Steroid transformation in a laboratory-scale glass air-lift fermenter.

A glass airlift fermenter, 1550 ml working volume, was used for microbiological transformation of phytosterols. A gas hold-up of 1.6% was observed with the lowest superficial gas velocity (1.89 cm/s). The volumetric liquid circulation rate remained relatively constant (0.21 l/s to 0.23 l/s) for superficial gas velocity values up to 11.37 cm/s. A 72% conversion of sitosterol to 1,4-androstadiene-3,17-dione was obtained.