Search Results (8)

This research aimed at obtaining new derivatives of pregn-1,4-diene-3,20-dione (Δ¹-progesterone) (2) through microbiological transformation. For the role of catalysts, we used six strains of entomopathogenic filamentous fungi (Beauveria bassiana KCh J1.5, Beauveria caledonica KCh J3.3, Isaria fumosorosea KCh J2, Isaria farinosa KCh KW1.1, Isaria tenuipes MU35, and Metarhizium robertsii MU4). The substrate (2) was obtained by carrying out an enzymatic 1,2-dehydrogenation on an increased scale (3.5 g/L) using a recombinant cholest-4-en-3-one Δ¹-dehydrogenase (AcmB) from Sterolibacterium denitrificans. All selected strains were characterized by the high biotransformation capacity for the used substrate. As a result of the biotransformation, six steroid derivatives were obtained: 11α-hydroxypregn-1,4-diene-3,20-dione (3), 6β,11α-dihydroxypregn-1,4-diene-3,20-dione (4), 6β-hydroxypregn-1,4-diene-3,11,20-trione (5), 6β,17α-dihydroxypregn-1,4-diene-3,20-dione (6), 6β,17β-dihydroxyandrost-1,4-diene-3-one (7), and 12β,17α-dihydroxypregn-1,4-diene-3,20-dione (8). The results show evident variability of the biotransformation process between strains of the tested biocatalysts from different species described as entomopathogenic filamentous fungi. The obtained products were tested in silico using cheminformatics tools for their pharmacokinetic and pharmacodynamic properties, proving their potentially high biological activities. This study showed that the obtained compounds may have applications as effective inhibitors of testosterone 17β-dehydrogenase. Most of the obtained products should, also with a high probability, find potential uses as androgen antagonists, a prostate as well as menopausal disorders treatment. They should also demonstrate immunosuppressive, erythropoiesis-stimulating, and anti-inflammatory properties. Full article

As a novel reaction mode of oxidative dehydrogenation of ethane to ethylene, the chemical looping oxidative dehydrogenation (CL-ODH) of ethane to ethylene has attracted much attention. Instead of using gaseous oxygen, CL-ODH uses lattice oxygen in an oxygen carrier or redox catalyst to facilitate the ODH reaction. In this paper, a perovskite type redox catalyst LaMnO_3+δ was used as a substrate, Ce³⁺ with different proportions was introduced into its A site, and its CL-ODH reaction performance for ethane was studied. The results showed that the ratio of Mn⁴⁺/Mn³⁺ on the surface of Ce-modified samples decreased significantly, and the lattice oxygen species in the bulk phase increased; these were the main reasons for improving ethylene selectivity. La_0.7Ce_0.3MnO₃ showed the best performance during the ODH reaction and showed good stability in twenty redox cycle tests. Full article

Bacteria and fungi that are able to metabolize steroids express 3-ketosteroid-Δ¹-dehydrogenases (KstDs). KstDs such as AcmB form Sterolibacterium denitrificans Chol-1 catalyze the enantioselective 1α,2β-dehydrogenation of steroids to their desaturated analogues, e.g., the formation of 1,4-androstadiene-3,17-dione (ADD) from 4-androsten-3,17-dione (AD). The reaction catalyzed by KstD can be reversed if the appropriate electron donor, such as benzyl viologen radical cation, is present. Furthermore, KstDs can also catalyze transhydrogenation, which is the transfer of H atoms between 3-ketosteroids and 1-dehydrosteroids. In this paper, we showed that AcmB exhibits lower pH optima for hydrogenation and dehydrogenation by 3.5–4 pH units than those observed for KstD from Nocardia corallina. We confirmed the enantiospecificity of 1α,2β-hydrogenation and 1α,2β-transhydrogenation catalyzed by AcmB and showed that, under acidic pH conditions, deuterons are introduced not only at 2β but also at the 1α position. We observed a higher degree of H/D exchange at Y363, which activates the C2-H bond, compared to that at FAD, which is responsible for redox at the C1 position. Furthermore, for the first time, we observed the introduction of the third deuteron into the steroid core. This effect was explained through a combination of LC-MS experiments and QM:MM modelling, and we attribute it to a decrease in the enantioselectivity of C2-H activation upon the deuteration of the 2β position. The increase in the activation barrier resulting from isotopic substitution increases the chance of the formation of d³-substituted 3-ketosteroids. Finally, we demonstrate a method for the synthesis of 3-ketosteroids chirally deuterated at 1α,2β positions, obtaining 1α,2β-d²-4-androsten-3,17-dione with a 51% yield (8.61 mg). Full article

