Enhanced biotransformation of dehydroepiandrosterone to 3β,7α,15α-trihydroxy-5-androsten-17-one with Gibberella intermedia CA3-1 by natural oils addition

New Insights into the Modification of the Non-Core Metabolic Pathway of Steroids in Mycolicibacterium and the Application of Fermentation Biotechnology in C-19 Steroid Production

Androsta-4-ene-3,17-dione (AD), androsta-1,4-diene-3,17-dione (ADD), and 9α-hydroxy-4-androstene-3,17-dione (9-OHAD), which belong to C-19 steroids, are critical steroid-based drug intermediates. The biotransformation of phytosterols into C-19 steroids by Mycolicibacterium cell factories is the core step in the synthesis of steroid-based drugs. The production performance of engineered mycolicibacterial strains has been effectively enhanced by sterol core metabolic modification. In recent years, research on the non-core metabolic pathway of steroids (NCMS) in mycolicibacterial strains has made significant progress. This review discusses the molecular mechanisms and metabolic modifications of NCMS for accelerating sterol uptake, regulating coenzyme I balance, promoting propionyl-CoA metabolism, reducing reactive oxygen species, and regulating energy metabolism. In addition, the recent applications of biotechnology in steroid intermediate production are summarized and compared, and the future development trend of NCMS research is discussed. This review provides powerful theoretical support for metabolic regulation in the biotransformation of phytosterols.

Correlation Relationship between Phase Inversion of Pickering Emulsions and Biocatalytic Activity of Microbial Transformation of Phytosterols

Microbial transformation of hydrophobic phytosterols into the pharmaceutical steroid precursors AD (androst-4-ene-3, 17-dione) and ADD (androst-4-diene-3, 17-dione) in a water–plant oil two-phase system by Mycolicibacterium neoaurum is a paradigm of interfacial biocatalysis in Pickering emulsions stabilized by bacterial cells. In the present work, phase inversion of Pickering emulsions—i.e., Pickering emulsions turning from water-in-oil (W/O) emulsions into oil-in-water (O/W) ones—was observed during microbial transformation in the presence of high concentrations of crystal phytosterols. It was found that there is a correlation relationship between the phase behaviors of Pickering emulsions and the biocatalytic activity of utilizing M. neoaurum as a whole-cell catalyst. Efficient microbial transformation under the high crystal phytosterol loadings was achieved due to the formation of O/W emulsions where interfacial biocatalysis took place. Under the optimal conditions (volume ratio of soybean oil to water: 15:35 mL, phytosterols concentration in the soybean oil: 80 g/L, glucose as co-substrate in the aqueous culture medium: 10 g/L), the concentrations of AD and ADD reached 4.8 g/L based on the whole broth (16 g/L based on the oil phase) after microbial transformation for 9 days.

Hydroxylation of pregnenolone and dehydroepiandrosterone by zygomycete Backusella lamprospora VKM F-944: selective production of 7α-OH-DHEA

In this paper, we studied the transformation of two 3β-hydroxy-5-ene-steroids-pregnenolone and dehydroepiandrosterone (DHEA) by Backusella lamprospora VKM F- 944. The soil-dwelling zygomycete wild-type strain has been earlier selected during the screening and previously unexplored for this purpose. The fungus fully converted pregnenolone to form a mixture of axial 7α-hydroxy-pregnenolone and 7α,11α-dihydroxy-pregnenolone, while no metabolites with β-orientation of the hydroxyl group were detected. The pathway to 7α,11α-diOH-pregnenolone seems to include 7α-hydroxylation of 11α-hydroxylated derivative. The only product from DHEA was identified as 7α-hydroxy-DHEA. The structures of steroid metabolites were confirmed by HPLC, mass-spectrometry (MS), and ¹H and ¹³C NMR analyses. Under the optimized conditions, the yield of 7α-OH-DHEA reached 94% (w/w) or over 14 g/L in absolute terms, even at high concentration of the substrate (DHEA) (15 g/L). To our knowledge, it is the highest yield of the value-added 7α-OH-DHEA reported so far. The results contribute to the knowledge of the diversity of the wild-type fungal strains capable of effective steroid hydroxylation. They could be applied for the production of allylic steroid 7α-alcohols that are widely used in medicine. KEY POINTS: • Zygomycete Backusella lamprospora actively hydroxylates 3β-hydroxy-5-en-steroids. • Axial 7α-hydroxylation is the preferable reaction by the strain towards pregnenolone and DHEA. • The strain selectively produces 7α-OH-DHEA even at high substrate concentrations (up to 15 g/L).

iTRAQ-based quantitative proteomic analysis of Colletotrichum lini reveals ethanol induced mechanism for enhancing dihydroxylation efficiency of DHEA

