Draft genome sequence of soil isolate Mycolicibacterium fortuitum DVD-1301

Some strains of Mycolicibacterium possess high sterol-oxidizing activity and are used in the pharmaceutical industry for the production of steroid precursors. Herein, we report a draft genome sequence of the soil-dwelling Mycolicibacterium fortuitum DVD-1301 isolated in the floodplain of the river Oka. The genome contains a full set of steroid catabolic genes.

De novo transcriptome assembly of Curvularia sp. VKM F-3040, a promising steroid-modifying ascomycete

This research presents de novo transcriptome shotgun assembly for Curvularia sp. VKM F-3040, which is a putative fungal strain able to modify androstane steroids with production of 7-hydroxy and 17-hydroxylated derivatives-key intermediates in the synthesis of pharmaceutical ingredients. The data are of importance for creating novel microbial biocatalysts.

Reconstruction of the Steroid 1(2)-Dehydrogenation System from Nocardioides simplex VKM Ac-2033D in Mycolicibacterium Hosts

Microbial 1(2)-dehydrogenation of 3-ketosteroids is an important basis for the production of many steroid pharmaceuticals and synthons. When using the wild-type strains for whole cell catalysis, the undesirable reduction of the 20-carbonyl group, or 1(2)-hydrogenation, was observed. In this work, the recombinant strains of Mycolicibacterium neoaurum and Mycolicibacterium smegmatis were constructed with blocked endogenous activity of 3-ketosteroid-9α-hydroxylase, 3-ketosteroid-1(2)-dehydrogenase (3-KSD), and expressing 3-KSD encoded by the gene KR76_27125 (kstD2NS) from Nocardioides simplex VKM Ac-2033D. The in vivo activity of the obtained recombinant strains against phytosterol, 6α-methyl-hydrocortisone, and hydrocortisone was studied. When using M. smegmatis as the host strain, the 1(2)-dehydrogenation activity of the constructed recombinant cells towards hydrocortisone was noticeably higher compared to those on the platform of M. neoaurum. A comparison of the strengths of inducible acetamidase and constitutive hsp60 promoters in M. smegmatis provided comparable results. Hydrocortisone biotransformation by M. smegmatis BD/pMhsp_k expressing kstD2NS resulted in 95.4% prednisolone yield, and the selectivity preferred that for N. simplex. Mycolicibacteria showed increased hydrocortisone degradation at 35 °C compared to 30 °C. The presence of endogenous steroid catabolism in Mycolicibacterium hosts does not seem to confer an advantage for the functioning of KstD2NS. The results allow for the evaluation of the prospects for the development of simple technological methods for the selective 1(2)-dehydrogenation of 3-ketosteroids by growing bacterial cells.

Expression of Synthetic cyp102A1-LG23 Gene and Functional Analysis of Recombinant Cytochrome P450 BM3-LG23 in the Actinobacterium Mycolicibacterium smegmatis

Cytochrome CYP102A1 (P450 BM3) of Priestia megaterium (bas. Bacillus megaterium) has several unique functional features and thus provides an ideal object for directed evolution and other synthetic applications. Previously, the CYP102A1-LG23 mutant with 14 mutations in the heme part was obtained that hydroxylates several androstanes at C7β with the formation of products with the anti-inflammatory and neuroprotective activities. In this study, synthetic cyp102A1-LG23 gene encoding the P450 BM3 mutant was expressed as a component of either monocistronic operon or bicistronic operon containing the gdh (glucose dehydrogenase, GDH) or zwf2 (glucose 6-phosphate dehydrogenase, G6PD) gene in Mycolicibacterium smegmatis BD cells. The recombinant bacteria were able hydroxylate androst-4-ene-3,17-dione (AD) into 7β-OH-AD. Their biocatalytic activity was increased twice by increasing the solubility of CYP102A1-LG23 protein in the cells and supplementing the cells with the additional cofactor regeneration system by introducing GDH and G6PD. The maximum 7β-OH-AD yield (37.68 mol%) was achieved by co-expression of cyp102A1-LG23 and gdh genes in M. smegmatis. These results demonstrate the possibility of using synthetic genes to obtain recombinant enzymes and expand our understanding of the processes involved in steroid hydroxylation by bacterial cytochromes. The data obtained can be used to develop new approaches for microbiological production of 7β-hydroxylated steroids in genetically modified Mycolicibacterium species.

Cholesterol Assay Based on Recombinant Cholesterol Oxidase, ABTS, and Horseradish Peroxidase

Cholesterol determination by cholesterol oxidase reaction is a fast, convenient, and highly specific approach with widespread use in clinical diagnostics. Routinely, endpoint measurements with 4-aminophenazone or 4-aminoantipyrine as chromogens and sodium cholate, surfactants, or alcohols as solubilizing agents are used. Here we describe a novel kinetic method to determine cholesterol in 0.05-0.75 mM range in neutral or acidic buffers by use of recombinant cholesterol oxidase from Nocardioides simplex in a coupled reaction with horseradish peroxidase, ABTS as a chromogen, and methyl-β-cyclodextrin as a solubilizing agent.

Selective Microbial Conversion of DHEA into 7α-OH-DHEA

7α-Hydroxy dehydroepiandrosterone (7α-OH-prasterone, 7α-OH-DHEA) is a key steroid intermediate in the synthesis of valuable pharmaceuticals widely used in the treatment of autoimmune illness, rheumatoid arthritis, colitis, and other severe diseases. The steroid can be produced using a filamentous fungus, which is capable of regio- and stereospecific hydroxylation of the steroid 3β-alcohol (DHEA) in the allylic position C7. Here, we describe a method for highly selective microbial production of 7α-OH-DHEA from DHEA using the zygomycete Backusella lamprospora VKM F-944. The method ensures high yield of 7α-OH-DHEA (up to 89%, mol/mol) even at high concentration of the substrate DHEA (15 g/L).

