Localization of 17beta-hydroxysteroid dehydrogenase in Mycobacterium sp. VKM Ac-1815D mutant strain

Bioproduction of testosterone from phytosterol by Mycolicibacterium neoaurum strains: "one-pot", two modes

The main male hormone, testosterone is obtained from cheap and readily available phytosterol using the strains of Mycolicibacterium neoaurum VKM Ac-1815D, or Ac-1816D. During the first "oxidative" stage, phytosterol (5-10 g/L) was aerobically converted by Ac-1815D, or Ac-1816D to form 17-ketoandrostanes: androstenedione, or androstadienedione, respectively. At the same bioreactor, the 17-ketoandrostanes were further transformed to testosterone due to the presence of 17β-hydroxysteroid dehydrogenase activity in the strains ("reductive" mode). The conditions favorable for "oxidative" and "reductive" stages have been revealed to increase the final testosterone yield. Glucose supplement and microaerophilic conditions during the "reductive" mode ensured increased testosterone production by mycolicibacteria cells. Both strains effectively produced testosterone from phytosterol, but highest ever reported testosterone yield was achieved using M. neoaurum VKM Ac-1815D: 4.59 g/l testosterone was reached from 10 g/l phytosterol thus corresponding to the molar yield of over 66%. The results contribute to the knowledge on phytosterol bioconversion by mycolicibacteria, and are of significance for one-pot testosterone bioproduction from phytosterol bypassing the intermediate isolation of the 17-ketoandrostanes.

Mycolicibacterium cell factory for the production of steroid-based drug intermediates

Steroid-based drugs have been developed as the second largest medical category in pharmaceutics. The well-established route of steroid industry includes two steps: the conversion of natural products with a steroid framework to steroid-based drug intermediates and the synthesis of varied steroid-based drugs from steroid-based drug intermediates. The biosynthesis of steroid-based drug intermediates from phytosterols by Mycolicibacterium cell factories bypasses the potential undersupply of diosgenin in the traditional steroid chemical industry. Moreover, the biosynthesis route shows advantages on multiple steroid-based drug intermediate products, more ecofriendly processes, and consecutive reactions carried out in one operation step and in one pot. Androsta-4-ene-3,17-dione (AD), androsta-1,4-diene-3,17-dione (ADD) and 9-hydroxyandrostra-4-ene-3,17-dione (9-OH-AD) are the representative steroid-based drug intermediates synthesized by mycolicibacteria. Other steroid metabolites of mycolicibacteria, like 4-androstene-17β-ol-3-one (TS), 22-hydroxy-23,24-bisnorchol-4-ene-3-one (4-HBC), 22-hydroxy-23,24-bisnorchol-1,4-diene-3-one (1,4-HBC), 9,22-dihydroxy-23,24-bisnorchol-4-ene-3-one (9-OH-HBC), 3aα-H-4α-(3'-propionic acid)-7aβ-methylhexahydro-1,5-indanedione (HIP) and 3aα-H-4α-(3'-propionic acid)-5α-hydroxy-7aβ-methylhexahydro-1-indanone-δ-lactone (HIL), also show values as steroid-based drug intermediates. To improve the bio-production efficiency of the steroid-based drug intermediates, mycolicibacterial strains and biotransformation processes have been continuously studied in the past decades. Many mycolicibacteria that accumulate steroid drug intermediates have been isolated, and subsequently optimized by conventional mutagenesis and genetic engineering. Especially, with the clarification of the mycolicibacterial steroid metabolic pathway and the developments on gene editing technologies, rational design is becoming an important measure for the construction and optimization of engineered mycolicibacteria strains that produce steroid-based drug intermediates. Hence, by reviewing researches in the past two decades, this article updates the overall process of steroid metabolism in mycolicibacteria and provides comprehensive schemes for the rational construction of mycolicibacterial strains that accumulate steroid-based drug intermediates. In addition, the special strategies for the bioconversion of highly hydrophobic steroid in aqueous media are discussed as well.

