as 32.95% at 5.45 mg/L B in media with TRIA and NaHCO₃. The effect of different pH values on the maximum removal yield was investigated at pH 5-9, and the optimum pH was found again 8. The interactive effect of biomass concentration and B removal yield was also investigated at 0.386-1.061 g wet weight/L biomass. The highest removal yield was found as 38.03% at the highest biomass range. This study highlights the importance of using new isolate Chlorella sp. as a new biomaterial for B removal process of waters containing B.     

Investigation of sulfur poisoning of CNx oxygen reduction catalysts for PEM fuel cells

The role of the transition metal used during the growth of non-noble metal electrochemical oxygen reduction CN_x catalysts was investigated through sulfur treatment, a well-known poison for transition metal-based catalysts. The intent of sulfur poisoning was to show the existence of an electrocatalytic active site in CN_x that did not depend on iron. The sulfur treatment was shown to be effective on a platinum catalyst, as seen by the decreasing onset potential. The same treatment, however, not only showed no negative effect on the CN_x catalyst, but enhanced its performance, as seen by the increase in the onset potential. This suggests that, if there are iron-based active sites in these catalysts, they are either sulfur tolerant or they do not participate in the electrocatalytic oxygen reduction. The deposition of sulfur onto CN_x catalyst was verified by temperature-programmed oxidation and X-ray photoelectron spectroscopy. Iron K-edge X-ray absorption near edge structural analysis of the CN_x catalyst suggested that the iron phase, which was primarily composed of nanometer-sized metallic particles, was unchanged by sulfur poisoning, suggesting that the residual iron left in these materials is not catalytically accessible.     

Synthesis and Characterization of Silicone-Based Surfactants as Anti-Foaming Agents

Silicone-based amphiphilic surfactants were synthesized as anti-foaming agents through a polycondensation reaction between chlorine-terminated polysiloxane and polyethers. Poly(ethylene glycol) (PEG) and poly(propylene glycol) of different molecular weights were used. The structures of these tri-block co-polymers were characterized by FTIR, ¹H NMR and ESI–MS analysis. Surface tension, foam height and foam destruction properties of these co-polymers were determined. Spectroscopic analysis confirmed that bonding of polyether to polysiloxane was successful and two types of different tri-block co-polymers were obtained. The anti-foaming efficiency of these co-polymers tended to increase with an increase in the hydrophilic character of the co-polymer chains. The synthesized tri-block co-polymers, which can be used as anti-foaming agents in paper-coating applications of poly(vinyl acetate-co-butyl acrylate) latexes, showed low surface tension values, fast liquid drainage and efficient foam destruction. PEG 200-b-PDMS-b-PEG 200 was determined to be the most efficient anti-foaming agent among all co-polymers synthesized.     

Transparent, highly flexible, all nanowire network germanium photodetectors

We report on the fabrication and characterization of all nanowire (NW) network photodetectors. For this purpose, germanium (Ge) NW networks are used as active semiconducting elements, whereas single walled carbon nanotube (SWNT) and silver (Ag) NW networks are used as the contacts. Following their synthesis, all NW networks are deposited through simple solution based methods. Photoresponse characteristics and transparency of the photodetectors for different Ge NW densities are measured. The fabricated devices show a large response with short relaxation times (<10 ms), are flexible and transparent within the visible spectrum.     

α‐Amylase immobilization on functionalized nano CaCO3 by covalent attachment

In this study, α‐amylase was immobilized on glutaraldehyde activated silanized calcium carbonate nanoparticles by a using covalent binding method. The surface modified nano calcium carbonate (CaCO₃) were characterized using FTIR and SEM. Immobilization yield was found as 199.43 mg/g of calcium carbonate nanoparticles. The maximum activity was observed at pH 6.5. The immobilized enzyme had a higher activity at elevated temperature (50–90°C) than the free one. Reuse studies demonstrated that the immobilized enzyme could reuse 25 times while retaining 18.2% of its activity. Free enzyme lost its activity completely within 15 days. V_max values for the free and immobilized enzymes were calculated as 10 and 0.35 mg/mL/min, respectively.     

