Enhancement of β-sitosterol Bioconversion by Fusarium solani Using Aqueous-organic Solvent System

The selective cleavage of the P--sitosterol side-chain by the free cells of Fusarium solani was studied to detect the combined effect of both solvent nature and concentration in two-phase aqueous organic medium. This multi-step degradation pathway of sterols leads to the production of 4-androstene-4, 17-dione (AD) and 1, 4- androstadiene 3, 17-dione (ADD). The bioconversion was strongly affected by the nature and by the aqueous/ organic phase ratio. Some androstenes are the key intermediates of microbial side-chain cleavage of phytosterol which is an alternative to the multistep chemical synthesis. An attempt was made in this study to improve the substrate-biocatalyst interaction in order to increase the bioconversion yield. Comparison study was held between n-hexane and toluene to study their effects on the bioconversion process in batch fermentation technique. The results showed that maximum AD and ADD yields (53.3,25% and 58.7,25.9%) was obtained by the addition of 10% n- hexane or toluene respectively to the production medium, at substrate concentration 30 mg/100ml medium, supplemented with 2 ml tween 80 and 0.2mg % glycine