enzimska lipofilizacija vitamina C linolnom kiselinom - određivanje antioksidativnih i difuzionih svojstava L-askorbil-linolata

Lipophilic derivatives of vitamin C are additives with antioxidant properties, attractive for application in food, cosmetics and pharmaceutics. They could be synthesized in lipase-catalyzed processes by using various acyl donors. Hereby, we present application of linoleic acid, which is polyunsaturated fatty acid essential in human nutrition, for esterification of vitamin C catalyzed by immobilized enzyme preparation Novozym® 435 in acetone. Highest specific ester yield, 9.7 mmol/g of immobilized lipase, was accomplished with 0.15 M of vitamin C, 0.6 M of linoleic acid, 3 g/l of enzyme and 0.07% (v/v) of water, at 60°C. NMR analyses of purified product proved that synthesized molecule was identical to 6-O-ascorbyl linoleate. Capacity of ester for scavenging 2,2-diphenyl-1-picrylhydrazyl radicals was two times higher comparing to parent molecule, vitamin C. Its diffusion coefficient, determined using Franz cell and cellulose acetate membrane, was 40% higher than palmitate and 62% higher than oleate. Obtained results showed that L-ascorbyl linoleate could be successfully synthesized in biocatalyzed processes. Furthermore, it was demonstrated that it possess high potential for application in different lipophilic products due to its liposolubility, high antioxidant efficiency and good diffusion properties.Lipofilni derivati vitamina C su aditivi sa antioksidativnim dejstvom pogodni za primenu u prehrambenim, kozmetičkim i farmaceutskim proizvodima. Mogu biti sintetisani u procesima katalizovanim lipazama korišćenjem različitih acil-donora. U ovom radu, opisana je primena linolne kiseline, polinezasićene masne kiseline esencijalne u ljudskoj ishrani, u esterifikaciji vitamina C katalizovanoj imobilisanim enzimskim preparatom Novozym® 435 u acetonu. Najviši specifični prinos estra od 9,7 mmol/g imobilisane lipaze, ostvaren je sa 0,15 M vitamina C, 0,6 M linolne kiseline, 3 g/l enzima i 0,07 zapr. % vode, na 60°C. NMR analize prečišćenog proizvoda dokazale su da je sintetisani molekul identičan 6-O-askorbil-linolatu. Kapacitet estra za vezivanje 2,2- difenil-1-pikrilhidrazil radikala bio je dva puta viši u odnosu na sam vitamin C. Njegov koeficijent difuzije, određen korišćenjem Franz-ove ćelije i celuloza-acetatne membrane, bio je za 40% viši u odnosu na palmitat i za 62% u odnosu na oleat. Ostvareni rezultati pokazali su da L-askorbil-linolat može uspešno biti sintetisan u biokatalizovanom procesu. Pored toga, dokazano je da ovaj estar poseduje značajan potencijal za primenu u različitim lipofilnim proizvodima zbog svoje liposolubilnosti, snažnog antioksidativnog dejstva i pogodnih difuzionih karakteristika

Characterization of hydrothermaly synthesized zirconia nanopowders

In this paper,a hydrothermal method for synthesis of zirconia nanopowders: pure and with incorporated Si4+ions is presented. Zirconyl chloride and tetraethyl orthosilicate were used as precursors. As prepared powders were annealed at 600 °C and their structural (XRD), morphological (TEM) and textural (BET method) properties were obtained.It has been shown that by using hydrothermal synthesis method pure monoclinic ZrO2highly crystalline powder can be obtainedwithcrystallites of about 25nm. Incorporation of Si4+ions induced stabilization of tetragonal crystalline phase at room temperature, decreasing particle sizes to about 3-6 nm and increasing specific surface area of nanopowders.Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 201

Zirconium dioxide nanopowders with incorporated Si4+ ions as efficient photocatalyst for degradation of trichlorophenol using simulated solar light.