Current Trends and Perspectives in Microbial Bioconversions of Steroids

The microbiological transformation of sterols is currently the technological basis for the industrial production of valuable steroid precursors, the so-called synthons, from which a wide range of steroid and indane isoprenoids are obtained by combined chemical and enzymatic routes. These compounds include value-added corticoids, neurosteroids, sex hormones, bile acids, and other terpenoid lipids required by the medicine, pharmaceutical, food, veterinary, and agricultural industries.Progress in understanding the molecular mechanisms of microbial degradation of steroids, and the development and implementation of genetic technologies, opened a new era in steroid biotechnology. Metabolic engineering of microbial producers makes it possible not only to improve the biocatalytic properties of industrial strains by enhancing their target activity and/or suppressing undesirable activities in order to avoid the formation of by-products or degradation of the steroid core, but also to redirect metabolic fluxes in cells towards accumulation of new metabolites that may be useful for practical applications. Along with whole-cell catalysis, the interest of researchers is growing in enzymatic methods that make it possible to carry out selective structural modifications of steroids, such as the introduction of double bonds, the oxidation of steroidal alcohols, or the reduction of steroid carbonyl groups. A promising area of research is strain engineering based on the heterologous expression of foreign steroidogenesis systems (bacterial, fungal, or mammalian) that ensure selective formation of demanded hydroxylated steroids.Here, current trends and progress in microbial steroid biotechnology over the past few years are briefly reviewed, with a particular focus on the application of metabolic engineering and synthetic biology techniques to improve existing and create new whole-cell microbial biocatalysts.

Obtaining of 24-Norchol-4-ene-3,22-dione from Phytosterol with Mutants of Mycolicibacterium neoaurum

Engineered mutants of Mycolicibacterium spp. are known producers of valuable steroid synthons with C19 or C22 skeleton. Here we describe a method for site-directed mutagenesis of Mycolicibacterium neoaurum strains, bioconversion from phytosterol, and selective purification of C23 steroid 24-norchol-4-ene-3,22-dione (24-NCED) and C22 steroid 20-hydroxymethylpregn-4-ene-3-one (20-HMP). The yields of crystalline products with 95% purity by the method here described are 2.74 ± 0.085 g for 24-NCED and 1.42 ± 0.085 g for 20-HMP from 10 g/L phytosterol. 20-HMP is recognized as the key precursor in chemical syntheses of pharmaceutical corticosteroids and 24-NCED is a promising synthon for the synthesis of valuable steroids and own potent biological activity.

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.

Recombinant Extracellular Cholesterol Oxidase from Nocardioides simplex

Cholesterol oxidase is a highly demanded enzyme used in medicine, pharmacy, agriculture, chemistry, and biotechnology. It catalyzes oxidation of 3β-hydroxy-5-ene- to 3-keto-4-ene- steroids with the formation of hydrogen peroxide. Here, we expressed 6xHis-tagged mature form of the extracellular cholesterol oxidase (ChO) from the actinobacterium Nocardioides simplex VKM Ac-2033D (55.6 kDa) in Escherichia coli cells. The recombinant enzyme (ChO_Ns) was purified using affinity chromatography. ChO_Ns proved to be functional towards cholesterol, cholestanol, phytosterol, pregnenolone, and dehydroepiandrosterone. Its activity depended on the structure and length of the aliphatic side chain at C17 atom of the steroid nucleus and was lower with pregnenolone and dehydroepiandrosterone. The enzyme was active in a pH range of 5.25÷6.5 with the pH optimum at 6.0. Kinetic assays and storage stability tests demonstrated that the characteristics of ChO_Ns were generally comparable with or superior to those of commercial ChO from Streptomyces hygroscopicus (ChO_Sh). The results contribute to the knowledge on microbial ChOs and evidence that ChO from N. simplex VKM Ac-2033D is a promising agent for further applications.

Streptomyces tsukubensis VKM Aс-2618D-an Effective Producer of Tacrolimus

The Streptomyces sp. VKM Ac-2618D strain has been identified, and its morphological and physiological features have been studied in relation to the production of the immunosuppressant tacrolimus. The phenotypic variability of the strain was analyzed, and a dissociant with a high level of tacrolimus production was selected. Based on a comprehensive study of morphological, physiological, and chemotaxonomic properties and on phylogenetic analysis, the strain was named Streptomyces tsukubensis VKM Ac-2618D. The strain genome contains the full version of the tacrolimus biosynthetic gene cluster. The advantages of fed-batch cultivation mode for tacrolimus biosynthesis are shown. The results broaden the understanding of the characteristics of polyketide biosynthesis and can be used in the development of technology for tacrolimus production.

Different genome-wide transcriptome responses of Nocardioides simplex VKM Ac-2033D to phytosterol and cortisone 21-acetate

BACKGROUND

Bacterial degradation/transformation of steroids is widely investigated to create biotechnologically relevant strains for industrial application. The strain of Nocardioides simplex VKM Ac-2033D is well known mainly for its superior 3-ketosteroid Δ1-dehydrogenase activity towards various 3-oxosteroids and other important reactions of sterol degradation. However, its biocatalytic capacities and the molecular fundamentals of its activity towards natural sterols and synthetic steroids were not fully understood. In this study, a comparative investigation of the genome-wide transcriptome profiling of the N. simplex VKM Ac-2033D grown on phytosterol, or in the presence of cortisone 21-acetate was performed with RNA-seq.

RESULTS

Although the gene patterns induced by phytosterol generally resemble the gene sets involved in phytosterol degradation pathways in mycolic acid rich actinobacteria such as Mycolicibacterium, Mycobacterium and Rhodococcus species, the differences in gene organization and previously unreported genes with high expression level were revealed. Transcription of the genes related to KstR- and KstR2-regulons was mainly enhanced in response to phytosterol, and the role in steroid catabolism is predicted for some dozens of the genes in N. simplex. New transcription factors binding motifs and new candidate transcription regulators of steroid catabolism were predicted in N. simplex. Unlike phytosterol, cortisone 21-acetate does not provide induction of the genes with predicted KstR and KstR2 sites. Superior 3-ketosteroid-Δ1-dehydrogenase activity of N. simplex VKM Ac-2033D is due to the kstDs redundancy in the genome, with the highest expression level of the gene KR76_27125 orthologous to kstD2, in response to cortisone 21-acetate. The substrate spectrum of N. simplex 3-ketosteroid-Δ1-dehydrogenase was expanded in this study with progesterone and its 17α-hydroxylated and 11α,17α-dihydroxylated derivatives, that effectively were 1(2)-dehydrogenated in vivo by the whole cells of the N. simplex VKM Ac-2033D.

