Enzymatic lactic acid esterification in ionic liquids and supercritical carbon dioxide

Transcription

1 UNIVERSITY OF PANNONIA DOCTORAL SCHOOL OF CHEMICAL ENGINEERING AND MATERIAL SCIENCES Enzymatic lactic acid esterification in ionic liquids and supercritical carbon dioxide Ph.D. THESES AUTHOR: Gergely Németh M.SC. ENVIRONMENTAL ENGINEER SUPERVISOR: Dr. László Gubicza PROFESSOR UNIVERSITY OF PANNONIA RESEARCH INSTITUTE ON BIOENGINEERING, MEMBRANE TECHNOLOGY AND ENERGETICS 2013

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3 PRELUDES, AIMS Recently there is a growing demand for development of technologies using renewable resources to replace the conventional industrial processes and solve the waste problem. Such widely used renewable chemicals are lactic acid and its esters which are mainly used in food industry as aromatic components, preservatives and emulsifiers as well as in pharmaceutical and cosmetics industry, furthermore lactic acid is the ingredient of biodegradable plastic. During my doctoral work the investigated reaction was the enzymatic enantioselective esterification of chemically synthetised racemic lactic acid applying two types of lipases (Candida antarctica lipase B, Candida rugosa), where the solvents were different organic solvents and environmentally friendly solvents. The latter were the supercritical carbon dioxide and different ionic liquids. Their solvent properties can be influenced by the reaction parameters and the chemical composition. The investigation of enzymatic enantioselective lactic acid esterification is an absolutely novel research area with a very few references in the literature. The aim of the work was to determine the optimal reaction circumstances where the ester yield and e.e. values are both high, and to ground the development of a new technology which produces the ingredient of biodegradable plastic. The temperature, the substrate ratio and the initial water content were examined in different conventional and non-conventional solvents.

4 EXPERIMENTAL METHODS Effects of the reaction parameters which have an effect on the activity of lipases were investigated in conventional solvents and ionic liquids in shaking incubator. Subsequently, the effects were followed in a high pressure reactor where the reaction was carried out in supercritical carbon dioxide and supercritical carbon dioxide/ionic liquid mixture. The water condensed during esterification was removed either by adding zeolite to the shaked reactor or by pervaporation device. The highest e.e. value, observed near the most favourable parameter values, was increased by the recirculation of (L) > (D)-lactic acid obtained from the synthetised product. THESES During my Ph.D. work the following novel scientific results have been achieved: 1. Lactic acid esterification was investigated in different medias regarding to the ester yield and enantioselectivity. There are no references in the literature to the investigation of enantioselective lactic acid esterification, accordingly this topic is a brand new research area. It was demonstrated when using n-hexane and alcohol excess as a solvent low enantioselectivity can be measured during enzymatic (Candida antarctica lipase B) ethyllactate synthesis. It was found that the highest yield in the media of n-hexane was 55% and the e.e. value was 20%, in alcohol excess the yield and the e.e. value were 81% and 22%, respectively, both cases after 24 hours. The catalytic activity was investigated of 10 Cyphos-type ionic liquids without any added enzyme during the esterification of lactic acid. Five of them had as low catalytic activity as to be a suitable solvent for my reactions. The ionic liquids with lowest catalytic activity at 30 C and the corresponding measured yields are the followings:

5 Cyphos 103: 9% Cyphos 104: 13% Cyphos 105: 6% Cyphos 109: 34% Cyphos 110: 26% Solvent free system: 2% Cyphos 104 was the most appropriate ionic liquid for being the media of enantioselective lactic acid esterification. After evaluating the datas of the experimental design it was proved that the highest ester yield (56%) and e.e. value (22%) (after 50% yield the e.e.=23%) could be observed at 30 C, near 11 alcohol/la ratio and 8 w/w% initial water content. (1. publication) 2. It was identified that the Candida antarctica lipase B showed higher activity than Candida rugosa near the same reaction conditions. The comparison of the two lipases was achieved near varying 4 reaction parameters (temperature, initial water content, alcohol/la ratio and IL/alcohol ratio). Based on the findings CALB showed higher ester yield as good as in case of all reaction conditions, and the enantioselectivity was higher in any case after 24 hours. (4. publication) 3. It was concluded that in scco 2 and scco 2 /IL mixture the ester yield could be higher than 100%, while the e.e. values were low. The results confirmed that the presence of Cyphos 104 ionic liquid in scco 2 has positive effect on the reaction near 35, 50 and 70 C and 100, 200, 300 bar pressure. Yields above 100% ( %) without addition of ionic liquid could be measured just at high temperature, on the contrary the e.e. values were higher (27-27%) at lower temperature near higher pressure after 1 hour reaction time. In case of adding ionic liquid at 30 C could be observed 120% ester yield, despite the enantioselectivity was not increased compared to the system without any ionic liquid. Comparing the scco 2 with the IL medium it was demonstrated that in Cyphos 104 ionic liquid as a solvent and using CALB enzyme the highest yield and e.e. values could be measured. (2. publication)

