A competitive approach for the reduction of unsaturated compounds based on fungal ene-reductases

The aim of this work was to select potential biocatalysts for the reduction of unsaturated compounds. The ability of Gliomastix masseei, Mucor circinelloides, Mucor plumbeus, Penicillium citrinum and Syncephalastrum racemosum to convert structurally diverse substrates was tested, also considering the role of substituents linked to the C=C bond on the process efficiency. All the tested fungi expressed ene-reductase activity when tested with several types of compounds; the ketone derivative was the best substrate, followed by the nitroalkene and the unsaturated aldehyde, whereas the ester was the most recalcitrant to bioreduction. The results highlighted the potential of Mucor circinelloides MUT 44 and Mucor plumbeus MUT 2769 as versatile whole-cell systems; fast and efficient reduction was obtained using these biocatalysts for most of the compounds. Comparative analysis of the substrate spectrum was performed for three Mucor circinelloides strains, and reaction rates and timings were shown to vary, indicating a strong physiological diversity of ene-reductase activity at the intraspecific level.