CONCLUSION

The results contribute to the knowledge of biocatalytic features and diversity of steroid modification capabilities of actinobacteria, defining targets for further bioengineering manipulations with the purpose of expansion of their biotechnological applications.

An Efficient Procedure for the Synthesis of 21-Acetoxypregna-1,4,9(11),16- tetraene-3,20-dione

BACKGROUND

Halogenated corticosteroids are widely used in medicine, and the global need of these steroidal APIs is estimated to be 40 - 70 tons, annually. Vietnam currently imports the pharmaceutical compounds up to 90%, in particular 100% of steroidal drugs. Currently, industrial production is based on the chemical syntheses of corticosteroids from either 16- dehydropregnenolone acetate (obtained from diosgenin) or androstenedione (obtained from phytosterol). The development of shorter synthetic schemes and more economically feasible technologies is of great significance. Introduction of 1(2)-double bond at the final stages of the corticosteroids synthesis results inpoor yield. 21-Acetoxypregna-1,4,9(11),16-tetraene-3,20-dione (tetraene acetate) is a key intermediate in the synthesis of highly active halogenated corticosteroids such as dexamethasone and other halogenated corticosteroids. 21-acetoxypregna-1,4,9(11),16- tetraene-3,20-dione is a key intermediate in the synthesis of dexamethasone from the readily available and cheap 9α-hydroxyandrost-4-ene-3,17-dione.

OBJECTIVE

The purpose of this study was the development of an efficient and shorter procedure for the synthesis of 21-acetoxypregna-1,4,9(11),16-tetraene-3,20-dione from 9α-hydroxyandrostenedione, which is a product of a bio-oxidative degradation of the side chain of phytosterols.

METHODS

Pregnane side chain was constructed using cyanohydrin method. For 1(2)- dehydrogenation, selene dioxide was applied for the introduction of Δ1(2)-double bond. Other stages of the synthesis were epimerization, Stork's iodination procedure and dehydration.

RESULT

21-Acetoxypregna-1,4,9(11),16-tetraene-3,20-dione was prepared from 9α- hydroxyandrostenedione in yield more than 46%.

CONCLUSION

An efficient and practically feasible procedure for the synthesis of 21-acetoxypregna- 1,4,9(11),16-tetraene-3,20-dione from 9α-hydroxyandrostenedione, a key intermediate for the synthesis of 9-haloidated corticoids, has been developed. The procedure can be applied for the production of value-added 9-haloidated corticoids.

Draft Genome Sequence of the Moderately Thermophilic Actinobacterial Steroid-Transforming Saccharopolyspora hirsuta subsp. hirsuta Strain VKM Ac-666T

The draft genome sequence of the type strain Saccharopolyspora hirsuta subsp. hirsuta VKM Ac-666 was sequenced. This moderately thermophilic actinobacterial strain of sugarcane bagasse origin is able to transform different steroid substrates.

Genome-wide response on phytosterol in 9-hydroxyandrostenedione-producing strain of Mycobacterium sp. VKM Ac-1817D

Background

Aerobic side chain degradation of phytosterols by actinobacteria is the basis for the industrial production of androstane steroids which are the starting materials for the synthesis of steroid hormones. A native strain of Mycobacterium sp. VKM Ac-1817D effectively produces 9α-hydroxyandrost-4-ene-3,17-dione (9-OH-AD) from phytosterol, but also is capable of slow steroid core degradation. However, the set of the genes with products that are involved in phytosterol oxidation, their organisation and regulation remain poorly understood.

Results

High-throughput sequencing of the global transcriptomes of the Mycobacterium sp. VKM Ac-1817D cultures grown with or without phytosterol was carried out. In the presence of phytosterol, the expression of 260 genes including those related to steroid catabolism pathways significantly increased. Two of the five genes encoding the oxygenase unit of 3-ketosteroid-9α-hydroxylase (kshA) were highly up-regulated in response to phytosterol (55- and 25-fold, respectively) as well as one of the two genes encoding its reductase subunit (kshB) (40-fold). Only one of the five putative genes encoding 3-ketosteroid-∆¹-dehydrogenase (KstD_1) was up-regulated in the presence of phytosterol (61-fold), but several substitutions in the conservative positions of its product were revealed.

Among the genes over-expressed in the presence of phytosterol, several dozen genes did not possess binding sites for the known regulatory factors of steroid catabolism. In the promoter regions of these genes, a regularly occurring palindromic motif was revealed. The orthologue of TetR-family transcription regulator gene Rv0767c of M. tuberculosis was identified in Mycobacterium sp. VKM Ac-1817D as G155_05115.

Conclusions

High expression levels of the genes related to the sterol side chain degradation and steroid 9α-hydroxylation in combination with possible defects in KstD_1 may contribute to effective 9α-hydroxyandrost-4-ene-3,17-dione accumulation from phytosterol provided by this biotechnologically relevant strain. The TetR-family transcription regulator gene G155_05115 presumably associated with the regulation of steroid catabolism. The results are of significance for the improvement of biocatalytic features of the microbial strains for the steroid industry.

Electronic supplementary material

The online version of this article (10.1186/s12896-019-0533-7) contains supplementary material, which is available to authorized users.

