One of the major advantages of using biocatalysts in organic synthesis is that water constitutes the reaction medium. However, water becomes a serious problem when bioconversion deals with lipophilic compounds, in particular those poorly soluble in water such as sterols. Bioconversion of lipophilic compounds depends on the close contact between the hydrophobic substrate and the biocatalyst. Increasing this contact requires usually the use of huge amounts of chemical which are often toxic, flammable and explosive. In this work, we showed that passive cell immobilization in porous materials can increase the contact between microorganisms and lipophilic substrates without using chemicals. The side chain cleavage of sterols was studied as a model multistep microbial bioconversion of lipophilic compounds. This reaction allows the production of androstenones which are the natural precursors of steroids. Among the studied immobilization carriers, the dried fruit of Luffa cylindrica was the most efficient Compared to other organic support carrier such as alginate beads, polyurethane foams, silicones and plastics, the dried fruit of Luffa cylindrica is advantageous since it is natural, renewable, biodegradable, cheap, mechanically strong, free of toxicity and it doesn't need a chemical pretreatment.
