Applied Microbiology and Biotechnology, Vol.97, No.17, 7659-7667, 2013
Enzymatic production of Cilastatin intermediate via highly enantioselective hydrolysis of methyl (+/-)-2,2-dimethylcyclopropane carboxylate using newly isolated Rhodococcus sp ECU1013
(S)-(+)-2,2-Dimethylcyclopropane carboxylic acid [(S)-(+)-DMCPA] is a key chiral intermediate for production of Cilastatin, an excellent renal dehydropeptidase-I inhibitor. In this study, a new method for preparation of (S)-(+)-DMCPA with microbial esterases was investigated. A microbial screening program obtained six esterase-producing isolates that could display relatively high activities and enantioselectivities using racemic ethyl 2,2-dimethylcyclopropane carboxylate (DMCPE) as screening substrate, aiming at forming optically pure (S)-(+)-DMCPA. Further selection was carried out with substrates having different alcohol moieties, including methyl, ethyl, and 2-chloroethyl esters. Finally, one of these strains, numbered ECU1013, with high enantioselectivity toward the hydrolytic resolution of methyl 2,2-dimethylcyclopropane carboxylate (DMCPM), afforded the (S)-product in 92 % ee, and was later identified as Rhodococcus sp. According to our research, there were several active esterases to DMCPM in cells of Rhodococcus sp. ECU1013; however, (S)-preferential esterase was selectively enriched based on the time-dependent profile of esterases biosynthesis, thereby the enantiomeric excess of biotransformation product (ee (p)) was constantly increased, finally maintained at 95 % (S). To improve the yield, various organic solvents were employed for better dispersion of the hydrophobic substrate. As a result, (+/-)-DMCPM of up to 400 mM in the organic phase of isooctane was enantioselectively hydrolyzed into (S)-(+)-DMCPA, with an isolation yield of 38 % and a further increase of ee (p) to 99 %.
Keywords:Microbial esterase;Rhodococcus sp;Enantioselective hydrolysis;Methyl 2,2-dimethylcyclopropane carboxylate;(S)-(+)-2,2-Dimethylcyclopropane carboxylic acid;Biphasic system