Microbiological synthesis of stereoisomeric 7(α/β)-hydroxytestololactones and 7(α/β)-hydroxytestolactones

Microbiological synthesis of 7α- and 7β-hydroxy derivatives of testololactone and testolactone was developed based on bioconversion of dehydroepiandrosterone (DHEA) by fungus of Isaria fumosorosea VKM F-881 with subsequent modification of the obtained stereoisomers by actinobacteria. The first stage included obtaining of the stereoisomers of 3β,7(α/β)-dihydroxy-17a-oxa-D-homo-androst-5-en-17-ones in the preparative amounts. Then the conversion of 7-hydroxylated D-lactones obtained by selected actinobacteria of Nocardioides simplex VKM Ac-2033D, Saccharopolyspora hirsuta VKM Ac-666, and Streptomyces parvulus MTOC Ac-21v was studied. Under the transformation of 3β,7α-dihydroxy-17a-oxa-D-homo-androst-5-en-17-one and its corresponding 7β-stereoisomer by N. simplex VKM Ac-2033D and S. hirsuta VKM Ac-666 the 7α- and 7β-hydroxy-17a-oxa-D-homo-androst-4-ene-3,17-dione (7α- and 7β-hydroxytestololactone), 7α- and 7β-hydroxy-17a-oxa-D-homo-androsta-1,4-diene-3,17-dione (7α- and 7β-hydroxytestolactone) were obtained with molar yields in a range of 60.3-90.9 mol%. The crystalline products of 7α-hydroxytestololactone, 7α-hydroxytestolactone, and their corresponding 7β-hydroxy stereoisomers were isolated, and their structures were confirmed by mass spectrometry and ¹H-NMR spectroscopy analyses. The strain of Str. parvulus MTOC Ac-21v transformed 3β,7(α/β)-dihydroxy-17a-oxa-D-homo-androst-5-en-17-ones into the corresponding 3-keto-4-ene analogs and did not show 3-ketosteroid 1(2)-dehydrogenase activity. The activity of actinobacteria towards steroid D-lactones was hitherto unreported.The results contribute to the knowledge of metabolic versatility of actinobacteria capable of transforming steroid substrates and may be applied in the synthesis of potential aromatase inhibitors.

Ile351, Leu355 and Ile461 residues are essential for catalytic activity of bovine cytochrome P450scc (CYP11A1)

Cytochrome P450scc (CYP11A1) is a mammalian mitochondrial enzyme which catalyzes cholesterol side chain cleavage to form pregnenolone. Along with cholesterol, some other steroids including sterols with a branched side chain like β-sitosterol are the substrates for the enzyme, but the activity towards β-sitosterol is rather low. Modification of the catalytic site conformation could provide more effective β-sitosterol bioconversion by the enzyme. This study was aimed to find out the amino acid residues substitution of which could modify the conformation of the active site providing possible higher enzyme activity towards β-sitosterol. After structural and bioinformatics analysis three amino acid residues I351, L355, I461 were chosen. Molecular dynamics simulations of P450scc evidenced the stability of the wild type, double (I351A/L355A) and triple (I351A/L355A/I461A) mutants. Mutant variants of cDNA encoding P450scc with the single, double and triple mutations were obtained by site-directed mutagenesis. However, the experimental data indicate that the introduced single mutations Ile351A, Leu355A and Ile461A dramatically decrease the target catalytic activity of CYP11A1, and no activity was observed for double and triple mutants obtained. Therefore, isoleucine residues 351 and 461, and leucine residue 355 are important for the cytochrome P450scc functioning towards sterols both with unbranched (cholesterol) and branched (sitosterol) side chains.

Steroid Bioconversions

Steroid modifications by selected wild-type and engineered strains of microorganisms became an effective tool for the production of high-valued steroidal drugs and their precursors for the pharmaceutical industry. Some microorganisms are effective at the performance of sterol side-chain degradation, oxyfunctionalization of steroid core, and redox reactions at different positions of the steroid molecule. A number of bioprocesses using steroid-transforming microbial strains are well established on an industrial level. Although a range of biocatalytic methods has been developed, selection of suitable microorganisms, as well as creation of new engineered strains, is of great importance for generation of improved bioprocesses and production schemes for obtaining known and new metabolites with potent biological activity. The achievements in genetic and metabolic engineering of steroid-transforming strains in combination with novel approaches in the enzymatic and whole-cell biocatalysis provide a platform for highly effective and selective biotransformations.Here, we briefly review the current state and prospects in the field of microbial bioconversions with special attention to the application of molecular microbiology methods for the generation of new whole cell biocatalysts.

Obtaining of 11α-Hydroxyandrost-4-ene-3,17-dione from Natural Sterols

Two-step one-pot microbial transformation enables obtaining of valuable steroids that are difficult to produce chemically. Here we describe a method for obtaining 11α-hydroxyandrost-4-ene-3,17-dione (11α-HAD) from cheap and available natural sterols (phytosterols or cholesterol).11α-HAD is a primary adrenal steroid in mammals and also a key precursor in the syntheses of halogenated corticoids. Conventional routes for its obtaining are based on chemical synthesis, or microbial hydroxylation of androst-4-ene-3,17-dione (AD). AD in turn is produced primarily with microbial biotransformation of natural sterols by some actinobacteria.Consequent bioconversions of sterols using two microbial strains in one bioreactor vessel without separation and purification of AD provides high yield of 11α-HAD. At the first fermentation step, phytosterol is converted to AD with Mycobacterium neoaurum NRRL 3805B, or relative strains, to yield about 70% (mol/mol). At the second step, AD is almost fully (98%) hydroxylated at the position 11α with Aspergillus ochraceus VKM F-830, or other suitable organisms, in the same bioreactor. At the average, 30% (w/w) of the high-purity crystalline 11α-HAD can be obtained.The method can be exploited for production of 11α-HAD for practical use.

Deoxycholic acid transformations catalyzed by selected filamentous fungi

More than 100 filamentous fungi strains, mostly ascomycetes and zygomycetes from different phyla, were screened for the ability to convert deoxycholic acid (DCA) to valuable bile acid derivatives. Along with 11 molds which fully degraded DCA, several strains were revealed capable of producing cholic acid, ursocholic acid, 12-keto-lithocholic acid (12-keto-LCA), 3-keto-DCA, 15β-hydroxy-DCA and 15β-hydroxy-12-oxo-LCA as major products from DCA. The last metabolite was found to be a new compound. The ability to catalyze the introduction of a hydroxyl group at the 7(α/β)-positions of the DCA molecule was shown for 32 strains with the highest 7β-hydroxylase activity level for Fusarium merismoides VKM F-2310. Curvularia lunata VKM F-644 exhibited 12α-hydroxysteroid dehydrogenase activity and formed 12-keto-LCA from DCA. Acremonium rutilum VKM F-2853 and Neurospora crassa VKM F-875 produced 15β-hydroxy-DCA and 15β-hydroxy-12-oxo-LCA, respectively, as major products from DCA, as confirmed by MS and NMR analyses. For most of the positive strains, the described DCA-transforming activity was unreported to date. The presented results expand the knowledge on bile acid metabolism by filamentous fungi, and might be suitable for preparative-scale exploitation aimed at the production of marketed bile acids.

