Necdet Sağlam

Biosorption of inorganic mercury and alkylmercury species on to Phanerochaete chrysosporium mycelium

Abstract The biosorption of inorganic mercury (HgCl2), methyl mercury (CH3HgCl) and ethyl mercury (C2H5HgCl) onto the dry biomass of Phanerochaete chryosponum was studied from aqueous media which concentrations in the range of 5–500 mg l−1. The surface charge density varied with pH, and the concentration of mercury species adsorbed significantly increased from pH 3.0 to maximum levels at pH 8.0. The biosorption of mercury ions by Phanerochaete chrysosporium increased as the initial concentration of Hg(II) ion increased in the adsorption medium. A biosorption equilibrium were established after about 6 h, the adsorbed Hg(II) ion did not significantly change further with time. The dissociation constant (kd) values were 72, 63, and 61 mg l−1 for CH3HgCl, C2H5HgCl and for Hg(II), respectively. The maximum biosorption capacity (qm) at pH 7.0 was 79 mg for CH3HgCI, 67 mg for C2H5HgCl and 61 mg for Hg(II) per g of dried fungal biomass. The affinity order of mercury species was CH3HgCl>C2H5HgCl>and Hg(II).

Purification and characterization of superoxide dismutase from Phanerochaete chrysosporium

The superoxide dismutase that protects against oxidative stress of superoxide radicals in living cells was isolated and purified from Phanerochaete chrysosporium and partially characterized. Cells cultivated under optimized growth conditions were distrupted by grinding with glass beads in a mixer-mill. Partial protein precipitation in crude extract was affected by using (NH4)2SO4, polyethylene glycol, and methanol methods. Fractionation of superoxide dismutase was performed by O-diethylaminoethyl-cellulose ion-exchange chromatography, followed by Sephadex G-100 gel-filtration chromatography. Purified enzyme has a molecular weight of 44 000 ± 800 and is comprised of two equal sized subunits each having an Mn element. The optimum pH of purified MnSOD was obtained as 8.8. Enzyme remained stable at pH 7.0–8.8, 25°C and up to 45°C at pH 7.4 for 1 h incubation. The enzyme was insensitive to cyanide, hydrogen peroxide, ditiothreitol, sodium azide, Triton X-100, and β-mercaptoethanol and was sensitive to sodium dodecyl sulfate. Phenylmethylsulfonyl fluoride (2 mM) and iodoacetamide showed only a 15% inhibition effect on the enzyme. Up to 50% activity reduction was observed for 100 mM ionic strength of phosphate and chloride.

Copper Biosorption on Magnetically Modified Yeast Cells Under Magnetic Field

Brewers yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water-based magnetic fluid stabilized perchloric acid. The magnetically modified yeast cells were characterized by scanning electron microscopy (SEM). Cu2+ biosorption properties of magnetically modified yeast cells from synthetic solutions were utilized in a continuous magnetic system. The Cu2+ ion-binding capacity decreased drastically with the increase of the flow rate. The maximum Cu2+ biosorption capacity was obtained to be 1.2 mmol/g at 25°C. Biosorption of Cu2+ increased with increasing pH and then reached almost a plateau value around pH 4.0. The yeast biomass can be easily regenerated by 0.1 M HNO3 with higher effectiveness. Biosorption of heavy metal ions from artificial wastewater was also studied. The biosorption capacities are 0.92 mmol/g for Cu2+, 0.52 mmol/g for Hg2+, and 0.28 mmol/g for Ni2+. Magnetically-modified yeast cells exhibits the following metal ion-affinity sequence: Cu2+ > Hg2+ > Ni2+.

Chitosan nanoparticles enhances the anti-quorum sensing activity of kaempferol.

Quorum sensing (QS) is a cell density dependent expression of species in bacteria mediated by compounds called autoinducers (AI). Several processes responsible for successful establishment of bacterial infection are mediated by QS. Inhibition of QS is therefore being considered as a new target for antimicrobial chemotherapy. Flavonoid compounds are strong antioxidant and antimicrobial agents but their applications are limited due to their poor dissolution and bioavailability. Our objective was to investigate the effect of kaempferol loaded chitosan nanoparticles on modulating QS mediated by AI in model bioassay test systems. For this purpose, kaempferol loaded nanoparticles were synthesized and characterized in terms of hydrodynamic diameter, hydrogen bonding, amorphous transformation and antioxidant activity. QS inhibition in time dependent manner of nanoparticles was measured in violacein pigment producing using the biosensor strain Chromobacterium violaceum CV026 mediated by AI known as acylated homoserine lactone (AHL). Our results indicated that the average kaempferol loaded chitosan/TPP nanoparticle size and zeta potential were 192.27±13.6nm and +35mV, respectively. The loading and encapsulation efficiency of kaempferol into chitosan/TPP nanoparticles presented higher values between 78 and 93%. Kaempferol loaded chitosan/TPP nanoparticle during the 30 storage days significantly inhibited the production of violacein pigment in Chromobacterium violaceum CV026. The observation that kaempferol encapsulated chitosan nanoparticles can inhibit QS related processes opens up an exciting new strategy for antimicrobial chemotherapy as stable QS-based anti-biofilm agents.

