Production by Clonostachys compactiuscula of a lovastatin esterase that converts lovastatin to monacolin J

Abstract

The conversion of monacolin K (lovastatin) to monacolin J, a core structure in the synthesis of other statins, was achieved using the fungus Clonostachys compactiuscula and optimized with response surface methodology. To study the proposed second-order polynomial model, a central composite experimental design with multiple linear regression was used to estimate the model coefficients of five selected factors believed to influence the conversion process. The experimental results indicated that the optimal conditions for growth of C. compactiuscula mycelium were as follows: 2.0 g glucose/L, initial pH of the medium 8.5, and incubation of the mycelium for 4 days. These conditions yielded an optimal concentration of the substrate lovastatin of 1 mg/mL, and a conversion time of 15 h. A lovastatin esterase was isolated and purified from the mycelium of C. compactiuscula by ammonium sulfate precipitation, size-exclusion chromatography, and ion-exchange chromatography. Following SDS-PAGE, the purified enzyme appeared as a single band with an apparent molecular mass of 28 kDa. The converted product, monacolin J, was isolated and purified, and its structure was analyzed by NMR. © 2006 Elsevier Inc. All rights reserved.