Genome-wide bioinformatics analysis of steroid metabolism-associated genes in Nocardioides simplex VKM Ac-2033D

Actinobacteria comprise diverse groups of bacteria capable of full degradation, or modification of different steroid compounds. Steroid catabolism has been characterized best for the representatives of suborder Corynebacterineae, such as Mycobacteria, Rhodococcus and Gordonia, with high content of mycolic acids in the cell envelope, while it is poorly understood for other steroid-transforming actinobacteria, such as representatives of Nocardioides genus belonging to suborder Propionibacterineae. Nocardioides simplex VKM Ac-2033D is an important biotechnological strain which is known for its ability to introduce ∆(1)-double bond in various 1(2)-saturated 3-ketosteroids, and perform convertion of 3β-hydroxy-5-ene steroids to 3-oxo-4-ene steroids, hydrolysis of acetylated steroids, reduction of carbonyl groups at C-17 and C-20 of androstanes and pregnanes, respectively. The strain is also capable of utilizing cholesterol and phytosterol as carbon and energy sources. In this study, a comprehensive bioinformatics genome-wide screening was carried out to predict genes related to steroid metabolism in this organism, their clustering and possible regulation. The predicted operon structure and number of candidate gene copies paralogs have been estimated. Binding sites of steroid catabolism regulators KstR and KstR2 specified for N. simplex VKM Ac-2033D have been calculated de novo. Most of the candidate genes grouped within three main clusters, one of the predicted clusters having no analogs in other actinobacteria studied so far. The results offer a base for further functional studies, expand the understanding of steroid catabolism by actinobacteria, and will contribute to modifying of metabolic pathways in order to generate effective biocatalysts capable of producing valuable bioactive steroids.

[Formation of hydroxylated steroid lactones from Dehydroepiandrosterone by Spicaria fumoso-rosea F-881]

The transformation of dehydroepiandrosterone by Spicaria fumoso-rosea VKM F-881 produced 7alpha- and 7beta-hydroxy-dehydroepiandrosterone, 3beta,7alpha-dihydroxy-17a-oxa-D-homo-androst-5-en-17-one, and 3beta,7beta-dihydroxy- 17a-oxa-D-homo-androst-5-en-17-one. The yield of the main product-3beta,7beta-dihydroxy-17a-oxa-D-homo-androst-5-en-17-one-was 49.5-72 mol % at substrate loadings of 5-20 g/L. Lactone formation proceeded through 7alpha- and 7beta-hydroxy derivatives of dehydroepiandrosterone. The structure of the products was determined by mass spectrometry, 1H-NMR spectroscopy, and 13C-NMR spectroscopy. The proposed microbiological method for producing steroid lactones opens prospects for the syn- thesis of novel steroid compounds.

[11beta-Hydroxylation of 6alpha-Fluoro-16alpha-Methyl-Deoxycorticosterone 21-Acetate by filamentous fungi]

Selected filamentous fungi--98 strains of 31 genera--were screened for the ability to catalyze 11beta-hydroxylation of 6alpha-fluoro-16alpha-methyl-deoxycorticosterone 21-acetate (FM-DCA). It was established that representatives of the genera Gongronella, Scopulariopsis, Epicoccum, and Curvularia have the ability to activate 11beta-hydroxylase steroids. The strains of Curvularia lunata VKM F-644 and Gongronella butleri VKM F-1033 expressed maximal activity and formed 6lpha-fluoro-16alpha-methyl-corticosterone as a major bioconversion product from FM-DCA. The structures of the major products and intermediates of the bioconversion were confirmed by TLC, H PLC, MS and 1H NMR analyses. Different pathways of 6alpha-fluoro-16alpha-methyl-corticosterone formation by C. lunata and G. butleri strains were proposed based on intermediate identification. The constitutive character and membrane-binding localization were evidence of a 11beta-hydroxylating system in G. butleri, while an inducible character and microsomal localization was confirmed for 11beta-hydroxylase of C. lunata. Under optimized conditions, the molar yield of 6alpha-fluoro-16alpha-methyl-corticosterone reached 65% at a FM-DCA substrate loading of 6 g/L.

Comparative analysis of genes encoding key steroid core oxidation enzymes in fast-growing Mycobacterium spp. strains

A comparative genome analysis of Mycobacterium spp. VKM Ac-1815D, 1816D and 1817D strains used for efficient production of key steroid intermediates (androst-4-ene-3,17-dione, AD, androsta-1,4-diene-3,17-dione, ADD, 9α-hydroxy androst-4-ene-3,17-dione, 9-OH-AD) from phytosterol has been carried out by deep sequencing. The assembled contig sequences were analyzed for the presence putative genes of steroid catabolism pathways. Since 3-ketosteroid-9α-hydroxylases (KSH) and 3-ketosteroid-Δ(1)-dehydrogenase (Δ(1) KSTD) play key role in steroid core oxidation, special attention was paid to the genes encoding these enzymes. At least three genes of Δ(1) KSTD (kstD), five genes of KSH subunit A (kshA), and one gene of KSH subunit B of 3-ketosteroid-9α-hydroxylases (kshB) have been found in Mycobacterium sp. VKM Ac-1817D. Strains of Mycobacterium spp. VKM Ac-1815D and 1816D were found to possess at least one kstD, one kshB and two kshA genes. The assembled genome sequence of Mycobacterium sp. VKM Ac-1817D differs from those of 1815D and 1816D strains, whereas these last two are nearly identical, differing by 13 single nucleotide substitutions (SNPs). One of these SNPs is located in the coding region of a kstD gene and corresponds to an amino acid substitution Lys (135) in 1816D for Ser (135) in 1815D. The findings may be useful for targeted genetic engineering of the biocatalysts for biotechnological application.

