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

Transformation reactions on 3ß,17ß-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, Cunninghamella echinulata var. elegans ATCC 8688a, Aspergillus niger ATCC 9142, Phanerochaete chrysosporium ATCC 24725 and Whetzelinia sclerotiorum 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.

Hydroxylation of steroids by Fusarium oxysporum, Exophiala jeanselmei and Ceratocystis paradoxa.

The potential of Fusarium oxysporum var. cubense UAMH 9013 to perform steroid biotransformations was reinvestigated using single phase and pulse feed conditions. The following natural steroids served as substrates: dehydroepiandrosterone (1), pregnenolone (2), testosterone (3), progesterone (4), cortisone (5), prednisone (6), estrone (7) and sarsasapogenin (8). The results showed the possible presence of C-7 and C-15 hydroxylase enzymes. This hypothesis was explored using three synthetic androstanes: androstane-3,17-dione (9), androsta-4,6-diene-3,17-dione (10) and 3α,5α-cycloandrost-6-en-17-one (11). These fermentations of non-natural steroids showed that C-7 hydroxylation was as a result of that position being allylic. The evidence also pointed towards the presence of a C-15 hydroxylase enzyme. The eleven steroids were also fed to Exophialajeanselmei var. lecanii-corni UAMH 8783. The results showed that the fungus appears to have very active 5α and 14α-hydroxylase enzymes, and is also capable of carrying out allylic oxidations. Ceratocystis paradoxa UAMH 8784 was grown in the presence of the above-mentioned steroids. The results showed that monooxygenases which effect allylic hydroxylation and Baeyer-Villiger rearrangement were active. However, redox reactions predominated.