Microbial transformations of steroids--XII. Progesterone hydroxylation profiles are modulated by post-translational modification of an electron transfer protein in Streptomyces roseochromogenes

Actinobacteria as Microbial Cell Factories and Biocatalysts in The Synthesis of Chiral Intermediates and Bioactive Molecules; Insights and Applications

Actinobacteria are one of the most intriguing bacterial phyla in terms of chemical diversity and bioactivities of their reported biomolecules and natural products, including various types of chiral molecules. Actinobacterial genera such as Detzia, Mycobacterium, and Streptomyces are among the microbial sources targeted for selective reactions such as asymmetric biocatalysis catalyzed by whole cells or enzymes induced in their cell niche. Remarkably, stereoselective reactions catalyzed by actinobacterial whole cells or their enzymes include stereoselective oxidation, stereoselective reduction, kinetic resolution, asymmetric hydrolysis, and selective transamination, among others. Species of actinobacteria function with high chemo-, regio-, and enantio-selectivity under benign conditions, which could help current industrial processing. Numerous selective enzymes were either isolated from actinobacteria or expressed from actinobacteria in other microbes and hence exploited in the production of pure organic compounds difficult to obtain chemically. In addition, different species of actinobacteria, especially Streptomyces species, function as natural producers of chiral molecules of therapeutic importance. Herein, we discuss some of the most outstanding contributions of actinobacteria to asymmetric biocatalysis, which are important in the organic and/or pharmaceutical industries. In addition, we highlight the role of actinobacteria as microbial cell factories for chiral natural products with insights into their various biological potentialities.

Reviewing a plethora of oxidative-type reactions catalyzed by whole cells of Streptomyces species

Selective oxidation reactions represent a challenging task for conventional organic chemistry. Whole-cell biocatalysis provides a very convenient, easy to apply method to carry out different selective oxidation reactions including chemo-, regio-, and enantio-selective reactions. Streptomyces species are important biocatalysts as they can catalyze these selective reactions very efficiently owing to the wide diversity of enzymes and enzymatic cascades in their cell niche. In this review, we present and analyze most of the examples reported to date of oxidative reactions catalyzed by Streptomyces species as whole-cell biocatalysts. We discuss 33 different Streptomyces species and strains and the role they play in different oxidative reactions over the past five decades. The oxidative reactions have been classified into seven categories that include: hydroxylation of steroids/non-steroids, asymmetric sulfoxidations, oxidation of aldehydes, multi-step oxidations, oxidative cleavage, and N-oxidations. The role played by Streptomyces species as recombinant hosts catalyzing bio-oxidations has also been highlighted.

Biotechnological Transformation of Hydrocortisone into 16α-Hydroxyprednisolone by Coupling Arthrobacter simplex and Streptomyces roseochromogenes

16α-Hydroxyprednisolone, an anti-inflammatory drug, could be potentially obtained from hydrocortisone bioconversion by combining a 1,2-dehydrogenation reaction performed by Arthrobacter simplexATCC31652 with a 16α-hydroxylation reaction by Streptomyces roseochromogenes ATCC13400. In this study we tested, for the first time, potential approaches to couple the two reactions using similar pH and temperature conditions for hydrocortisone bioconversion by the two strains. The A. simplex capability to 1,2-dehydrogenate the 16α-hydroxyhydrocortisone, the product of S. roseochromogenes transformation of hydrocortisone, and vice versa the capability of S. roseochromogenes to 16α-hydroxylate the prednisolone were assessed. Bioconversions were studied in shake flasks and strain morphology changes were observed by SEM. Whole cell experiments were set up to perform the two reactions in a sequential mode in alternate order or contemporarily at diverse temperature conditions. A. simplex catalyzed either the dehydrogenation of hydrocortisone into prednisolone efficiently or of 16α-hydroxyhydrocortisone into 16α-hydroxyprednisolone in 24 h (up to 93.9%). Surprisingly S. roseochromogenes partially converted prednisolone back to hydrocortisone. A 68.8% maximum of 16α-hydroxyprednisolone was obtained in 120-h bioconversion by coupling whole cells of the two strains at pH 6.0 and 26 °C. High bioconversion of hydrocortisone into 16α-hydroxyprednisolone was obtained for the first time by coupling A. simplex and S. roseochromogenes.

Screening for strains with 11α-hydroxylase activity for 17α-hydroxy progesterone biotransformation

Various corticosteroids are prepared by using 11α,17α-diOH-progesterone (11α,17α-diOH-PROG) as an important intermediate and raw material. Hence, strains that can improve the yields of 11α,17α-diOH-PROG should be screened. Cunninghamella elegans CICC40250 was singled out from five common 11α hydroxylation strains. The reaction parameters of 11α,17α-diOH-PROG production were also investigated. C. elegans CICC40250 could efficiently catalyze the hydroxylation of 17α-hydroxy progesterone (17α-OH-PROG) at C-11α position. This strain could also effectively convert 11α,17α-diOH-PROG at high substrate concentrations (up to 30g/L). After the coenzyme precursor glucose was added, the rate of 11α,17α-diOH-PROG formation reached 84.2%, which was 11.4% higher than that of the control group. Our study established a simple and feasible mechanism to increase 11α,17α-diOH-PROG production levels. This mechanism involves C. elegans CICC40250 that can be efficiently applied to induce the biotransformation of 17α-OH-PROG with a hydroxylation biocatalytic ability.