Hydroxylation of lithocholic acid by selected actinobacteria and filamentous fungi

Selected actinobacteria and filamentous fungi of different taxonomy were screened for the ability to carry out regio- and stereospecific hydroxylation of lithocholic acid (LCA) at position 7β. The production of ursodeoxycholic acid (UDCA) was for the first time shown for the fungal strains of Bipolaris, Gibberella, Cunninghamella and Curvularia, as well as for isolated actinobacterial strains of Pseudonocardia, Saccharothrix, Amycolatopsis, Lentzea, Saccharopolyspora and Nocardia genera. Along with UDCA, chenodeoxycholic (CDCA), deoxycholic (DCA), cholic (CA), 7-ketodeoxycholic and 3-ketodeoxycholic acids were detected amongst the metabolites by some strains. A strain of Gibberella zeae VKM F-2600 expressed high level of 7β-hydroxylating activity towards LCA. Under optimized conditions, the yield of UDCA reached 90% at 1g/L of LCA and up to 60% at a 8-fold increased substrate loading. The accumulation of the major by-product, 3-keto UDCA, was limited by using selected biotransformation media.

Microbial steroid transformations: current state and prospects

Studies of steroid modifications catalyzed by microbial whole cells represent a well-established research area in white biotechnology. Still, advances over the last decade in genetic and metabolic engineering, whole-cell biocatalysis in non-conventional media, and process monitoring raised research in this field to a new level. This review summarizes the data on microbial steroid conversion obtained since 2003. The key reactions of structural steroid functionalization by microorganisms are highlighted including sterol side-chain degradation, hydroxylation at various positions of the steroid core, and redox reactions. We also describe methods for enhancement of bioprocess productivity, selectivity of target reactions, and application of microbial transformations for production of valuable pharmaceutical ingredients and precursors. Challenges and prospects of whole-cell biocatalysis applications in steroid industry are discussed.

Cholesterol oxidase ChoD is not a critical enzyme accounting for oxidation of sterols to 3-keto-4-ene steroids in fast-growing Mycobacterium sp. VKM Ac-1815D

Fast-growing strain of Mycobacterium sp. VKM Ac-1815D is capable of effective oxidizing of sterols (phytosterol, cholesterol, ergosterol) to androstenedione and other valuable 3-oxo-steroids. To elucidate the role of cholesterol oxidase in sterol catabolism by the strain, the choD gene has been cloned and sequenced. The deduced gene product (M(r) 63.5kDa) showed homologies over its entire length to a large number of proteins belonging to the InterPro-family EPR006076, which includes various FAD dependent oxidoreductases. The expression of choD in Escherichia coli was shown to result in the synthesis of membrane associated cholesterol oxidase. In addition to cholesterol, the enzyme oxidized β-sitosterol, dehydroepiandrosterone, ergosterol, pregnenolone, and lithocholic acid. Knock-out of choD in Mycobacterium sp. VKM Ac-1815D strain was obtained by the gene replacement technique. The mutant strain transformed sitosterol forming exclusively 3-keto-4-ene steroids with androstenedione as a major product, thus evidencing that choD knock out did not abrogate sterol A-ring oxidation. The results indicated that ChoD is not a critical enzyme responsible for modification of 3β-hydroxy-5-ene- to 3-keto-4-ene steroids in Mycobacterium sp. VKM Ac-1815D. Article from a special issue on steroids and microorganisms.

Microbial side-chain degradation of ergosterol and its 3-substituted derivatives: a new route for obtaining of deltanoids

The strain of Mycobacterium sp. VKM Ac-1815D was found to convert ergosterol and its 3-acetate mainly to androst-4-ene-3,17-dione (AD) thus demonstrating ability to reduce 7(8)-double bond and hydrolyze sterol ester in addition to oxidation of 3beta-hydroxy group, Delta(5)-Delta(4) isomerization and side-chain degradation. Ergosterol bioconversion in the presence of isoflavones and ions of some bivalent metals - known inhibitors of 3beta-hydroxysteroid dehydrogenase, did not alter products composition. Protection of ergosterol 3beta-hydroxyl with methoxymethyl group allowed the formation of bioconversion products retaining the Delta(5,7)-configuration. The major product was identified by mass-spectrometry and proton NMR as 3-methoxymethoxy-androsta-5,7-diene-17-one (MA). The MA producing activity was found to be inducible with sterols, cholestenone or lithocholic acid, but not with dehydroepiandrosterone, AD, androsta-1,4-ene-3,17-dione or organic acids. Under the optimized conditions, the yield of MA reached 5g/l from 10g/l O-methoxymethyl-ergosterol (approx. 60% molar conversion) for 120h. The results might be applied at the production of novel vitamin D derivatives.

[Bioconversion of C19- and C21-steroids with parent and mutant strains of Curvularia lunata]

Regio- and stereospecificity of microbial hydroxylation was studied at the transformation of 3-keto-4-ene steroids of androstane and pregnane series by the filamentous fungus of Curvularia lunata VKMF-644. The products of the transformations were isolated by column chromatography and identified using HPLC, mass-spectrometry (MS) and proton nuclear magnetic resonance (1H NMR) analyses. Androst-4-ene-3,17-dione (AD) and its 1(2)-dehydro- and 9alpha-hydroxylated (9-OH-AD) derivatives were hydroxylated by the fungus mainly in position 14alpha, while 6alpha-, 6beta- and 7alpha-hydroxylated products were revealed in minor amounts. At the transformation of C21-steroids (cortexolone and its acetylated derivatives) the presence of 17-acetyl group was shown to facilitate further selectivity of 11beta-hydroxylation. Original procedures for protoplasts obtaining, mutagenesis and mutant strain selection have been developed. A stable mutant (M4) of C. lunata with high 11beta-hydroxylase activity towards 21-acetate and 17alpha,21-diacetate of cortexolone was obtained. Yield of 11beta-hydroxylated products reached about 90% at the transformation of 17alpha, 21-diacetate of cortexolone using mutant strain M4.