3-Ketosteroid-Δ¹-dehydrogenases (KstDs [EC 1.3.99.4]) catalyze the Δ¹-dehydrogenation of steroids and are a class of important enzymes for steroid biotransformations. In this study, nine putative kstD genes from different origins were selected and overexpressed in Escherichia coli BL21(DE3). These recombinant enzymes catalyzed the Δ¹-desaturation of a variety of steroidal compounds. Among them, the KstD from Propionibacterium sp. (PrKstD) displayed the highest specific activity and broad substrate spectrum. The detailed catalytic characterization of PrKstD showed that it can convert a wide range of 3-ketosteroid compounds with diverse substituents, ranging from substituents at the C9, C10, C11 and C17 position through substrates without C4-C5 double bond, to previously inactive C6-substituted ones such as 11β,17-dihydroxy-6α-methyl-pregn-4-ene-3,20-dione. Reaction conditions were optimized for the biotransformation of hydrocortisone in terms of pH, temperature, co-solvent and electron acceptor. By using 50 g/L wet resting E. coli cells harboring PrKstD enzyme, the conversion of hydrocortisone was about 92.5% within 6 h at the substrate concentration of 80 g/L, much higher than the previously reported results, demonstrating the application potential of this new KstD. Full article

Catalytic dehydrogenation coupling of methane (DCM) represents an effective way to convert natural gas to more useful C₂ products (C₂H₆, C₂H₄). In this work, BaCe_0.85Tb_0.05Co_0.1O_3-δ (BCTCo) perovskite hollow fiber membranes were fabricated by the combined phase inversion and sintering method. SrCe_0.95Yb_0.05O_3-δ (SCYb) perovskite oxide was loaded as a catalyst onto the inner hollow fiber membrane surface, which promoted the CH₄ conversion and the C₂ hydrocarbon selectivity during the DCM reaction. The introduction of steam into the methane feed gas mixture elevated the C₂ selectivity and yield due to the alleviation of coke deposition. Switching N₂ to air as the sweep gas further increased the C₂ selectivity and yield. However, the conversion of methane was limited by both the low permeability of the membrane and the insufficient catalytic activity of the catalyst, leading to low C₂ yield. Full article

Cholest-4-en-3-one Δ¹-dehydrogenase (AcmB) from Sterolibacterium denitrificans was successfully immobilized on 3-aminopropyltrimethoysilane functionalized mesoporous cellular foam (MCF) and Santa Barbara Amorphous (SBA-15) silica supports using adsorption or covalently with glutaraldehyde or divinyl sulfone linkers. The best catalyst, AcmB on MCF linked covalently with glutaraldehyde, retained the specific activity of the homogenous enzyme while exhibiting a substantial increase of the operational stability. The immobilized enzyme was used continuously in the fed-batch reactor for 27 days, catalyzing 1,2-dehydrogenation of androst-4-en-3-one to androst-1,4-dien-3-one with a final yield of 29.9 mM (8.56 g/L) and 99% conversion. The possibility of reuse of the immobilized catalyst was also demonstrated and resulted in a doubling of the product amount compared to that in the reference homogenous reactor. Finally, it was shown that molecular oxygen from the air can efficiently be used as an electron acceptor either reoxidizing directly the enzyme or the reduced 2,4-dichlorophenolindophenol (DCPIPH₂). Full article

As an important hormone drug intermediate, androst-1,4-diene-3,17-dione can be bio-converted from phytosterols. However, separation and purification in the downstream process are very difficult due to the similarity in structure and physiological characteristics between ADD and androstenedione (AD). This phenomenon was correlated to the insufficient enzyme activity of 3-ketosteroid-Δ¹-dehydrogenase (KSDD), which specifically catalyzes the C_1,2 dehydrogenation of AD. In order to obtain a highly purified ADD from phytosterols, the dehydrogenation effect of different kinds of KSDDs and the transcription effect of four promoter sequences on ksdd were analyzed in Mycobacterium sp. ZFZ (ZFZ), the cell host that transform phytosterols to AD in the oil-aqueous system. A tandem KSDD expression cassette containing strain ZFZ-2111 yielded 2.06 ± 0.09 g L⁻¹ ADD, with a molar ratio of ADD/AD at 41.47:1.00 in 120 h. In waste cooking oil-aqueous media, the proportion of ADD in the fermentation by ZFZ-2111 was 92%. The present study provides a reliable theoretical basis for the step-by-step transformation of phytosterols to ADD. Full article

Prednisone and prednisolone are steroids widely used as anti-inflammatory drugs. Development of the pharmaceutical industry is currently aimed at introducing biotechnological processes and replacing multiple-stage chemical syntheses. In this work we evaluated the ability of bacteria belonging to the Rhodococcus genus to biotransform substrates, such as cortisone and hydrocortisone, to obtain prednisone and prednisolone, respectively. These products are of great interest from a pharmaceutical point of view as they have higher anti-inflammatory activity than the starting substrates. After an initial lab-scale screening of 13 Rhodococcus strains, to select the highest producers of prednisone and prednisolone, we reported the 200 ml-batch scale-up to test the process efficiency and productivity of the most promising Rhodococcus strains. R. ruber, R. globerulus and R. coprophilus gave the Δ1-dehydrogenation products of cortisone and hydrocortisone (prednisone and prednisolone) in variable amounts. In these biotransformations, the formation of products with the reduced carbonyl group in position C₂₀ of the lateral chain of the steroid nucleus was also observed (i.e., 20β-hydroxy-prednisone and 20β-hydroxy-prednisolone). The yields, the absence of collateral products, and in some cases the absence of starting products allow us to say that cortisone and hydrocortisone are partly degraded. Full article