Students’ understanding of genetics concepts: the effect of reasoning ability and learning approaches

Students tend to learn genetics by rote and may not realise the interrelationships in daily life. Because reasoning abilities are necessary to construct relationships between concepts and rote learning impedes the students’ sound understanding, it was predicted that having high level of formal reasoning and adopting meaningful learning orientation would improve students’ understanding of genetics concepts. To test this hypothesis, relationships among students’ understanding of genetics concepts, reasoning ability and learning approaches were investigated. A total of 586 eleventh-grade students participated in the study. Students’ reasoning ability and learning orientation were measured using the Test of Logical Thinking and the Learning Approach Questionnaire, respectively. Students’ understanding of fundamental genetics concepts was assessed using the Two-tier Genetics Concepts Test. Regression analyses were conducted to examine predictive influence of reasoning ability and learning orientations on students’ understanding of genetics concepts. The results revealed that all cognitive variables investigated accounted for a statistically significant portion (27%) of the variance in students’ understanding of genetics concepts. Reasoning ability and meaningful learning orientation predicted students’ understanding of genetics concepts in a positive direction, rote learning orientation predicted it in a negative direction. Additionally, the results indicated that reasoning ability explained more of the variance in test scores as compared to learning approaches.

Partitioning of industrial cellulase in aqueous two-phase systems from Trichoderma viride QM9414

The partition of cellulase from Trichoderma viride in aqueous two-phase systems has been investigated with the purpose of designing a phase system for the bioconversion of cellulose. The partitioning of the enzyme in the two-phase systems composed of various water-soluble polymeric compounds, and the influence of polymer molecular mass on polymer concentration are studied. Systems based on dextran and polyethylene glycol (PEG) proved to be optimal for partitioning the enzyme to the bottom phase which is rich in dextran T500. Cellulases produced by Trichoderma viride grown on Solka-Floc BW200 were fractionated by ammonium sulphate (50%) and purified by chromatography on DEAE–Sephadex A50. The overall purification steps showed a protein reduction of 97% of the original protein content of the culture filtrate. On the other hand, the specific activity (FPU) was increased 24-fold. In optimization experiments, the maximum enzyme activity was found at pH 4.8 when incubated at 28°C for 11 days.

Innovation of Strategies and Challenges for Fungal Nanobiotechnology

Nanotechnology involves the study and use of materials under the 100 nm scale, exploiting the different physiochemical properties exhibited by these materials at the nanoscale level. Microorganisms are the best model and role of action for the nano/biotechnological applications. This technology has become increasingly important for the biotechnology and the related sectors. Promising applications have been already employed in the areas of drug delivery systems using bioactive nanoencapsulation, biosensors to detect and quantify pathogens, chemical and organic compounds, alteration of food compositions, and high-performance sensors and film to preserve fruits and vegetables. Moreover, the taste of food and food safety can be improved by new nano-materials from the microbiological sources. The huge benefits from this technology have led to increases in the market investments in nanoscience and nanoproducts in several areas.

Surface-modified bacterial nanofibrillar PHB scaffolds for bladder tissue repair

The aim of the study is in vitro investigation of the feasibility of surface-modified bacterial nanofibrous poly [(R)-3-hydroxybutyrate] (PHB) graft for bladder reconstruction. In this study, the surface of electrospun bacterial PHB was modified with PEG- or EDA via radio frequency glow discharge method. After plasma modification, contact angle of EDA-modified PHB scaffolds decreased from 110 ± 1.50 to 23 ± 0.5 degree. Interestingly, less calcium oxalate stone deposition was observed on modified PHB scaffolds compared to that of non-modified group. Results of this study show that surface-modified scaffolds not only inhibited calcium oxalate growth but also enhanced the uroepithelial cell viability and proliferation.

Kaempferol loaded lecithin/chitosan nanoparticles: preparation, characterization, and their potential applications as a sustainable antifungal agent

Abstract Flavonoid compounds are strong antioxidant and antifungal agents but their applications are limited due to their poor dissolution and bioavailability. The use of nanotechnology in agriculture has received increasing attention, with the development of new formulations containing active compounds. In this study, kaempferol (KAE) was loaded into lecithin/chitosan nanoparticles (LC NPs) to determine antifungal activity compared to pure KAE against the phytopathogenic fungus Fusarium oxysporium to resolve the bioavailability problem. The influence of formulation parameters on the physicochemical properties of KAE loaded lecithin chitosan nanoparticles (KAE-LC NPs) were studied by using the electrostatic self-assembly technique. KAE-LC NPs were characterized in terms of physicochemical properties. KAE has been successfully encapsulated in LC NPs with an efficiency of 93.8 ± 4.28% and KAE-LC NPs showed good physicochemical stability. Moreover, in vitro evaluation of the KAE-LC NP system was made by the release kinetics, antioxidant and antifungal activity in a time-dependent manner against free KAE. Encapsulated KAE exhibited a significantly inhibition efficacy (67%) against Fusarium oxysporium at the end of the 60 day storage period. The results indicated that KAE-LC NP formulation could solve the problems related to the solubility and loss of KAE during use and storage. The new nanoparticle system enables the use of smaller quantities of fungicide and therefore, offers a more environmentally friendly method of controlling fungal pathogens in agriculture.

Phanerochaete Chrysosporium Loaded Cryogel Column for Biosorption of Mercury (II) Ions from Aqueous Solutions

Bu çalışmanın amacı, Phanerochaete chrysosporium yüklü mololitik kompozit kriyojel kolonlarla sulu ortamlardan Hg iyonlarının uzaklaştırılma potansiyelini araştırmaktır. Yüklü olmayan kolonun şişme derecesi 7.12 g H 2 O/g iken kompozit kolonun şişme derecesi 6.68 g H 2 O/g’dır. Kolonun optimum çalışma koşulları belirlenmiştir. Kolonun tekrar kullanılabilirliği incelenmiş ve sonuçlar bu özgül kolonun Hg biyosorpsiyon kapasitesinde önemli bir azalma gözlenmeden defalarca kullanılabileceğini göstermiştir. Yapay atık su çalışmaları da uygulanmış ve bu sistem için Hg için biyosorpsiyon kapasitesi 75.22 mg/g olarak bulunmuştur.