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Biotransformations, which are often used for the production of important chemicals, can be carried out in aqueous or non-conventional media (which includes organic solvents, ionic liquids, supercritical fluids, gas-solid reaction etc.). Organic compounds like esters, aldehydes, alcohols etc. are produced by these methods. Esters are used in a variety of industries such as perfumery, flavor, pharmaceuticals, plasticizer, solvents and intermediates. They represent one of the most important natural fragrances, and are often produced by traditional methods like extraction from plant material or chemical synthesis. These processes employ polluting liquids as catalysts or solvents and are not considered environmentally friendly. The alternative of using lipases as catalysts for ester synthesis is very promising; however there are certain difficulties with these processes as well. Organic acid as one of the substrates in the esterification reaction catalyzed by lipases can decrease the enzyme activity. That is why it is interesting to carry out these processes in the non-conventional environments. Many scientists have studied the lipase catalyzed esterification processes in ionic liquids as a solvent. It is now known that they might improve enzyme stability in comparison to the solvent free system. This was one of the topics of our prior Hungarian-Croatian bilateral cooperation on the subject of two esterifications: the synthesis of ethyl lactate and isoamyl acetate. The first objective of this project is to pursue the work on lipase catalyzed esterifications, to conduct them in other non-conventional media - solid-gas phase environment; as well as to continue the work in ionic liquids and organic phase, and to emphasize the differences of these processes in different media from an engineering point of view. The work on the gas-phase biotransformation has been started years ago and it is now well established that lipases can be used in such media. For those systems where substrates can be vaporized, gas-phase catalysis offers certain advantages: diffusivities in the gas phase are orders of magnitude higher than in water and by that mass transfer limitations are eliminated, most organic substrates are poorly soluble in water, simplified product separation, recovery of the biocatalyst is simplified because the biocatalyst is in solid state. On the other hand, ionic liquids as green solvents represent an interesting media to work with due to its good physical properties, reusability and the ability to positively influence the enzyme, stability, activity and enantioselectivity. Alcohols as other industrially important compounds mentioned in this project are used for the production of optically active compounds in the pharmaceutical industry. They can be produced by the action of an enzyme alcohol dehydrogenase found in cheap baker's yeast. It is known that baker's yeast can be used in the non-conventional environment (organic solvent, solid-gas biocatalysis), so the other objective of this work is to use baker's yeast as a catalyst in the reaction of oxidoreduction. It is necessary to consider coenzyme regeneration in these reaction systems to improve the substrate conversion, i.e. to shift the conversion towards the wanted products.
Short description of the task performed by Croatian partner
One of the topics of this projects were lipase catalyzed esterifications. Esterification of lactic acid and ethanol is industrially very interesting, but quite unstudied reaction.The reaction was catalyzed by Candida antarctica B (Novozyme 435) in ionic liquid (Cyphos 104). The influence of different variables on lipase enantioselectivity and lactic acid conversion was investigated. The variables investigated were ionic liquid mass/lipase mass ratio, water content, alcohol excess and temperature. Using the Design Expert software 23 factorial experimental plan (two levels, three factors) was performed to ascertain the effect of selected variables and their interactions on the ethyl lactate enantiomeric excess and lactic acid conversion. A paper was published on the basis of these results. Other esterification reactions were studied as well. The results of the joined work were presented at different conferecnces. During the project students from the University of Zagreb have worked at the Institute in Veszprem on different project related topic s (isoamyl acetate synthesis, esterification of fusel oil and ethanol etc.). They have presented the results of their work on several conferences.
Ovo web sjedište koristi tehnologiju "kolačića" (eng. cookie) da bi se korisnicima prikazao dinamičan i personaliziran sadržaj, te su oni nužni za ispravan rad. Ako nastavite pregledavati ove stranice, kolačići će biti korišteni u suradnji s vašim preglednikom Weba.
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