Abstract:
The main objective of this study is to synthesize biofragrance "amyl acetate" naturally extractable from the flowers of the Thai plant called "Nom Maew" (Rauwenhoffia siamenesis Scheff.) by a biotechnological method. Lipases from various microorganisms namely Aspergillus niger, Candida cylindracea, Pseudomonas species and Mucor miehei were applied to catalyze the synthetic reaction between amyl alcohol and octyl acetate through the process of "transesterification". The reaction mixture was incubated in organic solvent, hexane, at 40 ํC, with continous stirring by magnetic stirrer. The products were then sampled after 72 hours and analyzed by HPLC. From the results, the percent conversion of 41, 16.37 and 9.43 were obtained from the lipases of Aspergillus niger, Pseudomonas spp and Mucor miehei respectively. The product obtained from the reaction catalysed by lipases from Candida cylindracea was unmeasurably low. When the immobilized enzymes were comparatively studied between Aspergillus niger and Mucor miehei, the results obtained showed highest conversion, i.e. 64.53% from the catalysis by lipases from Aspergillus niger, compared to 56.73% obtained from Mucor miehei. Furthermore, the results from kinetic studies also exhibited rapid conversion to maximal yield obtained from immobilized lipases from Aspergillus niger. It could be seen that both free and immobilized forms of lipases from Aspergillus niger resulted in better conversion than lipases from other studied microorganisms. The transesterification reactions between amyl alcohol and substrates with various numbers of carbon chain length were studied. The reactions were catalysed by immobilized lipase from Aspergillus niger in the presence of n-hexane.Amyl acetate obtained from the transesterification was analyzed by HPLC and the kinetics of the reaction were studied. The V[subscript max]/K[subscript m] from the reactions containing ethyl, propyl, butyl, hexel and octyl as substrated were obtainedas follows, 41.44, 32.97, 29.50, 20.22 and 6.70 [micro]mol/mM/min/gram of enzyme respectively. From this result, it could be postulated that immobilized lipase from Aspergillus niger appeared to be more specific to ethyl acetate than the other studied substrates in producing the required amyl acetate in the presence of n-hexane.
