Enzymatic Synthesis Of Menthyl Acetate In Nonaqueous Medium

Non-aqueous enzymology, as an emerging field of enzyme catalysis, has developed less than 20 years.However, with the deepen and systemetic studies of the structural characteristics, catalytic mechanism and catalytic condition of enzyme in non-aqueous media, studies on non-aqueous enzymology and its development are becoming increasingly broad. The paper studies lipase-catalyzed synthesis menthyl acetate in non-aqueous medium. The main contents are as follows:In the first part, taking lipase [Candida rugosa lipase (CRL)] as a catalyst, n-hexane as solvent, the researcher synthesizes menthyl acetate by the esterification. The best reaction conditions are as follows: lipase amount is 2mg, the molar ratio of menthol to acetic acid is 1:1, substrate concentration of acetic acid and menthyl alcohol are all 0.1mol/L, temperature is 40℃, reaction time is 48 hours. Under these conditions, the esterification conversion of reaches to 92.4%.In the second part, taking the lipase[Candida rugosa lipase(CRL)] as a catalyst, the researcher catalytic synthesizes menthyl acetate in reverse micelles system of AOT/n-hexane. The best reaction conditions of the system are as follows: substrate concentration is 0.2mol/L (acetic acid), the molar ratio of menthol to acetic acid is 1:2, the amount of enzyme is 3mg, the amount of reverse micelle solution is 10mL, concentration of AOT is 0.05mol/L, the reaction temperature is 40℃, pH of buffer solution is 7.0, water content is W0=10, the reaction time is 48 hours. Under these conditions, the reaction conversion rate reaches to 85.3%, which is not so high.In the third part, taking the lipase [Candida rugosa lipase (CRL)] as a catalyst, the researcher catalytic synthesizes menthyl acetate in reverse micelles system of CTAB/n-hexane. The best reaction conditions of the system are as follows: substrate concentration is 0.4mol/L (acetic acid), the molar ratio of menthol to acetic acid is 1:4, the amount of enzyme is 4mg, reverse micelle solution is 10mL, concentration of CTAB is 0.05mol/L, reaction temperature is 38℃, pH of buffer solution is 7.5, water content is W0=9, reaction time is 48 hours. The reaction conversion rate reaches to 81.3% , which is not high.In the fourth part, the researcher first does biological imprint on the lipase [Candida rugosa lipase(CRL)] , and then studies the reaction of imprinted lipase [Candida rugosa lipase(CRL)] catalytic synthesize menthyl acetate, as well as the activity and stability of imprinted lipase. The results show that the increase of the activity of the imprinted enzyme depends on the reaction media, amount of water, the imprinted model and so on. Taking the n-hexane as the reaction medium, the researcher finds that while the reaction temperature is 40℃, the amount of water is 100μL and the imprinted model is C8-acid.