Novel approach for downstream processing of phytosterol bioconversion

Abstract BACKGROUND Downstream processing is an important part of industrial steroid biotechnology. The traditional recovery methods require significant amounts of the organic solvents which are associated with environmental risks. There is a need for environmentally friendly downstream processing which also may open the prospects for regeneration and repeated use of the costly materials. RESULTS Microbial conversion of phytosterol to C17‐ketosteroids in methylated cyclodextrin (mCD) solutions was studied as a model bioprocess. Quantitative aspects of competitive complexation of mCD and natural β‐CD (β‐CD) with steroids were studied under different temperature modes and CD concentrations. The method of steroid recovery based on precipitation of insoluble β‐CD complexes ensured the complete isolation of androst‐4‐ene‐3,17‐dione, androsta‐1,4‐diene‐3,17‐dione, 9α‐hydroxyandrost‐4‐ene‐3,17‐dione, 20‐hydroxymethyl‐pregna‐1,4‐dien‐3‐one and 3β‐hydroxyandrost‐5‐en‐17‐one from aqueous media. Analysis of the 1H nuclear magnetic resonance (NMR) spectra showed a constant molar ratio of β‐CD to steroid equal to 2 in the obtained steroid β‐CD complexes. The extraction of the steroid from the β‐CD complex by small volumes of organic solvent provided a quantitative yield. The method developed ensures regeneration and repeated use of the mCDs without decrease of the basic bioconversion outputs, as was demonstrated in a series of phytosterol to androsta‐1,4‐diene‐3,17‐dione bioconversions by Mycolicibacterium neoaurum VKM Ac‐1816D. CONCLUSIONS Downstream processing based on manipulation of steroid solubility in aqueous cyclodextrin solutions is a promising alternative to traditional steroid extraction with organic solvents. This environmentally friendly approach ensures re‐use of materials without decrease in bioconversion outputs. © 2023 Society of Chemical Industry (SCI).