We present a hydrothermal method for synthesis of zirconia nanopowders: pure and with incorporated Si4+ ions. Zirconyl chloride and tetraethyl orthosilicate were used as precursors. As prepared powders were annealed at 600 degrees C and characterized using structural (XRD), morphological (SEM and TEM) and optical techniques (UV/vis DR, FTIR and photoluminescence spectroscopy). Their textural properties (BET method) and photocatalytic activity toward degradation of model compounds (tricholophenol and Rhodamine B) using simmulated solar light were obtained. We showed that by using hydrothermal synthesis method pure monoclinic ZrO2 highly crystalline powder can be obtained. Incorporation of Si4+ ions induced stabilization of tetragonal crystalline phase at room temperature and decreasing of particle sizes. Incorporation of Si4+ ions in zirconia matrix also resulted in increase of specific area of nanopowders. FTIR measurements were used as proof for existence of Zr-O-Si bond. Effective band gap of zirconia powders was reduced from 5 (pure ZrO2) to 3.8 eV for samples with Si4+ ions. All zirconia powders showed significant photocatalytic activity regarding degradation of triclorophenol and no activity regarding RB (Rhodamine B dye). Photocatalytic activity of zirconia was increased by incorporation of Si ions in the host matrix. The source of this observation is discussed correlating all obtained properties of pure and Si-incorporated nanopowders. Optimization of synthesis parameters and composition of zirconia samples obviously can lead to their photocatalytic activity comparable to Degussa TiO2 powder, famous and commercial photocatalyst. (C) 2016 Elsevier B.V. All rights reserved

Stabilization of immobilized lipase from Candida rugosa by amino acid treatment

Lipaze su enzimi koji imaju široku primenu u prehrambenoj, kozmetičkoj i farmaceutskoj industriji. U industrijskoj praksi primenjuju se imobilisane lipaze, s obzirom da se imobilizacijom povećava stabilnost samog enzima, ali i ekonomičnost enzimskog postupaka proizvodnje. Kao nosači za imobilizaciju najčešće se koriste sintetski ili prirodni polimeri bogati funkcionalnim grupama preko kojih se enzim može vezati. U nekim slučajevima, neophodna je prethodna modifikacija nosača radi uvođenja funkcionalnih grupa. U ovom radu lipaza je imobilisana na modifikovanu jonoizmenjivačku smolu, Purolite® A109, koja je u osnovi kopolimer stirena i divinilbenzena, a koja na površini poseduje primarnu amino grupu. Modifikacija nosača izvršena je sa ciljem da se primarne amino grupe nosača prevedu u epoksi grupe, čime se dobija nosač pogodan za kovalentnu imobilizaciju lipaze. Kovalentna imobilizacija je do sada pokazala najbolje rezultate kada su u pitanju aktivnost i stabilnost dobijenih imobilizata1,2. Dobijeni imobilizati tretirani su aminokiselinama da bi se ispitalo njihovo dejstvo na stabilnost i aktivnost imobilisane lipaze. Efekat tretmana aminokiselinama na stabilnost imobilisane lipaze praćen je ispitivanjem aktivnosti netretiranog i tretiranih imobilizata tokom inkubacije na 65 °C.Lipases are important catalysts in pharmaceutical, cosmetics and food industry. On industrial scale, lipases are used only in immobilized form. Majority of enzymes lose part of its initial activity during immobilization process, but activity also decreases throughout storage and usage of immobilized lipase. Therefore, adequate immobilization supports are prerequisite for successful application of immobilized enzyme. When it comes to epoxy supports, after immobilization unreacted epoxy groups can interact with side chains of protein, which could result in additional enzyme activity loss. Blocking of epoxy groups is usually performed with 2- mercaptoethanol or ethylenediamine. In this study, treatment of immobilized lipase with different amino acids (glycine, phenylalanine, arginine and aspartic acid) was performed. Phenylalanine and glycine exhibited positive effect on stabilization of immobilized lipase, so this treatment should be examined more thoroughly. On the other hand, arginine and aspartic acid showed no effect on stabilization of immobilized lipase

Effective valorisation of barley bran for simultaneous cellulase and beta-amylase production by Paenibacillus chitinolyticus CKS1: Statistical optimization and enzymes application

