| Sažetak | Ksilanaze su biokatalizatori koji pripadaju velikoj skupini enzima koje nazivamo hidrolazama. Vrlo su značajne u industrijskoj primjeni, a njihova upotreba je danas u sve većem porastu. Njihov značaj prepoznat je u industriji celuloze i papira u postupcima izbjeljivanja celulozne mase što rezultira smanjenom upotrebom opasnih kemikalija. Osim u industriji papira, ksilanaze su važne i u prehrambenoj, kemijskoj, farmaceutskoj i tekstilnoj industriji. Prisutnost ksilanaza u reakcijskom mediju, kao i ostalih enzima kao katalizatora, omogućuje odvijanje (bio)kemijskih reakcija u blagim uvjetima, a uz to su sami enzimi obnovljivi i biorazgradivi. Zbog tih prednosti se može reći da su enzimi, a ujedno i ksilanaze ekološki prihvatljivi, pogotovo u usporedbi s kemijskim katalizatorima koje sve češće zamjenjuju i čiju upotrebu smanjuju. Izvor ksilanaza mogu biti gljive, bakterije, kvasci te razne životinje poput puževa, rakova i kukaca, pri čemu su glavni komercijalni izvor ksilanaza nitaste gljive. Najčešće se ksilanaze proizvode iz mikroorganizama submerznom fermentacijom, ali se sve češće kao tehnika proizvodnje enzima koristi i fermentacija na čvrstim nosačima. Proizvodnjom ksilanaza iz različitih izvora, različitim procesima i pri različitim uvjetima dobivaju se ksilanaze različitih svojstava i aktivnosti. Kako bi se odredila svojstva enzima i posljedično omogućila njegova industrijska upotreba, potrebno je provesti karakterizaciju enzima. Na aktivnost enzima utječu mnogi čimbenici kao što su temperatura, pH-vrijednost, vrsta supstrata korištena pri uzgoju mikroorganizama iz kojih se enzim dobiva, kemijsko djelovanje prisutnih tvari itd. Cilj ovog rada bio je karakterizirati sirovi ekstrakt enzima endo-1,4-ksilanaza proizvedenog fermentacijom Trametes versicolor na čvrstim nosačima. Kako je jedno od najvažnijih svojstava enzima njegova aktivnost, upravo je određivanje aktivnosti enzima endo-1,4-ksilanaze bio početni korak u njegovoj karakterizaciji. Osim toga određeni su temperaturni i pH optimum, temperaturna stabilnost te utjecaji određenih metalnih iona, organskih otapala, reagensa i supstrata na aktivnost enzima endo-1,4-ksilanaza. |
| Sažetak (engleski) | Xylanases are biocatalysts that belong to a large group of enzymes commonly known as hydrolases. Their application in industry is significant and is rapidly growing. Their significance was recognized in the pulp and paper industry in the process of biobleaching of kraft pulp which reduces the use of toxic chemicals. Moreover, xylanases are also important in the chemical, textile, pharmaceutical, and food industries. The presence of xylanases in the reaction medium, like that of other enzymes, allows (bio)chemical reactions to take place under mild conditions. They are also renewable and biodegradable. Due to these advantages, it could be said that enzymes, as well as xylanases, are environmentally friendly, especially when compared to chemical catalysts that they more and more replace or reduce the use of. Sources of xylanases are fungi, bacteria, yeasts, and a variety of animals such as snails, crabs, and bugs from which the main commercial source of xylanases are filamentous fungi. The most common production process of xylanases is submerged fermentation, although solid-state fermentation is also being used widely. Xylanases are produced from different sources, with different processes, and under different conditions, resulting with different properties and activities. In order to determine the properties of an enzyme and consequently its use in industry, it is necessary to conduct the characterization of the enzyme. Many factors affect the enzyme activity such as temperature, pH value, type of substrate used for cultivation of microorganisms from which enzymes are obtained, chemical effect of present substances, and so on. The aim of this work was to characterize the crude extract of endo-1,4-xylanase enzyme produced by solid-state fermentation of Trametes versicolor. Since one of the most important properties of enzymes is their activity, estimation of activity of the endo-1,4-xylanase enzyme was the first step of its characterization. Besides this, temperature and pH optimum, temperature stability, and the effects of certain metal ions, organic solvents, reagents, and substrate on the activity of endo-1,4-xylanase are determined in this work. |
