Advances in the 16α-hydroxy transformation of hydrocortisone by Streptomyces roseochromogenes

• First-time studied pH and T effects on S. roseochromogenes 16α-hydroxylation of hydrocortisone.
• Conversion at 26 °C and pH 6 led to a 95% 16α-hydroxyhydrocortisone on total product ratio.
• Two-step substrate addition resulted suitable for 1.0 g/L hydrocortisone transformation.
• Fed-batch fermentation improved transformation up to 0.807 g/L of 16α-hydroxyhydrocortisone.
• Proposed reverse phase purification drove to 85% recovery of 16α-hydroxyhydrocortisone.

The biotechnological transformation process of hydrocortisone to 16α-hydroxy hydrocortisone, a precursor of the widely used anti-inflammatory drug desfluorotriamcinolone, performed by Streptomyces roseochromogenes, requires high conversion ratios, low by-product formation, and a good product recovery after microbial conversion. To reach these targets, in this research, new whole cell transformation and chromatographic purification approaches were exploited. The optimal pH and temperature settings for the microbial conversion were first studied in shake flasks and then in 2.5-L batch experiments. Pulsed feedings during fermentations, coupled with a two step substrate addition approach, pushed to a transformation ratio of 63.0 ± 3.0%, starting from 1 g L−1 of substrate. By employing a DO-stat feeding strategy in 22-L fed-batches the transformation ratio increased up to 80.0 ± 2.0% with a ratio of 16α-hydroxy hydrocortisone on the total products of 94.5 ± 0.4%. In addition a new protocol for the 16α-hydroxy hydrocortisone purification, directly from the broth supernatant, was set up by using reverse phase chromatography reaching a 85.0 ± 2% product recovery with a product purity grade of 93.0 ± 2.0%.

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