Production of drug metabolites by immobilised Cunninghamella elegans: from screening to scale-up

Cunninghamella elegans is a fungus that has been used extensively as a microbial model of mammalian drug metabolism, whilst its potential as a biocatalyst for the preparative production of human drug metabolites has been often proposed, little effort has been made to enable this. Here, we describe a workflow for the application of C. elegans for the production of drug metabolites, starting from well-plate screening assays leading to the preparative production of drug metabolites using fungus immobilised either in alginate or as a biofilm. Using 12- and 96-well plates, the simultaneous screening of several drug biotransformations was achieved. To scale up the biotransformation, both modes of immobilisation enabled semi-continuous production of hydroxylated drug metabolites through repeated addition of drug and rejuvenation of the fungus. It was possible to improve the productivity in the biofilm culture for the production of 4′-hydroxydiclofenac from 1 mg/l h to over 4 mg/l h by reducing the incubation time for biotransformation and the number of rejuvenation steps.