6 4. The maximal ester yield and e.e. values were observed applying CALB when the optimal values of temperature, alcohol/la ratio, initial water content and Cyphos 104 IL/alcohol ratios were determined. It was concluded that the optimal values could be find in the following intervals: C, 3-19 alcohol/la ratio, 2,5-16 w/w% initial water content, 0-2 IL/alcohol ratio. The best results were found at 30 C, near 1 alcohol/la ratio, 4 w/w% initial water content and 1 IL/alcohol ratio (y=77%, e.e. 1h =38%, e.e.(y=50%)=30%). (4. publication) 5. It was demonstrated that removal of the originate water during the raction was decreased the ester yield and the enantioselectivity, as well. The water was removed by adding zeolite (4Å) to the reaction mixture and by pervaporation (PERVAP 2201). Applying of zeolite compared to the reference mixture [y=92%, e.e.(y=50%)=30%] 86% and 80% yield and 24% és 25% e.e. values were observed (at y=50%) after 48 hours reaction time. In case of pervaporation after 5 hours the yield was 22% which is the same value like without pervaporation, and the e.e. value was 26% (reference mixture e.e.=34%). (3. publication) 6. It was concluded through theoretical calculations and experiments that the e.e. value, observed after a single reaction, could be increased when the substrate (lactic acid) obtained from the synthetized product is reacted again. The best result were obtained out the three methods (24 hours reactions, recycling after 50% or 30% yield) when recycling happened after 50% yield. The number of recycling and the costs are the lowest with this method (4x, e.e.=79%). (4. publication) 7. Decreasing of the enzyme activity was identified in Cyphos 104 ionic liquid. Based on the findings the ionic liquid has enzyme stabilizing effect. After 5 times recycling the yield was decreased from 77% to 20% in Cyphos 104, but without ionic liquid the initial yield (50%) was decreased to 9%. (4. publication)

7 LIST OF PUBLICATIONS ENGLISH PUBLICATIONS 1. Findrik, Z., Németh, G., Gubicza, L., Bélafi-Bakó, K., Vasić-Rački, Đ.: Evaluation of factors influencing the enantioselective enzymatic esterification of lactic acid in ionic liquid, Bioprocess and Biosystems Engineering 35 (2012) IF=1, Knez, Ž., Kavčič, S., Gubicza, L., Bélafi-Bakó, K., Németh, G., Primožič, M., Habulin, M.: Lipase-catalyzed esterification of lactic acid in supercritical carbon dioxide, Journal of Supercritical Fluids 66 (2012) IF=2, Findrik, Z., Németh, G., Vasić-Rački, Đ., Bélafi-Bakó, K., Csanádi, Zs., Gubicza, L.: Pervaporation-aided enzymatic esterifications in non-conventional media, Process Biochemistry 47 (2012) IF=2, Németh, G., Bélafi-Bakó, K., Nemestóthy, N., Gubicza, L.: Asymmetric lactic acid esterification with biocatalysts in ionic liquid, Hungarian Journal of Industrial Chemistry, 39 (2012) OTHER PUBLICATIONS Major, B., Németh, G., Bélafi-Bakó, K.,: Unique role of water content in enzymatic synthesis of ethyl lactate using ionic liquid as solvent, Chemical Papers 64 (2010) Németh, G.: Zöld oldószer, lebomló műanyag, Élet és Tudomány 40 (2011) Németh, G., Reich, K., Fazekas, B., Pitás, V., Kárpáti, Á., A rothasztott szennyvíziszap nehézfém-tartalmának csökkentési lehetősége, Hírcsatorna 3 (2009) Pitás, V., Németh, G., Reich, K., Fazekas, B., Biofilm hordozó hatása biofilmes/hibrid reaktorok működésére, Műszaki Információ. Környezetvédelem, 6 (2009) ORAL AND POSTER PRESENTATIONS IN ENGLISH Gubicza, L., Bélafi-Bakó, K., Csanádi, Zs., Németh, G.: Microwave assisted enzymatic esterification of lactic acid in phosphonium type ionic liquids, EUCHEM 2010, Conference on Molten Salts and Ionic Liquids, Bamberg, Germany, , pp. 149., poster Nemestóthy, N., Németh, G., Csanádi, Zs., Gubicza, L.: Continuous enzymatic esterification in pervaporation-aided system using ionic liquids as solvent, International Scientific Conference on Pervaporation, Vapor Permeation and Mambrane Distillation, Torun, Poland, , pp. 86., poster Németh, G., Nemestóthy, N., Findrik, Z., Gubicza, L.: Enantioselecive enzymatic esterification of lactic acid in ionic liquids, 37th International Conference of Slovak Society of Chemical Engineering, Tatranské Matliare, Slovakia, , pp , presentation

