Reyhan Gul Guven

Barrier height enhancement of metal/ semiconductor contact by an enzyme biofilm interlayer

A metal/interlayer/semiconductor (Al/enzyme/p-Si) MIS device was fabricated using α-amylase enzyme as a thin biofilm interlayer. It was observed that the device showed an excellent rectifying behavior and the barrier height value of 0.78 eV for Al/α-amylase/p-Si was meaningfully larger than the one of 0.58 eV for conventional Al/p-Si metal/semiconductor (MS) contact. Enhancement of the interfacial potential barrier of Al/p-Si MS diode was realized using enzyme interlayer by influencing the space charge region of Si semiconductor. The electrical properties of the structure were executed by the help of current–voltage and capacitance–voltage measurements. The photovoltaic properties of the structure were executed under a solar simulator with AM1.5 global filter between 40 and 100 mW/cm2 illumination conditions. It was also reported that the α-amylase enzyme produced from Bacillus licheniformis had a 3.65 eV band gap value obtained from optical method.

Purification and characterization of thermostable and detergent-stable α-amylase from Anoxybacillus sp. AH1.

A thermostable and detergent-stable α-amylase from a newly isolated Anoxybacillus sp. AH1 was purified and characterized. Maximum enzyme production (1874.8 U/mL) was obtained at 24 h of incubation. The amylase was purified by using Sephadex G-75 gel filtration, after which an 18-fold increase in specific activity and a yield of 9% were achieved. The molecular mass of the purified enzyme was estimated at 85 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimum pH and temperature values of the enzyme were 7.0 and 60 °C, respectively. The enzyme was highly stable in the presence of 30% glycerol, retaining 85% of its original activity at 60 °C within 120 min. Km and vmax values were 0.102 µmol and 0.929 µmol/min, respectively, using Lineweaver-Burk plot. The enzyme activity was increased by various detergents, but it was significantly inhibited in the presence of urea. Mg2+ and Ca2+ also significantly activated α-amylase, while Zn2+, Cu2+ and metal ion chelators ethylenediaminetetraacetic acid (EDTA) and 1,10-phenanthroline (phen) greatly inhibited the enzyme activity. α-Amylase activity was enhanced by β-mercaptoethanol (β-ME) and dithiothreitol (DTT) to a great extent, but inhibited by p-chloromercuribenzoic acid (PCMB). Iodoacetamide (IAA) and N-ethylmaleimide (NEM) had a slight, whereas phenylmethylsulfonyl fluoride (PMSF) had a strong inhibitory effect on the amylase activity.

Thermophilic and Halophilic Microorganisms Isolated from Extreme Environments of Turkey, with Potential Biotechnological Applications

Turkey has a great number of different ecological areas, owning over 200 hot water resources and various hypersaline environments with a broad microbial diversity and opportunities for newly isolated microorganisms from extreme environments for many industrial applications. A variety of thermophilic and halophilic microorganisms in different regions of Turkey have been isolated and identified. The thermophilic bacterial members studied were Anoxybacillus, Geobacillus, Bacillus, Brevibacillus, and Aeribacillus belonging to the Bacillaceae family and the other thermophiles such as Thermus and Thermomonas, whereas the isolated halophilic microorganisms were mainly found to be members of the archaeal family Halobacteriaceae or grouped into bacterial phylum Bacteroidetes. In summary, the present study reviews on (1) isolating and identifying thermophiles and halophiles single or as community from various extreme habitats in Turkey based on conventional (morphological, physiological and biochemical tests) and/or molecular methods, (2) screening these extremophiles for industrially important enzymes, (3) studying other novel products and their use in other areas of biotechnology, and finally (4) discussing about the development strategies and the future perspectives on poorly studied extremophilic microorganisms in the country to fulfill future biotechnological and industrial demands.