Introduction

For over half a century microbial transformation has remained an area of increasing interest due to the facile conversion of substrates to oxygenated analogues, and its economic advantages over the use of isolated enzymes. These reactions are facilitated by cytochrome P450 enzymes, which can transform a typical carbon-hydrogen bond on a substrate into a carbon bearing a hydroxyl group.1,2As a result, fungi and other microorganisms are able to perform functionalization on substrate carbons that are thought to be chemically isolated.3 This investigation explores the use of filamentous fungi to effect the biotransformation of 17β -hydroxyandrost-4-en-3-one (1).

This project features the technique of cell immobilization, which involves trapping mycelial fragments in a calcium alginate polymer. Furthermore, employment of this method allows for the combinationinvolving several microorganisms in a single fermentation vessel.

Methodology

Figure 1: Free cell fermentation process

1. The fungal cultures are maintained on potato dextrose agar (PDA) slants.
2. The substrate (1) is fed to a 3 day old liquid culture of thegrowing fungus.
3. The contents are filtered and extracted with ethyl acetate.

Figure 2: Immobilized cell fermentation process.

1. The 3 day old growing fungal cells areharvested for calcium alginate entrapment.
2. The suspension of macerated mycelium in sodiumalginate solution is dripped slowly into a calcium chloride solution.
3. The substrate is fed to flasks containing the immobilized cells

Results

Products of biotransformation obtained from filamentous fungi.Rhizopus stolonifer yielded compounds 2,3,4,5and 6. Mucor plumbeus gave compounds 4,7 and8, whereas fermentation with Calonectria decora yielded compounds 4 and 9.

Conclusion

Several substrate analogues were created in a week by incubating testosterone with various filamentous fungi.

Relevance and Potential Application

Quick and easy synthesis of potentially bioactive steroids as pharmaceutical drugs.