Abstract
Aromatic substances are widely applied in the creation of fragrances for cosmetic, detergent and food products, as well as medical preparations for external use. Environmentally friendly enzymes obtained using green chemistry methods are of particular value. Therefore, the enzymatic synthesis of esters of aromatic aliphatic acids and aromatic alcohols is of great practical interest. This approach has significant advantages over chemical methods, since it is carried out at low temperatures without the formation of byproducts, thus requiring no special purification techniques. Although the cost of enzyme preparations is rather high, immobilized enzymes can be used repeatedly and continuously. In the present work, we investigate the possibility of using non-immobilized freeze-dried lipase (Lipase from porcine pancreas, Type 11) for repeated esterification of butyl alcohol with butyric acid. The synthesis was carried out in hexane. The completeness of the process was controlled by titration of the residual acid with aqueous alcoholic alkali in the reaction medium. The resulting enzyme preparation was separated from the reaction mixture and reused with a new portion of the substrate. It is shown that the obtained enzyme can be used for more than 10 cycles. It was found that, starting from the second cycle, the enzyme activity increases depending on its concentration in the medium. In addition, the butyric acid conversion increases by 6–180% reaching the initial level only after the 10th cycle. The unusual effect of increasing the enzymatic activity of lipase in recycles can be explained by both the phenomenon of autocatalysis, i.e. activation of the enzyme by water released as a result of esterification, and structural features of the active site of pancreatic lipase.
Highlights
Aromatic substances are widely applied in the creation of fragrances for cosmetic, detergent and food products, as well as medical preparations for external use
We investigate the possibility of using non-immobilized freeze-dried lipase (Lipase from porcine pancreas, Type 11) for repeated esterification of butyl alcohol with butyric acid
The completeness of the process was controlled by titration of the residual acid with aqueous alcoholic alkali in the reaction medium
Summary
2. Ферментативный синтез бутилбутирата панкреатической липазой: концентрация препарата − 2,6 мг/мл; температура процесса – 35 °С; скорость перемешивания − 70 об./мин. 3. Ферментативный синтез бутилбутирата панкреатической липазой: концентрация препарата 20 мг/мл; температура процесса – 35 °С; без перемешивания. Косвенным подтверждением этого может служить тот факт, что при сравнении этерифицирующей способности некоторых липаз (панкреатическая липаза, Lipozyme CALB и Lipozyme TL IM) при синтезе бутилбутирата в равных условиях для ферментов (концентрация кислоты 0,1 N, мольное соотношение кислота:спирт = 1:2) нами обнаружено, что панкреатическая липаза, в отличие от других ферментов, показывает индукционный период около одного часа, когда процесс практически не идет Нужно учесть особенность упаковки активного центра липазы, которая также может повысить активацию липазы за счет постепенного более полного раскрытия «крышки» и тем самым повысить доступность активного центра липазы
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