Uticaj veličine čestica polianilina na imobilizaciju alfa-amilaze

In this paper polyaniline was synthesized by interfacial polymerization of monomer aniline in a water/chloroform system. Four fractions of polyaniline microparticles (in the range of 90-800 μm) are used as a support for immobilizing the alpha-amylase from Bacillus licheniformis. The equilibrium amount of enzyme, amount of washed enzyme, adsorption yield , the activity of immobilized enzyme and activity yield were studied. It was found that the maximum amount of the adsorbed enzyme was to a particle size of 90-160 μm, but at the same time from these particles enzymes were desorbed to larger extent during washing. However, it has been shown that as the particle size increased the activity of the immobilized enzyme decreased with the exception of the particle sizes of 160-315 μm and the activity of immobilized enzyme was not dependent on adsorption yield. The highest average activity yield of adsorbed α-amylase, 4,62% was at polyanilne particle size of 160-315 μm .U ovom radu sintetisane su čestice polianilina postupkom polimerizacije anilina na granici dve faze voda/hloroform. Četiri frakcije dobijenih mikročestica polianilina u opsegu od 90-800 μm korišćene su kao nosač za imobilizaciju enzima alfa-amilaze iz Bacillus licheniformis. Određena je ravnotežna masa enzima, masa ispranog enzima, prinos mase, aktivnost dobijenog biokatalizatorskog sistema kao i prinos aktivnosti. Utvrđeno je da se najveća masa enzima veže za čestice veličine 90-160 µm, ali da se sa ovih čestica i najviše enzima desorbuje tokom ispiranja. Međutim, pokazano je da se sa povećanjem veličine čestica smanjuje aktivnost imobilisanog enzima sa izuzetkom čestica dimenzija od 160-315 μm, pri čemu aktivnost imobilizata ne zavisi od prinosa mase. Prinos aktivnosti imobilisane α-amilaze u odnosu na aktivnost slobodnog enzima koji se vezao za nosač prosečno je najveći kod čestica veličine 160-315 μm

Enhanced anaerobic digestion of combined wastewater sludges through solubilization of waste activated sludge

Pilot-scale research on enhancement of anaerobic co-digestion of combined primary and secondary sludges was performed, using a low-level alkaline solubilization process for the secondary sludge. Research was conducted in two phases: the first phase investigated chemical dosages of calcium hydroxide and sodium hydroxide and mechanical mixing times for waste activated sludge (WAS) solubilization; the second, pilot-scale phase monitored the performance of anaerobic digestion, using mixtures of solubilized WAS and primary sludge as a feed. The first phase results showed that solubilization of WAS can be effectively performed using both chemicals separately. However, for the same chemical dosage and anoxic mixing time, sodium hydroxide was more effective in WAS solubilization. Performance of three pilot-scale units, one control and two experimental (expCa(OH)₂ and exp NaOH) units was monitored in the second phase. Each anaerobic unit was 160 L in liquid volume and operated as a single-stage, high-rate system; operating temperature was 35°C. The ratio of WAS to primary sludge was 65/35 by volume; a chemical dose of 15 meq/L and anoxic mixing time of 5 hours was applied for WAS solubilization. All parameters were kept constant through the whole study except solids retention time (SRT); SRT was gradually decreased from 25 to 10 days, in 5 day increments, i.e. 4 runs. The second phase results indicated better digester performance of both experimental units, with exp NaOH outperforming lime. Volatile mass reduction was independent of SRT and the best overall VSS reduction was observed in the exp NaOHunit. However, the improvement in overall VSS reduction was attributed to the solubilization process itself, and not necessarily to better digester performance per se. The addition of sodium hydroxide to the WAS allowed for a decrease of SRT from 25to 10 days, without losing VSS reduction efficiency. Carbon removal (in terms of total and soluble COD removal) actually increased with a decrease in SRT and the highest carbon removal was achieved in the exp NaOHunit. Better carbon removal was also reflected in a higher methane content of the gas. The effect of solubilizing the WAS, prior to digestion, was also reflected in a higher unit gas production (L/kg VSS reduced) in both experimental units. Results obtained in the second phase proved that WAS pretreatment enhanced volatile mass reduction, total and soluble COD removal, gas quality and unit gas production in the anaerobic digestion of mixed wastewater sludges. Also, there was no major effect on effluent quality in terms of nitrogen, phosphorus (except for lower soluble phosphorus in the exp Ca(OH)₂ unit), VFA and TOC concentrations. Based on the results obtained in this study, it is strongly recommended that a full scale evaluation be undertaken of combining pretreated WAS with primary sludge in a high-rate, single-stage anaerobic digester and implement a complete cost-benefit analysis of such.Applied Science, Faculty ofCivil Engineering, Department ofGraduat

