László Gubicza

Enzymatic esterification in ionic liquids integrated with pervaporation for water removal

The application of ionic liquids as solvents for the enantioselective esterification of (R,S)-2-chloropropanoic acid with butan-1-ol using Candida rugosa lipase is reported. The role of water produced during the reaction and controlling of the water activity with pervaporation was studied. The enantioselective esterification of (R,S)-2-chloropropanoic acid with butan-1-ol in different organic solvents and ionic liquids was studied. The reaction was effectively catalysed by Candida rugosa lipase. From the ionic solvents investigated, the best results were achieved in [bmim]PF6. The presence of water had a strong effect on the activity of the lipase. Since in esterification reactions with acid and alcohol equimolar amounts of water are formed, the excess of water was removed and the water activity was kept constant using a pervaporation system without any additives. At the optimum water activity Candida rugosa lipase showed high thermal stability in [bmim]PF6 and it could be reused for at least five recycles with only a small lost of activity.

Application of pervaporation for removal of water produced during enzymatic esterification in ionic liquids

Abstract An enzymatic reaction in ionic liquids was studied with a special attention to the water content. Water, as a by-product of the esterification by lipase should be removed to enhance the synthesis. Pervaporation was studied for water removal in integrated system.

Membrane bioreactor for utilisation of carbohydrates in waste streams

Cellulose solution, as a model waste water was hydrolysed in a special, jacketed membrane bioreactor by Celluclast enzyme preparation to produce glucose. Stainless steel microfiltration tube membrane covered by a hairy pelt cloth was applied, which provided a surface for simultaneous adsorption of the substrate and the enzyme. Around 50% cellulose conversion was achieved in batch and continuous mode of operation.

Biocatalysts and membranes

Relationships between, and co-existence of, membranes and enzymes is ubiquitous throughout nature. Membranes provide essential barriers to the egress of intracellular biocatalysts, effectively retaining the enzymes while allowing transport of substrates and products to and from the surrounding environment. They also serve a screening function, allowing the passage of small molecules while preventing larger, potentially inhibitory molecules from coming into close contact with the enzyme/biocatalyst system. In addition to these two ‘filtration’ functions, membranes are often intimately involved in biocatalytic reactions, where one or more enzymes are bound to the membrane surface. In some cases the membrane is acting as biocatalyst support and orientation device, while in others the enzyme acts to facilitate the transport of molecules through the membrane.

Effect of Chain Length and Order of the Alcohol on Enzyme Activity During Enzymatic Esterification in Organic Media

Abstract Esters of short chain acids and alcohols are found in nature as compounds of flavors. Lately the method for their manufacture has been the enzymatic esterification in non-conventional media. Although several reactions have been studied in various media (organic solvents, ionic liquids, supercritical fluids, solvent-free systems), there has been no systematic investigation to clarify the effects of chain length and order of alcohols on the activity of the enzyme. In this work acetic acid was used as an acyl donor and the roles of the linear and branched chains of C2-C8 primary, secondary and tertiary alcohols on the activity of Novozym 435, the widely used lipase preparation were studied. Both the length of the carbon chain and the order of the alcohol were found to strongly influence the activity of the enzyme using the same operational parameters for the reactions. As a result of this project general conclusions were made with regard to the characters of alcohols affecting the reaction rates, which can be applied to other similar reactions.

APPLICATION OF IONIC LIQUIDS IN THE UTILIZATION OF THE AGRICULTURAL WASTES: TOWARDS THE ONE-STEP PRE-TREATMENT AND CELLULOSE HYDROLYSIS

Abstract Cheap, renewable lignocellulosic materials are relevant to the future of biofuel production. Wood and agricultural wastes (e.g. straw, corn stover) provide a raw material source that cannot be used for human consumption, thus biofuels from such sources do not threaten the food supply. The aim of the work was to carry out the pre-treatment and hydrolysis of lignocellulosic material in the same ionic liquid solvent (1-n-butyl-3- methyl-imidazolium-chloride, [Bmim]Cl), using ground wheat straw and a mixture of corn (Zea mays) leaf and stover, as substrates. Our measurements show that it is possible to achieve an acceptable glucose content from the cellulose by applying Cellic® CTec2 and Cellic® HTec2 enzyme complexes.