Biocatalyst-mediated production of 11,15-dihydroxy derivatives of androst-1,4-dien-3,17-dione

Hydroxylation of steroids at various positions is a powerful tool for the production of valuable pharmaceutical ingredients and precursors. Our paper reported the synchronous dihydroxylation of an efficient strain, i.e., Colletotrichum lini AS3.4486, at two points. C. lini AS3.4486 was selected from 10 strains; this strain can catalyze the dihydroxylation of androst-1,4-dien-3,17-dione at C-11α and C-15α positions. Transformation of ADD(I) by C. lini AS3.4486 produced metabolites II-IV. The structures of these compounds were elucidated by liquid chromatography-mass spectrometry (LC-MS), Fourier Transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and X-ray as 15-hydroxyandrost-1,4-dien-3,17-dione (15α-OH-ADD; II), 11,15-dihydroxyandrost-1,4-dien-3,17-dione (11,15-diOH-ADD; III), and 15,17β-dihy-droxyandrost-1,4-dien-3-one (15-OH-BD; BD is the abbreviation of boldenone; IV). III, as a novel compound, was reported for the first time. The course of conversion and mechanism about dihydroxylation reaction was also investigated. On the basis of time course analysis of hydroxylation, I underwent regioselective hydroxylation at 15 position and was subsequently converted to III and IV. Enzyme inhibition analysis showed that 11- and 15-hydroxylations were catalyzed by different hydroxylases. The effect of substrate concentration on I transformation was also determined. Results showed that the optimum concentration of I was 20 g/L, and the yield of III was up to 18.8 g/L.

Biotechnological transformation of hydrocortisone to 16α-hydroxy hydrocortisone by Streptomyces roseochromogenes

Streptomyces roseochromogenes is able to hydroxylate steroid compounds in different positions of their cycloalkane rings thanks to a cytochrome P-450 multi-enzyme complex. In this paper, the hydroxylation of the hydrocortisone in the 16α position, performed by bacterial whole cells, was investigated in both shake flask and fermentation conditions; the best settings for both cellular growth and transformation reaction were studied by investigating the optimal medium composition, the kinetic of conversion, the most suitable substrate concentration and the preferred addition timing. Using newly formulated malt extract- and yeast extract-based media, a 16α-hydrohydrocortisone concentration of 0.2 ± 0.01 g L(-1) was reached in shake flasks. Batch experiments in a 2-L fermentor established the reproducibility and robustness of the biotransformation, while a pulsed batch fermentation strategy allowed the production to increase up to 0.508 ± 0.01 g L(-1). By-product formation was investigated, and two new derivates of the hydrocortisone obtained during the bacterial transformation reaction and unknown so far, a C-20 hydroxy derivate and a C-21 N-acetamide one, were determined by NMR analyses.

Studies on Bacillus stearothermophilus. Part II. Transformation of progesterone

Bacillus stearothermophilus, a thermophilic bacterium isolated from Kuwaiti desert, when incubated with exogenous progesterone for 10 days at 65 degrees C produced two new dihydroxy isomers of progesterone, and two known compounds, 5 alpha-pregnane-3,6,20-trione and 6-dehydroprogesterone, along with the earlier reported monohydroxylated metabolites and a B-Seco compound. The two new dihydroxy compounds were identified as 6 alpha,20 alpha-dihydroxyprogesterone and 6 beta,20 alpha-dihydroxyprogesterone. These metabolites were purified by TLC and HPLC followed by their identification through 1H, 13C NMR and other spectroscopic data.

Studies on Bacillus stearothermophilus. Part 1. Transformation of progesterone to a new metabolite 9,10-seco-4-pregnene-3,9,20-trione

When Bacillus stearothermophilus, a thermophilic bacterium isolated from the Kuwaiti desert, was incubated with exogenous progesterone for 24 h, three monohydroxylated metabolites were produced. 20alpha-Hydroxyprogesterone was the major metabolite produced in 60.8 relative percentage yield. The other two monohydroxylated metabolites were identified as 6beta-hydroxyprogesterone and the rare 6alpha-hydroxyprogesterone in 21.0 and 13.6 relative percentage yields, respectively. A new metabolite 9,10-seco-4-pregnene-3,9,20-trione was isolated in 3.7 relative percentage yield. All metabolites were purified by preparative TLC and HPLC followed by their identification using 1H, 13C NMR and other spectroscopic data.