Immobilized lipases as practical catalysts

Attractive features of lipase systems include versatility, substrate selectivity, regioselectivity, enantioselectivity and catalysis at ambient temperatures and pressures. To fully exploit the technical and economical advantages of lipases, it is recommended to use them in an immobilized form to reduce the cost and the poor stability of the free lipase. This paper summarizes various methods of lipases immobilization including covalent attachment to or adsorption on solid supports, encapsulation and entrapment within the membrane and in polymeric matrices. The effects of immobilization conditions on lipase properties and stability of biocatalysts are considered. Applications of immobilized lipases in the feasible reaction system as well as probable future trends in lipase catalyzed process are discussed.Lipaze su enzimi od velikog potencijalnog praktičnog značaja zbog osobine da selektivno katalizuju veliki broj reakcija pod blagim uslovima i bez primene kofaktora. Savremeni pristup primeni ovih enzima u industrijskim uslovima predstavqa primena imobilisanih enzima, čime se povećava njihova stabilnost i omogućuje primena u kontinualnim sistemima. U radu je dat pregled različitih metoda i nosača za imobilizaciju lipaza uključujući kovalentnu imobilizaciju adsorpciju, mikroinkapsulaciju i zarobljavanje enzima unutar polimerne matrice i u pore membrane, pri čemu je ukazano na prednosti i nedostatke svakog od imobilisanih sistema. Diskutovani su uticaji uslova imobilizacije i prirode nosača na osobine i stabilnost biokatalizatora. Takođe su razmatrane mogućnosti primene imobilisanih lipaza u reakcijama od praktičnog značaja kao i razvoj novih imobilisanih sistema

Optimization of esterification activity of lipase from Candida rugosa immobilized using microwave irradiation

Lipases are very efficient biocatalysts with wide application in synthesis of important ingredients of food, cosmetics and pharmaceutical products, due to their capacity to catalyze both, ester synthesis and ester hydrolysis. The preparation of stable and active immobilized derivatives of lipases is necessity for their application in industrial enzymatic processes. In this work, the optimization of lipase from C. rugosa immobilization by microwave irradiation was performed, since it was previously reported that immobilization process can be drastically accelerated by means of microwave irradiation, even resulting with slight increase of lipase activity. Eupergit®, commercial support with active epoxy groups, was used as immobilization support. In first stage of our study, the immobilization time and ionic strength of immobilization buffer were optimized. It was found out that the highest immobilized activity can be achieved at high ionic strengths (1 M buffer) after 3 min, while further increase of immobilization time led to decrease of lipase activity. Then, the immobilized derivative obtained at optimum conditions was applied in synthesis of amyl isobutyrate in organic solvent. Key reaction factors (temperature, water concentration, immobilized lipase concentration, and substrate molar ratio) were optimized using response surface methodology. The substrate conversion higher above 85% was achieved in our study. The statistical analysis revealed that each of analyzed factors had significant effect on yield of ester, with initial enzyme concentration and substrate molar ratio being the most prominent factors. The second-order regression model that describes the effect of all four factors on substrate conversion was established. The optimum values of factors were: temperature 50°C, initial immobilized enzyme concentration 220 mg ml-1, added water concentration 0.1% (v/v), and molar ratio acid/alcohol 2.5.Lipaze su enzimi koji imaju široku primenu u prehrambenoj, kozmetičkoj i farmaceutskoj industriji. U industrijskoj praksi primenjuju se imobilisane lipaze jer se imobilizacijom povećava njihova stabilnost i ekonomičnost enzimskih postupaka. U ovom radu optimizovana je imobilizacija lipaze iz C. rugosa na komercijalni nosač Eupergit® pomoću mikrotalasnog zračenja. Vreme izlaganja mikrotalasima i molaritet korišćenog pufera optimizovani su sa ciljem dobijanja imobilizata maksimalne aktivnosti. Radi optimizovanja reakcije sinteze amil-izobutirata, pomoću centralnog kompozitnog rotatabilnog plana ispitan je uticaj četiri reakciona faktora. Ustanovljeno je da su optimalni uslovi sinteze estra temperatura 50°C, početna koncentracija imobilisanog enzima 220 mg ml-1, koncentracija dodate vode 0,1% i molarni odnos supstrata 2,5

Lipase catalyzed synthesis of flavor esters in non-aqueous media: Optimization of the yield of pentyl 2-methylpropanoate by statistical analysis

In this study, the synthesis of pentyl 2-methylpropanoate employing a commercial lipase from Candida rugosa was investigated, the emphasis being placed on analyzing the effects of various process conditions on the yield of ester. The response surface methodology (RSM) and five-level-five-factor central composite rotatable design (CCRD) were used to evaluate the effects of variables, namely the initial water content, 0.0–2.0 % (w/v), the reaction temperature, 35–75 °C, the enzyme concentration, 1.0–5.0 g dm-3, the acid/alcohol mole ratio, 1:2–5:2, and the reaction time, 4–48 h, on the yield (%) of ester. The production of pentyl 2-methylpropanoate was optimized and an ester yield response equation was obtained, enabling the prediction of ester yields from known values of the five main factors. It seems that the enzyme concentration, reaction time and acid/alcohol mole ratio predominantly determine the conversion process, while the amount of added water amount had no significant influence on the ester yield. Conversion of around 92 % of the substrate to ester could be realized using a concentration of lipase as low as 4.0 g dm-3 and in a relatively short time (26 h) at 35 °C, when a high substrate mole ratio of 2.5 was used

