Resolution Of Racemic Ethyl 6-hydroxy-8-chlorocaprylate By Microorganism

Biocatalysis and chiral synthesis is gaining increasing attention nowadays due to its advantages such as mild reaction condition, high selectivity and environmental benign. In this thesis, the hydrolytic resolution of racemic ethyl 6-hydroxy-8-chlorocaprylate to optically active (R)-ethyl 6-hydroxy-8-chlorocaprylate catalyzed by microorganisms in aqueous phase was studied.A strain T4 producing lipase which catalyzed the resolution of racemic ethyl 6-hydroxy-8-chlorocaprylate to optically active (R)-ethyl 6-hydroxy-8-chlorocaprylate was screened from oily soil samples. The strain was identified as rod bacteria.The optimum fermentation conditions for the lipase production and cell growth are as follow: 40 g/L bean cake as carbon source, 20 g/L glycerin ,5 g/L peptone, 5 g/L carbamide as nitrogen, 5 g/L KH2PO4, 1 g/L MgSO4·7H2O, temperature 37°C, initial pH 8.0, and fermentation time 24 h.The optimum resolution conditions of racemic ethyl 6-hydroxy-8-chlorocaprylate are as follow: temperature 30 oC, buffer system pH 7.0, and shaking rate 170 r/min. Under the optimal condition as above, a substrate enantionmeric excess (e.e.) of 92.8% was achieved with a yield of 27.3% after 8 h of reaction. After ethyl acetate extraction at pH 10 followed by vacuum distillation, the product purity reached 89.4% with a yield of 31.5%.It was shown that the aqueous-organic biphasic system was superior to the aqueous system for the whole cell-catalyzed reaction. Reaction parameters, such as various solvents, water contents, conversion times, as well as enantioselectivity were studied. Octanen was found to be the most efficient solvent. Substrate conversion rate and enantionmeric excess (e.e.) reached to 76.3% , 91.3% in the aqueous-octanen reaction system .