Abstract
BackgroundPinoresinol is a high-value plant-derived lignan with multiple health supporting effects. Enantiomerically pure pinoresinol can be isolated from natural sources, but with low efficiency. Most chemical and biocatalytic approaches that have been described for the synthesis of pinoresinol furnish the racemic mixture. In this study we devised a three-step biocatalytic cascade for the production of enantiomerically pure pinoresinol from the cheap compound eugenol. Two consecutive oxidations of eugenol through vanillyl-alcohol oxidase and laccase are followed by kinetic resolution of racemic pinoresinol by enantiospecific pinoresinol reductases.ResultsThe addition of the enantiospecific pinoresinol reductase from Arabidopsis thaliana for kinetic resolution of (±)-pinoresinol to an in vitro cascade involving the vanillyl-alcohol oxidase from Penicillium simplicissimum and the bacterial laccase CgL1 from Corynebacterium glutamicum resulted in increasing ee values for (+)-pinoresinol; however, an ee value of 34 % was achieved in the best case. The ee value could be increased up to ≥99 % by applying Escherichia coli-based whole-cell biocatalysts. The optimized process operated in a one-pot “two-cell” sequential mode and yielded 876 µM (+)-pinoresinol with an ee value of 98 %. Switching the reductase to the enantiospecific pinoresinol lariciresinol reductase from Forsythia intermedia enabled the production of 610 µM (−)-pinoresinol with an ee value of 97 %.ConclusionA new approach for the synthesis of enantiomerically pure (+)- and (−)-pinoresinol is described that combines three biotransformation steps in one pot. By switching the reductase in the last step, the whole-cell biocatalysts can be directed to produce either (+)- or (−)-pinoresinol. The products of the reductases’ activity, (−)-lariciresinol and (−)-secoisolariciresinol, are valuable precursors that can also be applied for the synthesis of further lignans.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0472-0) contains supplementary material, which is available to authorized users.
Highlights
Pinoresinol is a high-value plant-derived lignan with multiple health supporting effects
In the present study we describe the implementation of this cascade into whole-cell biocatalysts and the addition of a third enzymatic step allowing the synthesis of enantiopure (+)-pinoresinol 3a or (−)-pinoresinol 3b
In this work we investigated the potential of kinetic resolution for the enrichment of enantiopure (+)-pinoresinol 3a by AtPrR2 and (−)-pinoresinol 3b by FiPLR
Summary
Pinoresinol is a high-value plant-derived lignan with multiple health supporting effects. Pure pinoresinol can be isolated from natural sources, but with low efficiency. Most chemical and biocatalytic approaches that have been described for the synthesis of pinoresinol furnish the racemic mixture. In this study we devised a three-step biocatalytic cascade for the production of enantiomerically pure pinoresinol from the cheap compound eugenol. Pinoresinol 3 is mainly isolated from seeds, fruits, and vegetables with low efficiency, but sometimes with high enantiopurity [12,13,14]. Ricklefs et al Microb Cell Fact (2016) 15:78 been described These synthetic approaches start from simple and abundant low-value compounds (for example methyl acetoacetate), but require multiple steps and intensive work-up [15]. The absence of an inexpensive production process and the large number of potential applications make pinoresinol 3 a highvalue compound with growing interest from an economic point of view
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