The agricultural raw industry generates large amounts of annually by-products that create disposal problems. Hitherto, there have been no reported papers about the simultaneous production of cellulase and beta-amylase from these raw materials using Paenibacillus sp. that would reduce the costs. Thus, in this paper simultaneous cellulase (CMC-ase and avicelase) and beta-amylase production using barley bran and the application of the natural isolate Paenibacillus chitinolyticus CKS1 and potential enzymes in the hydrolysis process was studied. Response surface methodology was used to obtain the maximum enzyme activity (CMC-ase 0.405 U mL(-1), avicelase 0.433 U mL(-1) and beta-amylase 1.594U mL(-1)). Scanning electron microscopy showed degradation of the lignocellulosic-starch structure of barley bran after fermentation. The CKS1 bacterial supernatant, which contains cellulases and beta-amylase, could hydrolyze cotton fibres and barley bran, respectively. The main products after enzymatic hydrolysis of cotton fibres and barley bran, glucose (0.117 (-1)(g gmat)) and maltose (0.347 (-1)(g gmat)), were quantified by high performance liquid chromatography (HPLC). The produced enzymes could be used for hydrolysis of cotton fabric and barley bran to glucose and maltose, respectively. Application of simultaneous enzymes production using an agricultural by-product is economically and environmentally accepted and moreover, valuable biotechnological products, such as glucose and maltose, were obtained in this investigation

Enzymatic synthesis and application of fatty acid ascorbyl esters

Fatty acid ascorbyl esters are liposoluble substances that possess good antioxidative properties. These compounds could be synthesized by using various acyl donors for acylation of vitamin C in reaction catalyzed by chemical means or lipases. Enzymatic process is preferred since it is regioselective, performed under mild reaction conditions, with the obtained product being environmentally friendly. Polar organic solvents, ionic liquids, and supercritical fluids has been successfully used as a reaction medium, since commonly used solvents with high Log P values are inapplicable due to ascorbic acid high polarity. Acylation of vitamin C using fatty acids, their methyl-, ethyl-, and vinyl esters, as well as triglycerides has been performed, whereas application of the activated acyl donors enabled higher molar conversions. In each case, majority of authors reported that using excessive amount of the acyl donor had positive effect on yield of product. Furthermore, several strategies have been employed for shifting the equilibrium towards the product by water content control. These include adjusting the initial water activity by pre-equilibration of reaction mixture, enzyme preparation with water vapor of saturated salt solutions, and the removal of formed water by the addition of molecular sieves or salt hydrate pairs. The aim of this article is to provide a brief overview of the procedures described so far for the lipase-catalyzed synthesis of fatty acid ascorbyl esters with emphasis on the potential application in food, cosmetics, and pharmaceutics. Furthermore, it has been pointed out that the main obstacles for process commercialization are long reaction times, lack of adequate purification methods, and high costs of lipases. Thus, future challenges in this area are testing new catalysts, developing continuous processes for esters production, finding cheaper acyl donors and reaction mediums, as well as identifying standard procedures for purification of products which will not require consumption of large amounts of non-biocompatible organic solvents

Lignocellulosic waste material as substrate for Avicelase production by a new strain of Paenibacillus chitinolyticus CKS1

A novel strain of Paenibacillus chitinolyticus CKS1 was isolated from forest soil and identified as a potent cellulase producer. The strain was able to grow on various commercial substrates including microcrystalline cellulose (Avicel), carboxymethylcellulose (CMC), and cellobiose but also on lignocellulosic waste material such as medicinal herbs waste and sawdust. On all these substrates the strain produced cellulase composed of two subunits (similar to 70 and similar to 45 kDa) that was active on CMC, Avicel and filter paper. The maximal Avicelase activity (1.94 U/ml) was reached in a medium that contained 0.1% (w/v) of medicinal herbs waste, 3 g l(-1) of yeast extract and 5.0 g l(-1) of casein hydrolysate in 0.1 M phosphate buffer pH 7, after 48 h of incubation at 30 degrees C. The Avicelase performed optimally at 80 degrees C and at pH 4.8. Addition of K+ increased the Avicelase activity almost three fold and the enzyme retained 48.39% of the initial activity after 60 min. The product of Avicel and CMC hydrolysis was glucose with traces of other soluble sugars, indicating that the crude cellulase produced on waste material using the novel P. chitinolyticus strain CKS 1 could be used in eco-friendly processes of cellulose bioconversion, such as enzymatic saccharification of lignocellulosic materials in processes performed under acidophilic conditions and high temperatures