| Abstract [eng] |
Lipases are enzymes whose natural function is to hydrolyze triglycerides into diglycerides, monoglycerides, fatty acids and glycerol. However, under certain conditions, they are also able to catalyze synthetic reactions such as esterification and transesterification in non-aqueous media. As a result, lipases have been used in various industrial processes for over two decades. Various filamentous fungi, including Aspergillus spp., are recognized as the best lipase producers since their produced lipases are extracellular, with wide range of substrate specificity and high stability. The main goal of this study was to find a fast, inexpensive and efficient immobilisation method for Aspergillus sp. lipase that the acquired enzymatic preparation had the highest specific activity in organic media. The selected immobilisation methods were optimised and the acquired enzymatic preparations were compared according to their specific activity in organic media, thermostability, efficiency for natural fragrance ester 2-phenylethylbutanoate enzymatic synthesis and reusability. Aspergillus sp. lipase was immobilised by three different methods: acquiring CLEA by cross-linking enzyme aggregates, covalently immobilising on magnetite (Fe3O4) nanoparticle clusters and adsorbing on a support which was acquired by pyrolysing sugar industry waste. Of all the acquired and optimised enzymatic preparations, adsorbed lipase showed highest specific activity in pentane (14.2 U/mg) which is over 230 times higher than that of the soluble Aspergillus sp. lipase preparation (0.06 U/mg). Moreover, this enzymatic preparation proved to be an effective catalyst for natural flavour compound 2-phenylethylbutanoate synthesis. Reaction conversion of over 90 % was achieved under optimised conditions. Reusability of adsorbed Aspergillus sp. lipase preparation for the 2-phenylethylbutanoate enzymatic synthesis was investigated, resulting in a steady decrease of 20-30 % in enzymatic efficiency by each cycle. |
