[en] The effect of the volumetric flow, the temperature and the initial concentration of sucrose in the reaction of hydrolysis of sucrose by immobilized invertase were evaluated in the laboratory. Invertase was immobilized in 20 g of support of mesh size between 120 and 140. The maximum quantity of immobilized invertase obtained has been 0,130 mg/g of support at 220 min. The first experimental stage has consisted in the evaluation of the effect of the initial concentration of sucrose (1,0 and 1,5 mol/L), the volumetric flow (3,0 mL/min and 4,0 mL/min) and the temperature (45 degrees C and 50 degrees C). The effect of the above three variable has been statistically significant. The conversion has been favorable for a concentration of sucrose 1,0 mol/L, a volumetric flow of 3 mL/min and a temperature of 50 degrees C. The maximum conversion obtained has been 95,4 %. The second experimental stage has analyzed the effect of the initial concentration of sucrose (0,75 and 1,0 mol/L), the volumetric flow (2,5 mL/min and 3,0 mL/min) and the temperature (50 degrees C and 55 degrees C). The variable of volumetric flow and the interaction concentration of sucrose - temperature are found statistically significant. The conversion has been favorable for a volumetric flow of 2,5 mL/min, and it has been preferable to work at a temperature of 50 degrees C with an initial concentration of sucrose of 1,0 mol/L. The maximum conversion has been 94,8 %. The effect of the concentration was analyzed in the last experimental stage, it was found that the maximum conversion percentage was 95,0 % for a concentration of 1,1 mol/L, for a temperature of 50 degrees C and for a volumetric flow of 2,5 mL/min. (author)

[en] Two types of polymeric microparticle, Dynospheres and reprecipitated acid-hydrolysed nylon 6/6, and two methods of activating these particles with either tresyl chloride or carbonyldiimidazole (CDI) prior to covalent linkage of antibodies were investigated with a view towards their respective adoption for the preparation of general solid-phase reagents for immunoassay applications. Activation of each particle and coupling of antibodies was rapid irrespective of the activator. CDI proved to be the activator of choice since it was cheap, less hazardous, more efficient and less pH dependent than tresyl chloride. Both types of microparticle remain buoyant during the RIA incubation periods and form stable pellets after centrifugation. In second antibody applications immobilisation of the first antibody occurs with a short incubation period of 30 min. Nylon microparticles have a higher antibody-coupling capacity and are the particles of choice in both first and second antibody applications. However, the nylon microparticles possess marginally higher non-specific binding characteristics. (Auth.)

[en] Immobilized enzymes are replacing their soluble counter-parts in nearly every field of application. These enzyme modifications have evolved from a research curiosity into an entire branch of Biotechnology. An immobilization method for flavin containing oxidases and their use in flow injection system is described. An electrochemical detector for H/sub 2/O/sub 2/ is assembled which is used effectively for the determination of glucose using more common glucose oxidase and the simultaneous determination of sugars. The combination of oxidases with hydrolases have been used for the determination of maltose and starch. (author)

[en] Published in summary form only

[en] Covalent linkdage of IgG to Sepharose CL-4B with 1,1'carbonyldiimidazole has proved convenient for the production of solid-phase antibodies since preparation is rapid, simple, highly reproducible and relatively hazard free. The following study was designed to investigate the long term stability of solid-phase second antibody reagents prepared using this technique. It is therefore concluded that the covalent binding is relatively unstable; accordingly the authors recommend that the solid-phase second antibody reagent prepared as previously described should not be stored for prolonged periods

[en] Published in summary form only

[en] The geochemistry of natural phosphates of the apatite group indicates that these minerals have a high capacity for retention of uranium and its daughter products. ESCA spectroscopy shows that U and Ba (cf. Ra) are strongly absorbed on apatite. Large, reactive surfaces of apatite have been created by partial replacement of calcite and gypsum by phosphate solutions at the 300 ppm level. The same replacement has been achieved in impermeable calcite-rich, glacial tills. When typical waste effluents from a uranium mine are treated with such active phosphatic materials, radium-leach values are reduced to levels below 0.1 pCi/L, values in the range of ocean waters and high-quality fresh water

[en] Microbes play a primordial role in completing various elemental cycles namely carbon, nitrogen, sulfur, which are necessary for sustainability of planet Earth. This natural capability of microbes is employed to transform manmade compounds to their elemental forms. Redeployment of microbes for specific tasks needs a re-engineering of microbial metabolism to accelerate transformation. The most widely used approach is genetic modification but this approach has resulted into grievous failures due to inability of genetically modified organism to survive in natural environment. Consequently, development of new approach towards bioremediation was conceptualized, where desired metabolic capability were achieved using consortia of microorganisms having complementary metabolism. Of late, the potential of biofilm communities for bioremediation processes has been realized since it has many advantages over whole cells, used as biocatalysts. Naturally immobilized microbial biofilms exclude the necessity of cell-immobilization as biofilm cells are already embedded in self-produced exopolymers. Moreover, biofilm-mediated bioremediation offers a proficient and safer alternative to planktonic cells-mediated bioremediation because cells in a biofilm are more robust to toxic materials present in the waste as they are embedded in the matrix that provides a physical barrier. This presentation will highlight the importance of planktonic and sessile bacteria in bioremediation of a few nuclear waste compounds. (author)

[en] Some of the work carried out at our laboratories on the immobilisation of biocatalysts onto graft copolymers prepared by radiation induced procedures is reported. The graft copolymers used were based either on hydrophilic natural polymer (agar) or on hydrophobic (polyethylene) supports. The comonomers grafted branches include poly(hydroxyethyl methacrylate) and poly(hydroxyethyl methacrylate) crosslinked with trimethylpropane triacrylate (TMPTA). The suitability of these graft copolymers for immobilising α-chymotrypsin, glucose oxidase and trypsin was assessed by determining the amount of biocatalysts coupled to the support and its retention of activity. The Michaelis Menten constants (K_M) for some of the immobilised enzymes were determined. (author)

[en] Chitosan is a rather abundant material, which has been widely used in food industrial and bioengineering aspects, including in encapsulating active food ingredients, in enzyme immobilization, and as a carrier for drug delivery, due to its significant biological and chemical properties such as biodegradable, biocompatible, bioactive and polycationic. This review discussed preparation and applications of chitosan nanoparticles in the biomedical engineering field, namely as a drug delivery carrier for biopharmaceuticals. (author)