Colletotrichum lini is used as an industrial stain for the dihydroxylation of steroid compound dehydroepiandrosterone (DHEA) to biosynthesize 3β,7α,15α-trihydroxy-5-androstene-17-one (7α,15α-diOH-DHEA), a key intermediate of the most popular oral contraceptive "Yasmin". This work aimed to enhance 7α,15α-diOH-DHEA production in C. lini CGMCC 6051 through ethanol induction. With 0.6% (v/v) ethanol induction and 10 g/L DHEA concentration, the 7α,15α-diOH-DHEA molar yield reached 58.8%, which was increased by 67.5% than that of the control. iTRAQ-based quantitative proteomic analysis was applied to explore the probable molecular mechanism of C. lini response to ethanol induction. A total of 50 differential expressed proteins was affected by ethanol induction, and could be related to multiple metabolic pathways. Most of differently expressed proteins were functionally mapped into pathways of transport, steroids metabolism, or redox reaction. Other proteins for energy, transcription and translation, and carbohydrate metabolism might have important roles in the cellular response to ethanol induction. In addition, the levels of cytochrome P450 and NAD(P)H-cytochrome P450 reductase were remarkably higher under ethanol induction, and their functions on DHEA dihydroxylation were first proposed in C. lini. Our results provide critical clues in revealing the dihydroxylation mechanism and are important for efficient microbiological hydroxylation of steroidal compounds in the future. BIOLOGICAL SIGNIFICANCE: iTRAQ strategy was first used to compare the proteomes of ethanol induction during the dihydroxylation reaction by Colletotrichum lini CGMCC 6051. The changes in protein provided a comprehensive overview of DHEA dihydroxylation in C. lini, including the proteins for steroids metabolism, redox reaction, transport, transcription and translation, energy and carbohydrate metabolism. Cytochrome P450, NADPH-cytochrome P450 reductase, and NADH-cytochrome b5 reductase were highlighted due to their outstanding contribution to DHEA dihydroxylation. The results help us understand the molecular mechanism underlying ethanol induction in C. lini and would guide strain engineering to further improve dihydroxylation efficiency.

Biotransformation of DHEA into 7α,15α-diOH-DHEA

3β,7α,15α-Trihydroxy-5-androsten-17-one (7α,15α-diOH-DHEA) is a key intermediate of the novel oral contraceptive "Yasmin" (widely used in birth control pills and postmenopausal hormone replacement therapy pills; the active ingredient is drospirenone). It can be synthesized from dehydroepiandrosterone (DHEA) by microbial dihydroxylation at the C7 and C15 positions. Here we describe the method of bioconversion from DHEA into 7α,15α-diOH-DHEA by Colletotrichum lini. Using 6 g/L DHEA as a substrate, the DHEA conversion and the 7α,15α-diOH-DHEA molar yield were 72.6% and 51.2%, respectively.

Genome shuffling of Colletotrichum lini for improving 3β,7α,15α-trihydroxy-5-androsten-17-one production from dehydroepiandrosterone

3β,7α,15α-Trihydroxy-5-androsten-17-one (7α,15α-diOH-DHEA) is a key intermediate of the novel oral contraceptive Yasmin. It can be catalyzed from dehydroepiandrosterone (DHEA) through Colletotrichum lini. Improvement of 7α,15α-diOH-DHEA production was performed through recursive protoplast fusion of C. lini ST in a genome shuffling format. 7α,15α-diOH-DHEA yield of the best performing recombinant C. lini ST-F307 reached 6.08 g/L from 10 g/L DHEA, and this was 94.9% higher than that of the initial C. lini ST strain. Through optimized conditions, the 7α,15α-diOH-DHEA yield was increased to 9.32 g/L from 12 g/L DHEA, with 1.5% ethanol as cosolvent. This is the highest reported substrate concentration and 7α,15α-diOH-DHEA production with one-step substrate addition. Moreover, C. lini ST-F307 showed high P450 enzyme activity and gene transcript levels of several cytochrome P450s, and this might contribute to the enhancement of 7α,15α-diOH-DHEA production. Genome shuffling was an efficient approach to breed high-yield strains.

Improvement of NADPH-dependent P450-mediated biotransformation of 7α,15α-diOH-DHEA from DHEA by a dual cosubstrate-coupled system

Hydroxylation of DHEA to 7α,15α-diOH-DHEA was catalyzed by NADPH-dependent cytochrome P450 monooxygenase from Colletotrichum lini. By adding coenzyme precursor nicotinic acid, the NADPH/NADP ratio was significantly increased, and the 7α,15α-diOH-DHEA molar conversion was enhanced from 37.37% to 50.85%. To improve the availability of intracellular NADPH, a dual cosubstrate-coupled system consisting of nicotinic acid and glucose was investigated in C. lini. Using 20mM nicotinic acid and 15g/L glucose as cosubstrate for NADPH regeneration, the 7α,15α-diOH-DHEA molar conversion was dramatically increased by 74.58%. The conversion course was simultaneously shortened by 30h. Moreover, a fed-batch transformation model was established to diminish DHEA toxicity to C. lini and further increase DHEA concentration. The maximum concentration of DHEA was elevated to 15g/L using a three-batch transformation in a coenzyme regeneration system, and 7α,15α-diOH-DHEA production of 11.21g/L could be achieved after 60h of biotransformation. These results demonstrated that this strategy was promising for steroids hydroxylation.