Identification and characterization of a 20β-HSDH from the anaerobic gut bacterium Butyricicoccus desmolans ATCC 43058

Members of the gastrointestinal microbiota are known to convert glucocorticoids to androstanes, which are subsequently converted to potent androgens by other members of the gut microbiota or host tissues. Butyricicoccus desmolans and Clostridium cadaveris have previously been reported for steroid-17,20-desmolase and 20β-hydroxysteroid dehydrogenase (HSDH) activities that are responsible for androstane formation from cortisol; however, the genes encoding these enzymes have yet to be reported. In this work, we identified and located a gene encoding 20β-HSDH in both B. desmolans and C. cadaveris The 20β-HSDH of B. desmolans was heterologously overexpressed and purified from Escherichia coli The enzyme was determined to be a homotetramer with subunit molecular mass of 33.8 ± 3.7 kDa. The r20β-HSDH displayed pH optimum in the reductive direction at pH 9.0 and in the oxidative direction at pH 7.0-7.5 with (20β-dihydro)cortisol and NAD(H) as substrates. Cortisol is the preferred substrate with K_m , 0.80 ± 0.06 μM; V_max , 30.36 ± 1.97 μmol·min^-1; K_cat , 607 ± 39 μmol·μM^-1·min^-1; K_cat /K_m , 760 ± 7.67. Phylogenetic analysis of the 20β-HSDH from B. desmolans suggested that the 20β-HSDH is found in several Bifidobacterium spp, one of which was shown to express 20β-HSDH activity. Notably, we also identified a novel steroid-17,20-desmolase-elaborating bacterium, Propionimicrobium lymphophilum, a normal inhabitant of the urinary tract.

Engineering Mycobacterium smegmatis for testosterone production

A new biotechnological process for the production of testosterone (TS) has been developed to turn the model strain Mycobacterium smegmatis suitable for TS production to compete with the current chemical synthesis procedures. We have cloned and overexpressed two genes encoding microbial 17β‐hydroxysteroid: NADP 17‐oxidoreductase, from the bacterium Comamonas testosteroni and from the fungus Cochliobolus lunatus. The host strains were M. smegmatis wild type and a genetic engineered androst‐4‐ene‐3,17‐dione (AD) producing mutant. The performances of the four recombinant bacterial strains have been tested both in growing and resting‐cell conditions using natural sterols and AD as substrates respectively. These strains were able to produce TS from sterols or AD with high yields. This work represents a proof of concept of the possibilities that offers this model bacterium for the production of pharmaceutical steroids using metabolic engineering approaches.

Mycobacterium smegmatis synthesizes in vitro androgens and estrogens from different steroid precursors

Fast-growing mycobacteria such as Mycobacterium sp. and Mycobacterium smegmatis degrade natural sterols. They are a model to study tuberculosis. Interestingly, M. smegmatis has been found in river effluents derived from paper production, and therefore, it would be important to gain further insight into its capacity to synthesize steroids that are potential endocrine disruptors affecting the development and reproduction of fishes. To our knowledge, the capacity of M. smegmatis to synthesize estrogens and even testosterone has not been previously reported. Therefore, the objective of this study was to investigate the capacity of M. smegmatis to synthesize in vitro testosterone and estrogens from tritiated precursors and to investigate the metabolic pathways involved. Results obtained by thin-layer chromatography showed that 3H-progesterone was transformed to 17OH-progesterone, androstenedione, testosterone, estrone, and estradiol after 6, 12, or 24 h of incubation. 3H-androstenedione was transformed into testosterone and estrogens, mainly estrone, and 3H-testosterone was transformed to estrone and androstenedione. Incubation with 3H-dehydroepiandrosterone rendered androstenediol, testosterone, and estrogens. This ability to transform less potent sex steroids like androstenedione and estrone into other more active steroids like testosterone and estradiol or vice versa suggests that M. smegmatis can influence the amount of self-synthesized strong androgens and estrogens and can transform those found in the environment.

Initial steps in anoxic testosterone degradation by Steroidobacter denitrificans

Steroid compounds have many important physiological activities in higher organisms. Testosterone and related steroids are important environmental contaminants that disrupt the endocrine systems of animals. The degradation of steroids, especially under anoxic conditions, is challenging because of their complex chemical structure. A denitrifying gamma-proteobacterium, Steroidobacter denitrificans, able to grow anaerobically on a variety of steroids as the sole carbon and energy source was adopted as a model organism to study the anoxic degradation of testosterone. We identified the initial intermediates involved in the anoxic testosterone degradation pathway of S. denitrificans. We demonstrated that under anoxic conditions, S. denitrificans initially oxidizes testosterone to 1-dehydrotestosterone, which is then transformed to androsta-1,4-diene-3,17-dione. In addition, it seems that androst-4-en-3,17-dione can also be directly produced from testosterone by S. denitrificans cells. In general, the initial steps of anoxic testosterone degradation by S. denitrificans are similar to those of the oxic pathway demonstrated in Comamonas testosteroni.