[Dihydroxylation of dehydroepiandrosterone in positions 7alpha and 15alpha by mycelial fungi]

The ability of 485 fungal strains is studied for catalysis of the process of 7alpha, 15alpha-dihydroxylation of dehydroepiandrosterone (DHEA, 3alpha-hydroxy-5-androstene-17-one), a key intermediate of the synthesis of physiologically active compounds. The ability for the formation of 3alpha, 7alpha, 15alpha-trihydoxy-5-androstene-17-one (7alpha, 15alpha-di-OH-DHEA) was found for the first time for representatives of 12 genera, eight families, and six orders of ascomycetes, eight genera, four families, and one order of zygomycetes, one genus, one family, and one order of basidiomycetes, and four genera of mitosporous fungi. The most active strains are found among genera Acremonium, Gibberella, Fusarium, and Nigrospora. In the process of transformation of DHEA (2 g/l) by strains of Fusarium oxysporum RKM F-1600 and FGibberella zeae BKM F-2600, the molar yield was 63 and 68%, respectively. Application of the revealed active strains of microorganisms opens prospects for the efficient production of key intermediates of synthesis of modern medical preparations.

Synthesis of 3beta-hydroxy-androsta-5,7-dien-17-one from 3beta-hydroxyandrost-5-en-17-one via microbial 7alpha-hydroxylation

The synthesis of 3beta-hydroxy-androsta-5,7-dien-17-one from 3beta-hydroxy-androst-5-en-17-one (dehydroepiandrosterone, DHEA) via microbial 7alpha-hydroxylation has been accomplished. At the first stage, 3beta,7alpha-dihydroxy-androst-5-en-17-one was obtained in high yield (71.2%) using a strain of Gibberella zeae VKM F-2600, which was first applied for DHEA conversion. The further route included the substitution of 7alpha-hydroxyl group with chlorine followed by a dehydrochlorination stage, and required minimal purifications of the intermediate products. The steroids obtained at every step were characterized by TLC,1H NMR, MS, UV- and IR-spectrometry. The combination of microbial and chemical steps ensured 54.6% yield of the target 3beta-hydroxy-androsta-5,7-dien-17-one from DHEA and can be applied for obtaining novel vitamin D derivatives.

Methyl-beta-cyclodextrin alters growth, activity and cell envelope features of sterol-transforming mycobacteria

Modified beta-cyclodextrins have been shown previously to enhance sterol conversion to 4-androstene-3,17-dione (AD) and 1,4-androstadiene-3,17-dione (ADD) by growing Mycobacterium spp. The enhancement effect was mainly attributed to steroid solubilization by the formation of inclusion complexes with modified cyclodextrins. In this work, the influence of randomly methylated beta-cyclodextrin (MCD) on the growth, AD- and ADD-producing activity, cell wall (CW) composition and ultrastructure of sterol-transforming Mycobacterium sp. VKM Ac-1816D was studied. The specific growth rate of the strain on glycerol increased in the presence of MCD (20-100 mM). Washed cells grown in the presence of MCD (20-40 mM) expressed 1.6-fold higher ADD-producing activity than did the cells grown without MCD, and their adhesiveness differed. Electron microscopy showed MCD-mediated CW exfoliation and accumulation of membrane-like structures outside the cells, while preserving cells intact. The analysis of CW composition revealed both a decrease in the proportion of extractable lipids and a considerable shift in fatty acid profile resulting from MCD action. The MCD-mediated enhancement of mycolic and fatty acids content was observed outside the cells. The total secreted protein level rose 2.4-fold, and the extracellular 3-hydroxysteroid oxidase activity 3.2-fold. The composition of the CW polysaccharide was not altered, while the overall proportion of the carbohydrates in the CW of the MCD-exposed mycobacteria increased. The results showed that the multiple mechanisms of MCD-mediated intensification of sterol to AD(D) conversion by mycobacteria include not only solubilization of steroids, but also the increase of CW permeability for both steroids and soluble nutrients, disorganization of the lipid bilayer and the release of steroid-transforming enzymes weakly associated with the CW.

Steroid-1-dehydrogenase of Mycobacterium sp. VKM Ac-1817D strain producing 9α-hydroxy-androst-4-ene-3,17-dione from sitosterol

The strain of Mycobacterium sp. VKM Ac-1817D forms 9alpha-hydroxy-androst-4-ene-3,17-dione (9-OH-AD) as a major product from sitosterol. The formation of 9-OH-AD was accompanied with its partial destruction due to residual steroid-1-dehydrogenase (St1DH) activity. The activity was found to be induced by androst-4-ene-3,17-dione (AD), while other intermediates of sitosterol oxidation did not influence 1(2)-dehydrogenation. The enzyme is located mainly in the cytosolic fraction. The cytosolic St1DH (dimer, M (r) approximately 58 kDa) was partially purified by ammonium sulfate fractionation, ion-exchange chromatography on DEAE-Sepharose and Phenyl-Sepharose, and gel filtration on Bio-Gel A-0.5M. It expressed the St1DH activity toward both AD and 9-OH-AD.

[Transformation of steroids by actinobacteria: a review]

Development of pharmaceutical industry is currently aimed at introducing biotechnological processes on a large-scale and thereby replacing multiple-stage chemical syntheses. Actinobacteria are efficient biocatalysts of many processes involving steroid bioconversion, which hold considerable importance for the synthesis of hormonal drugs. The potential to catalyze the conversion of a broad spectrum of steroid substrates makes it possible to expect efficient utilization of these microorganisms in development of new technologies of manufacturing steroid pharmaceutical substances. The review is a first attempt to systematize data on the potential of actinobacteria to catalyze diverse reactions of steroid transformation (such as hydroxylation, introduction and reduction of double bonds, oxidation of steroid alcohols, reduction of ketones, side chain de-esterification and degradation, etc.), with emphasis on processes of practical biotechnological importance and progress in steroid bioconversion over the last ten years.