Synthesis of microbial elastomers based on soybean oil. Autoxidation kinetics,thermal and mechanical properties

Microbial bioelastomers prepared by the autoxidation of the unsaturated medium-long chain length co-poly-3-hydroxyalkanoate’s (mlcl-PHAs) based on soybean oily acids (Sy) have been reported. Pseudomonas oleovorans were grown on a series of the mixture of octanoic acid (OA) and Sy with the weight ratio of 20:80, 28:72 and 50:50 in order to obtain unsaturated mlcl-copolyesters coded PHO-Sy-2080, PHO-Sy-2872, and PHO-Sy-5050, respectively. The microorganism was also grown on the mixture of Sy and 10-undecenoic acid (UA) with the weight ratio of 50:50 to obtain unsaturated copolyester coded PHU-Sy-5050. The PHAs obtained were characterized by ¹H NMR and GC-MS techniques. Double bond contents of the unsaturated PHAs obtained were varying between 0.8 to 20 mol %. Autoxidation of the unsaturated copolyesters were carried out on exposure to air at room temperature in order to obtain new biomaterials whose mechanical strength was improved. Autoxidation kinetics, shelf life, mechanical and thermal properties of these biomaterials were evaluated.     

The use of novel photobleachable phthalocyanines to image DNA

The interaction of cationic photobleachable cobalt 1 and palladium 2 phthalocyanines (pcs) with calf thymus (CT) DNA was investigated by UV/vis spectrophotometric methods and gel electrophoresis. With the addition of pcs, the change in the thermal denaturation profile of DNA was observed. The results indicated that these molecules exhibit efficient DNA binding activity. The new cationic cobalt derivative 1 was characterized by elemental analysis, UV, IR and mass spectrophotometry.     

Influence of atomic force microscopy acquisition parameters on thin film roughness analysis

A reliable procedure for measuring parameters connected to surface roughness is needed to compare the gas sensing properties of various thin films or the effect of different fabrication procedures on the surface roughness and the sensing properties. In this article, we propose to investigate how the acquisition parameters specific to atomic force microscopy investigations such as pixel size, scan area and scan speed influence the roughness parameters, namely root mean square and surface area ratio, commonly used for characterizing the gas sensing properties of porphyrins and other materials.     

Bioremoval of textile dyes with different chemical structures by Aspergillus versicolor in molasses medium

Bioremoval of 17 dyes with different chemical structures by Aspergillus versicolor was detected in this study. Maxilon Red GRL (MR-GRL), Everdirect Fast Black VSF (EFB-VSF) and Brillant Blue R (BB-R) were removed better by fungal mycelia. Optimum pH values were found as 6 for all three dyes. In further experiments in the highest dye concentrations tested in this study, 58.3, 100 and 49% removal yields and 14.8, 12.6, 9.0 q(m) values were found for MR-GRL, EFB-VSF and BB-R, respectively. Chemical oxygen demand (COD) reduction after seven days of incubation period and role of laccase activity of Aspergillus sp. were also investigated. COD reduction and laccase activities were 55.6% and 2.93 U/mL for MR-GRL, 90.7% and 3.0 U/mL for EFB-VSF and 69.0% and 1.79 U/mL for BB-R, respectively. According to these results A. versicolor deserves notable attention for removal of these dyes in wastewater effluents.     

Extracellular enzyme production and enterotoxigenic gene profiles of Bacillus cereus and Bacillus thuringiensis strains isolated from cheese in Turkey

The aim of the present study was to investigate the biochemical characteristics, extracellular enzyme production and enterotoxigenic genes contents of 6 Bacillus cereus and 22 Bacillus thuringiensis strains, isolated from 100 cheese samples in Turkey. Crystal morphologies of B. thuringiensis strains were found either spherical (n = 12) or spherical and irregular-shaped (n = 10) by phase contrast microscopy. B. cereus and B. thuringiensis strains were found to produce extracellular enzymes, respectively: gelatinase (83% and 91%), DNase (83% and 77%), lecithinase (83% and 95%), protease on skim milk agar (100% and 100%), protease on milk agar (100% and 91%), protease on casein agar (83% and 77%), xylanase (100% and 45%), and cellulase (0% and 41%), and amylase (83% and 27%). All of the strains, except for Bt-D1, hydrolyzed Tween 20 (96%), but not Tween 80 or tributyrin. Pectinolytic activity was obtained to be the least frequent (4%). PCR analysis showed that all strains contained nheA, nheB, nheC and hblD genes. The hblA and hblC genes were present in 2 and 4 of B. thuringiensis strains, respectively. The bceT gene was detected in 1 B. cereus and 9 B. thuringiensis strains. The entFM gene was detected more frequently in B. thuringiensis (82%) than in B. cereus strains (50%). To our knowledge, this is the first report about the isolation and identification of enterotoxigenic B. cereus and B. thuringiensis strains from cheese samples in Turkey.