Effect of cadmium stress on antioxidative enzymes during the germination of Serbian spruce [Picea omorika (Pan..) Purkynĕ]

When considering the effect of heavy metals on trees generally and on forest ecosystems especially,  importance is given to their influence on seed germination in metal polluted soil. There is insufficient data on  this subject, especially when conifers are concerned. In this work, the influence of high cadmium  concentrations on percentage germination, specific activities and isoenzyme patterns of catalase (CAT),  superoxide dismutase (SOD), and peroxidase (POD) during the germination of Serbian spruce [Picea omorika (Pan..) Purkynĕ] was studied. Cadmium chloride concentrations of up to 0.1 mM did not cause an inhibition of germination, while 1 mM concentration inhibited germination and the activities of catalase, superoxide  dismutase and peroxidase. The isoenzyme profile of catalase and superoxide dismutase did not change at high cadmium concentrations, while peroxidase expression of basic peroxidase (B5) with pI value of 9.1 increased. This isoform of POD can play an important role in the early development of Serbian spruce and its defense mechanism against heavy metals.Key words: Seed germination, catalase, peroxidase, superoxide dismutase, heavy metals

The Enzyme Immobilization: Carriers and immobilization methods

Strategies based on the enzyme application are increasingly replacing the conventional chemical procedures because of their efficiency, quicker performance and environmental protection. However, natural enzymes can rarely be used in industry since their beneficial features can not endure the industrial conditions. Additional drawbacks of natural enzymes are their inhibition by reaction products and difficulty to be removed from the reaction mixture. The most promising technique to substantially improve the enzyme properties, such as activity, pH, thermal and organic-solvent stability, reusability and storage stability, in non-natural environments is by the enzyme immobilization. In this review we summarized different techniques used to immobilize enzymes to inert carriers. A wide variety of materials of both the organic and inorganic origin was used as carriers for the enzyme immobilization. We also summarized a class of new materials where the enzyme performance was enhanced by combining different classical materials and shaping in specific forms

Glucose oxidase variants with improved properities

Source: WO14173822A3 [EN] The technology provided herein relates to novel variants of microbial glucose oxidase with improved properties, more specifically to polypeptides having glucose oxidase activity as their major enzymatic activity; to nucleic acid molecules encoding said glucose oxidases; vectors and host cells containing the nucleic acids and methods for producing the glucose oxidase; compositions comprising said glucose oxidase; methods for the preparation and production of such enzymes; and to methods for using such enzymes for food and feed processing, for the measurement of free glucose in clinical samples and bioreactors, and the development of miniature biofuel cells

Immobilization of chemically modified horse radish peroxidase within activated alginate beads

Imobilizacija peroksidaze iz rena unutar alginatnih kuglica je poboljšana hemijskom modifikacijom enzima i polisaharidnih lanaca. Peroksidaza i alginat su oksidovani perjodatom i naknadno modifikovani etilendiaminom. Najveća specifična aktivnost od 0,43 U/ml gela i 81% vezane aktivnosti je dobijeno korišćenjem aminovane peroksidaze i alginata oksidovanog perjodatom. Imobilizovani enzim je zadržao 75% originalne aktivnosti nakon 2 dana inkubacije u 80% (v/v) dioksanu i imao je povećanu aktivnost pri baznim pH vrednostima u poređenju sa nativnim enzimom. Tokom višestruke upotrebe u šaržnom reaktoru za oksidaciju pirogalola imobilizovana peroksidaza je zadržala 75% početne aktivnosti.Immobilization of horseradish peroxidase (HRP) within alginate beads was enabled by chemical modification of the enzyme and polysaccharide chains. HRP and alginate were oxidized by periodate and subsequently modified with ethylenediamine. Highest specific activity of 0.43 U/ml of gel and 81% of bound enzyme activity was obtained using aminated HRP and alginate oxidized by periodate. Immobilized enzyme retained 75% of its original activity after 2 days of incubation in 80% (v/v) dioxane and had increased activity in basic solutions compared to native enzyme. During repeated use in batch reactor for pyrogallol oxidation immobilized peroxidase retained 75% of its original activity

Ultra-High-Throughput Screening Method for the Directed Evolution of Glucose Oxidase

Glucose oxidase (GOx) is used in many industrial processes that could benefit from improved versions of the enzyme. Some improvements like higher activity under physiological conditions and thermal stability could be useful for GOx applications in biosensors and biofuel cells. Directed evolution is one of the currently available methods to engineer improved GOx variants. Here, we describe an ultra-high-throughput screening system for sorting the best enzyme variants generated by directed evolution that incorporates several methodological refinements: flow cytometry, in vitro compartmentalization, yeast surface display, fluorescent labeling of the expressed enzyme, delivery of glucose substrate to the reaction mixture through the oil phase, and covalent labeling of the cells with fluorescein-tyramide. The method enables quantitative screening of gene libraries to identify clones with improved activity and it also allows cells to be selected based not only on the overall activity but also on the specific activity of the enzyme

Influence of methionine residue position on oxidative stability of glucose oxidase from Aspergillus niger

Glucose oxidase (GOx) is a promising candidate for construction of implantable miniature biofuel cells and biosensors for continuous glucose monitoring. The main drawback that limits current application of GOx in these devices is its low stability, especially sensitivity to reactive oxygen species. In order to address this problem, we performed saturation mutagenesis at all 11 methionine residues as their interaction with reactive oxygen species inactivates enzymes. For successful screening of these libraries a method based on yeast surface display (YSD) systems was developed. Mutations at methionine positions close to the GOx active site contributed the most to the oxidative stability, and combinations of the four best single mutations were tested. Combined mutants did not show higher stability or activity compared to the parental single mutants. To confirm oxidative stability of YSD expressed GOx mutants they were re-cloned in Pichia pastoris, purified and immobilized on macroporous copolymer. The additional kinetic analysis of immobilized GOx mutants confirmed that the best mutant with only one mutation close to the active site (M561S) has 2.5 times increased half-life in the presence of hydrogen peroxide compared to the wild-type variant

Immobilization of periodate oxidized invertase by adsorption on sepiolite

Periodate oxidized invertase was immobilized by adsorption on sepiolite. The obtained immobilized enzyme was more resistant to washing out by concentrated salt solution, and had an eight times higher half-life at 60ºC than adsorbed native invertase. In packed bed reactor 50 % conversion of 500 g/dm3 sucrose at 40ºC and a flow rate of 1 bv/h was achieved. The specific productivity of the immobilized invertase was 0.187 kg/dm3/h

Тбилисская Неделя N42

ყოველკვირეული გაზეთი სრული ტელეპროგრამით; Еженедельная газета с полной телепрограммо