[Enzymes involved in modification of the steroid nucleus of industrial mycobacterial strains: isolation, functions, and properties]

The key enzymes involved in modification of the steroid nucleus of sterol-transforming mycobacteria--3beta-hydroxysteroid oxidase (3-OH-SO, EC 1.13.1.2) and 17beta-hydroxysteroid dehydrogenase (17-OH-SDH, EC 1.1.1)--were isolated and characterized. It is shown that 3-OH-SO is a multifunctional enzyme catalyzing oxidation of the 3beta-OH group, delta5 --> delta4 isomerization, and 6-hydroxylation. Two forms of intracellular 17-OH-SDH that catalyze redox reactions at C17 were found, and their properties were determined. The presence of an extracellular 17-OH-SDH in Mycobacterium spp. (VKM Ac-1815 D and Et1) was demonstrated for the first time.

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

The localization of mycobacterial 17beta-hydroxysteroid dehydrogenase (17beta-OH SDH) was studied using cell fractionation and cytochemical investigation. Mycobacterium sp. Et1 mutant strain derived from Mycobacterium sp. VKM Ac-1815D and characterized by increased 17beta-OH SDH activity was used as a model organism. Subcellular distribution study showed both soluble and membrane-bound forms of mycobacterial 17beta-hydroxysteroid dehydrogenase. The cytochemical method based on a copper ferrocyanide procedure followed by electron microscopic visualization was applied in order to investigate the intracellular localization of bacterial 17beta-OH SDH in more detail. The enzyme was found to be located in the peripheral cytoplasmic zone adjoining the cytoplasmic membrane (CM). 17beta-OH SDH was loosely membrane bound and easily released into the environment under the cell integrity failure.

Mycobacterium sp. mutant strain producing 9α-hydroxyandrostenedione from sitosterol

Mycobacterium sp. VKM Ac-1815D and its derivatives with altered resistance to antibacterial agents were able to produce androst-4-ene-3,17-dione (AD) as a major product from sitosterol. In this study, those strains were subjected to subsequent mutagenization by chemical agents and UV irradiation in combination with sitosterol selection pressure. The mutant Mycobacterium sp. 2-4 M was selected, being capable of producing 9alpha-hydroxyandrost-4-ene-3,17-dione (9-OH-AD) as a major product from sitosterol, with a 50% molar yield. Along with 9-OH-AD, both AD and 9alpha-hydroxylated metabolites with a partially degraded side-chain were formed from sitosterol by the mutant strain. The strain was unable to degrade 9-OH-AD, but degraded androsta-1,4-diene-3,17-dione (ADD), thus indicating a deficiency in steroid 1(2)-dehydrogenase and the presence of 9alpha-hydroxylase activity.

Extracellular 3beta-hydroxysteroid oxidase of Mycobacterium vaccae VKM Ac-1815D

Extracellular 3beta-hydroxysteroid oxidase (SO) has been isolated from cell-free cultivation broth at the growth of Mycobacterium vaccae VKM Ac-1815D on glycerol-mineral medium in the presence of sitosterol. The enzyme is responsible for the transformation of 3beta-hydroxy-5-ene- to 3-keto-4-ene-moiety of steroids including dehydrogenation of 3beta-hydroxy function followed by delta5-->delta4 isomerization. 6-Hydroxy-4-sitosten-3-one and 6-hydroxy-4-androsten-3,17-dione were revealed among the metabolites at the incubation of the enzyme preparations with sitosterol and dehydroepiandrosterone (DHEA), respectively. The enzyme was strongly NADH or NADPH dependent. SO has been purified over 300-fold using cultivation broth concentration on hollow fibers followed by fractionation by ammonium sulphate, column chromatography on DEAE-Toyopearl, hydroxyapatite Bio-Gel HTP and double gel-filtration on Bio-Gel A 0.5 M. SDS-electrophoresis gave a molecular mass estimate of 62 +/- 4 kDa. The purified SO obeyed Michaelis-Menten kinetics, double reciprocal plots kinetics revealed Km value towards DHEA 5 x 10(-4) M. Along with SO activity, 17-hydroxysteroid dehydrogenase (17-OH SDH) and 3-ketosteroid-1(2)-dehydrogenase (1(2)-SDH) activities were detected in cell-free cultivation broth. The extracellular steroid transforming activities of C-17-ketosteroid producing mycobacteria were hitherto unreported.

Hydroxylation of carbazoles by Aspergillus flavus VKM F-1024

Carbazole was metabolized by Aspergillus flavus VKM F-1024 forming few monohydroxylated products. The structure of metabolites was determined by TLC, GC, MS and (1)H NMR analyses. 3-Hydroxycarbazole was revealed as a major bioconversion product, 1-hydroxy- and 2-hydroxycarbazoles were observed as minor products. In the presence of 1-benzoylindole, the hydroxylation position shifted toward preferable accumulation of 2-hydroxycarbazole and the formation of 2,6- and 2,7-dihydroxycarbazoles. This effect and microbial formation of these metabolites have never been reported before. At the conversion of N-acetyl- and N-benzoylcarbazoles, carbazole was the major product, while 1-, 2- and 3-monohydroxycarbazoles were formed in small amounts.

21-Acetoxy-pregna-4(5),9(11),16(17)-triene-21-ol-3,20-dione conversion by Nocardioides simplex VKM Ac-2033D

The conversion of 21-acetoxy-pregna-4(5),9(11),16(17)-triene-21-ol-3,20-dione (I) by Nocardioides simplex VKM Ac-2033D was studied purposed selective production of its 1(2)-dehydroanalogues-value precursors in the synthesis of modern glucocorticoids starting from 9alpha-hydroxyandrostenes. 21-Acetoxy-pregna-1(2),4(5),9(11),16(17)-tetraene-21-ol-3,20-dione (II), pregna-4(5),9(11),16(17)-triene-21-ol-3,20-dione (III) and pregna-1(2),4(5),9(11),16(17)-tetraene-21-ol-3,20-dione (IV) were revealed as metabolites, and the structures were confirmed by mass spectrometry and (1)H nuclear magnetic resonance (NMR) spectroscopy. The metabolic pathways of I by N. simplex included 1(2)-dehydrogenation and deacetylation. The sequence of the reactions was shown to depend on the transformation conditions. The presence of both soluble and membrane associated steroid esterases in N. simplex was demonstrated using cell fractionation. Unlike inducible 1(2)-dehydrogenase, steroid esterase was shown to be constitutive. The conditions providing selective accumulation of II from I by whole N. simplex cells were determined.