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The object of the study was to investigate the process conditions relevant for the pentyl octanoate production with the lipase from Candida rugosa immobilized on Sepabeads EC-EP carrier. This is an epoxide-containing commercial polymethacrylic carrier with suitable characteristics for enzyme immobilization. The immobilized lipase suitable for pentyl octanoate synthesis has been prepared by a direct lipase binding to polymers via their epoxide groups. The enzymatic activity was determined by both hydrolysis of olive oil in an aqueous system and esterification of n-pentanol with octanoic acid in a low aqueous system. The influence of several important reaction parameters such as temperature, initial water content, initial substrate molar ratio, enzyme loading and time of adding of molecular sieves in the system is carefully analyzed by means of an experimental design. Production of the ester was optimized and an ester production response equation was obtained, making it possible to predict ester yields from known values of the five main factors. Almost complete conversion ( gt 99%) of the substrate to ester could be realized, using lipase loading as low as 37 mg/g dry support and in a relatively short time (24 h) at 45ºC, when high initial substrate molar ratio of 2.2 is used. U radu su ispitani uticaji procesnih parametara na sintezu pentil-oktanoata pomoću lipaze iz Candida rugosa imobilisane na komercijalni polimetakrilatni nosač (Sepabeads EC-EP). U radu je primenjena metoda imobilizacije enzima koja se zasniva na direktnom vezivanju enzima za nosač preko epoksidne grupe polimera. Aktivnost imobilisanog enzima ispitana je u vodenom sistemu na model reakciji hidrolize maslinovog ulja kao i u nevodenom sistemu na modelu sinteze pentil-oktanoata u izooktanu. Ispitani su uticaji pet procesnih faktora na enzimsku sintezu datog estra primenom metode planiranih eksperimenata i metodologije odzivnih površina i to sadržaja vode, temperature, mase vezanog enzima na nosaču, početnog molarnog odnosa reaktanata i trenutka dodavanja molekulskih sita u sistem. Sinteza estara je optimizovana, izvršena je ocena značajnosti parametara i utvrđen je adekvatan matematički model na osnovu koga se može predvideti ponašanje sistema (prinos estara) u funkciji navedenih faktora.

Biodiesel is an alternative fuel for diesel engine that is environmentally acceptable. Conventionally, biodiesel is produced by transesterification of triglycerides and short alcohols in the presence of an acid or an alkaline catalyst. There are several problems associated with this kind of production that can be resolved by using lipase as the biocatalyst. The aim of the present work was to investigate novel acyl acceptors for biodiesel production. 2-Propanol and n-butanol have a less negative effect on lipase stability, and they also improve low temperature properties of the fuel. However, excess alcohol leads to inactivation of the enzyme, and glycerol, a major byproduct, can block the immobilized enzyme, resulting in low enzymatic activity. This problem was solved by using methyl acetate as acyl acceptor. Triacetylglycerol is produced instead of glycerol, and it has no negative effect on the activity of the lipase. U ovom radu ispitana je mogućnost primene različitih acil akceptora kao polaznih reaktanata umesto metanola u sintezi biodizela u cilju smanjenja inhibicije enzima, povećanja njegove stabilnosti i mogućnosti značajnog pojednostavljivanja izvođenja procesa. Prvo je ispitana mogućnost korišćenja različitih alkohola: 2-propanol i n-butanol koji imaju manji uticaj na denaturaciju enzima. Osim toga, primenom ovih alkohola dobija se gorivo boljeg kvaliteta, pošto se sa povećanjem broja ugljenikovih atoma povećava oktanski broj, temperatura paljenja, kao i sadržaj toplote. Drugi deo istraživanja bio je orijentisan ka ispitivanju mogućnosti korišćenja metilacetata kao pogodnog nukleofila. Za razliku od alkohola, primenom ovog acil akceptora omogućen je jednostepeni postupak sinteze biodizela, što značajno smanjuje vreme trajanja reakcije, kao i kompleksnost iste. Takođe, primenom metilacetata povećava se stabilnost biokatalizatora, što omogućava višekratnu upotrebu. Naime, u reakciji sa metilacetatom kao nusprodukt se ne stvara glicerol već triacetilglicerol, koji nema negativan efekat na stabilnost lipaze.