The content and composition of humus in pseudogleys of slopes and plains in South Macva and Pocerina

The scope of this paper was to examine the influence of two subtypes of pseudogley soil (of planes and of slopes) and three different land uses (forest, grassland and arable land) on the content and composition of humus in south Mačva and Pocerina. The humus content was determined by dichromate method, and humus components were measured using the method proposed by Kononova and Belcikova. The studied soils are mostly characterized by low humus content. Humus content is significantly higher in pseudogleys of plains compared to pseudogleys of slopes. Pseudogleys under grass and crops have significantly lower content of humus compared to the pseudogleys under forest. Important characteristic of humus composition of surface horizon is dominant portion of fulvic over humic acids. Pseudogleys of plains have statistically significant higher amount of humic acids. The composition of humus is significantly different in pseudogley under forest compared to pseudogleys under grass and crops: it has more fulvic acids, less humin, and lower Ch:Cf ratio. Changes in pseudogley land use have produced better humus quality.Cilj ovog rada je ispitivanje uticaja dva podtipa pseudogleja (ravničarskog i obronačnog) i tri načina korišćenja (šuma, travnjak, njiva) na sadržaj i grupno-frakcioni sastav humusa na području južne Mačve i Pocerine. Ispitivana zemljišta generalno karakteriše uglavnom nizak sadržaj humusa. Statistički značajno je sadržaj humusa veći u ravničarskom podtipu pseudogleja u poređenju sa obronačnim. U pseudogleju pod travnom vegetacijom i na obradivim površinama došlo je do statistički značajnog smanjenja sadržaja humusa u poređenju sa pseudoglejom pod šumom. Bitna karakteristika grupno-frakcionog sastava humusa površinskog horizonta je dominacija fulvo nad huminskim kiselinama. Ravničarski pseudoglej sadrži statistički značajno više huminskih kiselina. Sastav humusa se značajno razlikuje u pseudogleju pod šumom u poređenju sa pseudoglejom pod travom i njivom: sadrži više fulvo kiselina, a manje humina i ima uži Ch:Cf odnos. Promena načina korišćenja pseudogleja dovela je do poboljšanja osobina humusa, odnosno donekle dovela do stabilizacije humusa i umanjila njegove inače veoma loše osobine

Тбилисская Неделя N42

ყოველკვირეული გაზეთი სრული ტელეპროგრამით; Еженедельная газета с полной телепрограммо

Immobilization of lipase from Candida rugosa into copolymer hydrogels of poly(N-isopropylacrylamide-co-itaconic acid) synthesized in the presence of surfactants

To overcome the problems of free enzyme application as catalysts in chemical reactions, i.e., high costs of isolation and purification processes, high sensitivity to process conditions, insufficient enzyme stability etc., different immobilization techniques need to be used. Immobilization to/within solid support improves enzyme stability decreasing its denaturation. This paper deals with hydrogels of N-isopropylacrylamide and itaconic acid with incorporated nonionic surfactants (Triton X-100, Brij 30 and Tween 80) synthesized in distilled water at room temperature by free radical polymerization. These hydrogels were used as supports for immobilization of enzyme, lipase from Candida rugosa by post-entrapment method. The aim was to investigate the effect of the non-ionic surfactants on the lipase binding capacity, as well as on its hydrolytic activity. In order to characterize the obtained hydrogels, FT-IR analysis has been performed. Further, the swelling behaviour of these samples in buffer solution of pH 6.80 has been investigated. The dynamic-mechanical properties of hydrogels have been studied, too. The immobilized lipase showed somewhat reduced hydrolytic activity, compared to the activity of free lipase as well as in comparison to the lipase immobilized to the reference sample (sample synthesized under the same polymerization conditions, but in the absence of surfactants). It was concluded that the addition of surfactants increased the hydrogel mesh size. The surfactant addition did not affect the dynamic-mechanical properties of the investigated hydrogels. The largest percentage of specific activity and yield of activity were presented by the reference sample, too. It is obvious that the absence of surfactants charged groups has no influence on the lipase binding capacity, and the obtained activity yields are to be expected.U radu je ispitana imobilizacija lipaze iz Candida rugosa u hidrogel poli(N-izopropilakrilamid-ko-itakonska kiselina) sintetisane u prisustvu nejonskih površinski aktivnih materija. Pri sintezi je varirana vrsta i sadržaj površinski aktivnih materija. Ispitana su mehanička svojstva sintetisanih hidrogelova i urađena je FT-IR analiza. Imobilizacija lipaze je izvedena bubrenjem prethodno sintetisanih hidrogelova u rastvoru lipaze, a zatim je ispitan uticaj dodatka površinski aktivnih materija pri sintezi nosača na kapacitet uklapanja lipaze u hidrogel i na aktivnost tako uklopljene lipaze. Imobilisana lipaza iz Candida rugosa je pokazala umanjenu hidrolitičku aktivnost, kako u odnosu na aktivnost slobodne lipaze, što je i očekivano, tako i u odnosu na aktivnost lipaze imobilisane u referentni hidrogel, sintetisan bez prisustva površinski aktivnih materija