Entrapment of mycelial fragments in calcium alginate: A general technique for the use of immobilized filamentous fungi in biocatalysis

Transformation reactions on 3β,17β-dihydroxyandrost-5-ene using free fungal cells were compared with those carried out by macerated mycelia, immobilized in calcium alginate beads. Six fungi were utilized in this study, namely Rhizopus oryzae ATCC 11145, Mucor plumbeus ATCC 4740, Cunninghamellaechinulata var. elegans ATCC 8688a, Aspergillus niger ATCC 9142, Phanerochaetechrysosporium ATCC 24725 and Whetzeliniasclerotiorum ATCC 18687. The results show, for the first time, that encapsulated mycelial fragments essentially carry out the same bioconversions as those observed with growing cells. As the immobilized cells were “resting”, the products formed were free of contamination by natural products, and this greatly aided the purification of the metabolites. Conditions for bead preparation were optimized. Furthermore, it was noted that the beads could be reused, once they had been subjected to a rejuvenation process.

Mycelial fragments from six filamentous fungi were used to biotransform 3β,17β-dihydroxyandrost-5-ene. Substrate was functionalised at sites as indicated.Figure optionsDownload as PowerPoint slideHighlights
► Encapsulation of macerated fungal hyphae with calcium alginate.
► Use of immobilized filamentous fungi to carry out biotransformations.
► First report where encapsulated fungi have hydroxylated a steroid.
► Investigation in which immobilized fungal cells were rejuvenated.