8 Németh, G., Csanádi, Zs., Findrik, Z., Gubicza, L.: Investigation of the enantioselectivity of different lipase enzymes during the esterification of lactic acid in ionic liquid cosolvent, Applied biocatalysis, 6 th meeting of students and university professors, Zágráb, Croatia, , pp. 9., presentation Németh, G., Csanádi, Zs., Bélafi-Bakó, K., Gubicza, L.: Effect of ionic liquids' properties on the enantioselective esterification of lactic acid, 8 th European Symposium on Biochemical Engineering Sciences, Bologna, Italy, , pp. 193., poster Németh, G., Kavčič, S., Nemestóthy, N., Habulin, M., Knez, Z., Gubicza, L.: Asymmetric esterification of low carbon atom number carboxylic acids in ionic liquid as a co-solvent, Slovenski kemijski dnevi 2010, , Maribor, Slovenia, pp. 132., presentation Németh, G., Bélafi-Bakó, K., Gubicza, L.: Enzymatic enantioselective esterification of lactic acid with low carbon chain alcohols in ionic liquids, 7 th International Conference on Renewable Resources and Biorefineries, , Bruges, Belgium, pp. 13., poster Németh, G., Habulin, M., Knez, Ž., Primožič, M., Gubicza, L.: Comparison of the enzymatic production of lactic acid ethyl ester in ionic liquid and supercritical CO 2, 2 nd Conference on Applied Biocatalysis and 7th Meeting of Students and University Professors from Maribor and Zagreb, Maribor, Slovenia, , pp. 49., presentation Németh, G., Findrik, Z., Vasić-Rački, D., Bélafi-Bakó, K., Gubicza, L.: Effect of ionic liquids on the enantioselectivity of Candida antarctica lipase B during lactic acid esterification, 9 th International Conference on Protein Stabilization, , Lisszabon, Portugal, pp. 43., poster ORAL PRESENTATIONS IN HUNGARIAN Gubicza, L., Németh, G., Csanádi, Zs., Bélafi-Bakó, K., Vrasalovic Presecki, A., Nemestóthy, N.: Enzimkatalitikus észterezés ionos folyadékokban, Veszprém, Műszaki Kémiai Napok, , pp Németh, G., Bányai, T., Nemestóthy, N., Findrik, Z., Gubicza, L.: Tejsav enantioszelektív észterezése Cyphos 104 ionos folyadékban, Műszaki Kémiai Napok, Veszprém, , pp Németh, G., Bányai, T., Nemestóthy, N., Findrik, Z., Gubicza, L.: Tejsav enantioszelektív észterezése Cyphos 104 ionos folyadékban, Műszaki Kémiai Napok, Veszprém, , pp Gubicza, L., Németh, G., Csanádi, Zs., Bélafiné Bakó, K., Vrasalovic Presecki, A., Nemestóthy, N.: Enzimkatalitikus észterezés ionos folyadékokban, Műszaki Kémiai Napok, Veszprém, , pp