Immobilization of whole yeast cells (Saccharomyces cerevisiae) in calcium alginate is well known. The present work describes the feasibility of gel entrapment of whole cell yeast using strontium, barium, calcium-strontium, calciumbarium and strontium-barium alginates.Bioprocessing of materials is an important area of research in biotechnology. In this regard enzymes, plant, animal and microbial cells, cell organelles, catalytic antibodies and RNAs play a vital role in the bioprocess industries, where ecofriendly processes are mandatory.In continuation of our work (Meena & Raja 2004) on enzymes and cell immobilization techniques, dry yeast cells (Saccharomyces cerevisiae) were studied for their suitability for large scale sucrose inversion using both free and immobilized forms as viable and non-viable cells.Saccharomyces cerevisiae has GRAS (generally recognized as safe) status, and has the toughest cell wall among microorganisms hitherto reported, with a characteristic chemical combination of glucans and mannoproteins (Schreuder et al. 1996). Therefore different research groups have developed many ingenious methods for immobilization. In this research, techniques (Smidsord & Skjak-Braek 1990) such as adsorption on porous materials and gel entrapment of yeast cells are widely used. Survey of literature has revealed that Ca-alginate gels have been employed as gel entrappers for yeast cells (Smidsord & Skjak-Braek 1990). This prompted us to develop other hitherto untested alkaline earth-metal alginates and their mixed alginates as gel entrapment systems for whole yeast cell immobilization.In the present communication we report entrapment and invertase activities of whole cell yeasts in terms of Michaelis-Menten constant (K m ) and pH optima at room temperature for strontium alginate or barium alginate or their mixed alginates.Sodium alginate, sucrose and all other chemicals were procured from S.D.Fine Chemicals or Qualigens. Bakers yeast was procured from a local chemist's shop.A mixture of 1 g bakers yeast and 25 ml of 3.6% (w/v) sodium alginate solution was reacted with 4% (w/v) calcium chloride solution to give yeast whole cellentrapped beads, which were repeatedly washed with water and then suspended in it for determination of yeast invertase activity. Similarly Sr-alginate and Ba-alginate beads entrapping yeast cells were prepared. The mixed metal alginate beads of any of the above two metals were also prepared using 1:1 aqueous solution of respective metal chlorides. The beads so obtained were subjected to invertase activity studies to determine K m values at optimum pH and room temperature using 0.06 M sucrose as substrate.The pH optima for whole cell yeast were determined using 0.1 M citrate-phosphate buffer at different pH values and observed to be at pH 10. The invertase activity of whole yeast viable cells was then determined at room temperature to have K m 10.6 mM at pH 10.0. Immobilization of these viable yeast cells in Ca, Ba, Sr-alginate systems gave inconsistent and irreproducible experimental result...
In recent times, catheters with integrated transducers have been extensively investigated in the field of biomedical engineering, especially for use in in vivo neonatal intensive care systems. An integral module of such systems is a blood pressure sensor that must fulfill the competing requirements of high sensitivity and small area. Typically, microelectromechanical systems-based membrane structures with integrated piezoresistors are used to realize such miniaturized blood pressure sensors. Conventionally, the electromechanical transduction of membrane deformation into an equivalent electrical signal is accomplished by piezoresistors connected in a fully active Wheatstone bridge configuration. However, such a configuration requires a large area for the placement of piezoresistors and layout of interconnects. Even though piezoresistors connected in a half-active Wheatstone bridge configuration overcome the area constraint, such an arrangement still suffers from reduced electrical sensitivity. In this paper we propose a novel three-terminal single-element piezoresistor membranebased miniaturized blood pressure sensor for less than 1 French catheter application. Design and optimization of the sensor is performed using numerical simulations to satisfy the competing requirements of high sensitivity, low structural non-linearity and high mechanical stability. Simulations are carried out to optimize the piezoresistor position, piezoresistor doping concentration and relative dimensions of the piezoresistor and the membrane. Results depict that sensor with a die size of 175 × 150 × 50 μm 3 results in an electrical sensitivity of 14.03 μA A -1 mmHg -1 . Finally, a set of design guidelines are outlined for optimizing the performance of three-terminal piezoresistor-based blood pressure sensors.
Ordered arrays of substrate supported gold nanodots are fabricated on c-Si as substrate. Electron beam lithography followed by DC sputter coating was used for the fabrication of ordered gold nanodots over a 1 × 1 cm 2 area on c-Si substrate. The fabricated ordered arrays of gold nanodots were characterised through the reflectance spectra. Reduction of 60.67% in reflectance was exhibited by ordered gold nanodots when compared with bare c-Si. For comparison, a random gold nanoparticle array of approximately same particle size was fabricated and the reflectance was compared with the ordered array. It was found that the reflectance of ordered array is 52.27% less than that of random array. This route is suitable for fabrication of large area ordered gold nanodots which has applications in photovoltaic industry.
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