Biosynthesis Of Citronellyl Esters Using Lipase From Rhizopus Chinensis In Non-aqueous Phase

Abstracts: Fatty acid esters of the terpene alcohol, citronellol, are important flavor and fragrance compounds used in the food, beverage, cosmetic and pharmaceutical industries. Compared with the traditional chemical method, utilization of enzymes is of great value both in academy and practical application, because of the mild reaction condition, high conversion, less side reactions and environment pollution of enzyme-catalyzed reaction. Mycelium-bound lipase from Rhizopus chinensis (RCL) was adopted to catalyze the synthesis of citronellyl esters. Differen reaction systems was used according to the chain of fatty acid. And the extraction of product was also carried out.At first, compared with 10 commercial lipases, mycelium-bound lipase from Rhizopus chinensis (RCL) was proved to be most suitable for the synthesis of citronellyl hexanoate economically in solvent free system. Several reaction parameters in the lipase catalyzes esterification were investigated, the conversion of 98.8% was obtained by alcohol/acid molar radio of 1.25, 40 U/ml lipase addition, rotation speeds 150 r/min and temperature 40℃. In order to initialize the substrate efficiently and product refining, other approaches were further performed to improve the conversion of the product using equal molar substrate. Changing reaction equilibrium might be a telling way to increase the conversion. In closed system while equimolar substrate couldn't achieve relatively higher conversion. It was revealed that water content was the key factor affecting the conversion using equimolar substrates in closed system. To improve the production of the citronellyl hexanoate, a skillful approach with an external dewatering system was established to remove the by-product water. The new method kept the water content in a low level, and the conversion of the product ester was reaching to nearly 100% in 24 h with equimolar substrates.Because of the strongly inhibition to RCL of the short-chain acid, organic solvents was usedin the synthesis of citronellyl acetate. In this dissertation, the optimum preparation of RCL and catalytic reaction of resolution of citronellyl acetate was determined. It is as follows: memorial pH value 6~7, organic media heptane, rotation speeds 200 r/min, temperature 40℃. To further investigate the prospect of RCL to employ in industry, substrate concentration was optimized and stability of every reaction batchs was also studied. The result indicated RCL kept stable and citronellol conversion kept high even after 8 batchs. Meanwhile,because of the difference of boiling points from two products, the vacuum distillation which was utilized to separate the heptane and citronellyl acetate showed good result.In the reaction system, RCL showed a splendid prospect for industrial synthesis of citronellyl esters. It could be valuable toward the industrial scale-up.