Co-production of 11α-hydroxyprogesterone and ethanol using recombinant yeast expressing fungal steroid hydroxylases

A highly efficient mixed strain fermentation strategy to produce 11α-Hydroxyandrost-4-ene-3,17-dione from phytosterols

11α-Hydroxyandrost-4-ene-3,17-dione (11α-OH AD) is an essential steroid hormone drug intermediate that exhibits low biotransformation efficiency. In this study, a mixed-strain fermentation strategy was established for the efficient production of 11α-OH AD from phytosterols (PS). Initially, strains were screened for efficient transformation of AD to produce 11α-OH AD. Subsequently, a dual-strain mixed-culture fermentation technique was established, with Mycolicibacterium neoaurum CICC 21097 ΔksdD (MNR) showing highly effective results. Ultimately, a one-step conversion process for the production of 11α-OH AD was achieved at a molar yield of 76.5 % under optimal conditions using PS as a substrate, the highest reported yield to date. Additionally, studies revealed synergistic metabolic interactions between MNR and Aspergillus ochraceus in the mixed-culture system. These findings provide valuable insights for the industrial production of high-value products using mixed-strain fermentation.

Cofactor-dependence alteration of 7β-hydroxysteroid dehydrogenase: Enhancing one-pot synthesis efficiency of chenodeoxycholic acid to ursodeoxycholic acid through cofactor self-recycling

NAD+-dependent 7α-hydroxysteroid dehydrogenase (7α-HSDH) and NADPH-dependent 7β-hydroxysteroid dehydrogenase (7β-HSDH) are involved in the biosynthesis of chenodeoxycholic acid (CDCA) to ursodeoxycholic acid (UDCA). To realize the one-pot synthesis of CDCA to UDCA through NAD+-NADH cycling, we aimed to improve the binding ability of Hyphomicrobium sp. 7β-HSDH to NADH. The 7β-HSDH structure was modeled and some potential residues to improve NADH affinity near conserved cofactor binding regions were screened, including Ala22, Gln23, Asn24, Asp44, Leu45, and Asn46. The dominant mutant A22T/Q23E/L45A/N46E significantly enhanced the binding affinity for NADH, resulting in a 44.9-fold increase in its kcat/Km value. It increased enzymatic activity by 65.2-fold and catalyzed the synthesis of UDCA at a yield of 77.6 % with 5 g/L 7K-LCA and 12.5 mM NADH. Molecular dynamics simulations indicated increased interactions of mutated 7β-HSDH and the ligand NADH by their spatially reduced binding distance and reaction energy. The modified cofactor-dependence of 7β-HSDH realized efficient one-pot synthesis of CDCA to UDCA through strengthening cofactor-recycling and reducing the use of cofactor, achieving 90.1 % UDCA yield and 54.1 g/L/d spatiotemporal yield when coupled with 7α-HSDH with only 0.5 mM NAD+ as coenzyme. This work also supplies a universal cofactor-dependence engineering technique for homologous HSDH enzymes.

Novel cytochrome P450s for various hydroxylation of steroids from filamentous fungi

Hydroxylated steroids are value-added products with diverse biological activities mediated by cytochrome P450 enzymes, however, few has been thoroughly characterized in fungi. This study introduces a rapid identification strategy for filamentous fungi P450 enzymes through transcriptome and bioinformatics analysis. Five novel enzymes (CYP68J5, CYP68L10, CYP68J3, CYP68N1 and CYP68N3) were identified and characterized in Saccharomyces cerevisiae or Aspergillus oryzae. Molecular docking and dynamics simulations were employed to elucidate hydroxylation preferences of CYP68J5 (11α, 7α bihydroxylase) and CYP68N1 (11α hydroxylase). Additionally, redox partners (cytochrome P450 reductase and cytochrome b5) and ABC transporter were co-expressed with CYP68N1 to enhance 11α-OH-androstenedione (11α-OH-4AD) production. The engineered cell factory, co-expressing CPR1 and CYP68N1, achieved a significant increase of 11α-OH-4AD production, reaching 0.845 g·L-1, which increased by 14 times compared to the original strain. This study provides a comprehensive approach for identifying and implementing novel cytochrome P450 enzymes, paving the way for sustainable production of steroidal products.

Biotransformation of Androstenedione by Filamentous Fungi Isolated from Cultural Heritage Sites in the State Tretyakov Gallery

Simple Summary

Microorganisms are able to grow on substrates of the most diverse nature. One of the most practical habitats, in terms of cultural heritage conservation, is fine art objects such as tempera or oil paintings on canvas. Since tempera paints are produced on the basis of egg yolk, which is one of the richest sources of cholesterol in nature (up to 2% of dry weight), and in the process of aging of tempera materials, changes in cholesterol do not affect the core structure of the steroid nucleus, the group of fungi that we have isolated are tempera painting destructors is seen as a promising object for screening for their possible steroid-transforming activities. In this regard, the purpose of our work was to determine the ability to transform pharmaceutically significant steroids with dominant fungi-destructors of tempera paintings, previously isolated in the State Tretyakov Gallery. Consequently, we have demonstrated for the first time that fungi-destructors of tempera paintings have steroid-transforming activity and are promising microorganisms for screening for biotechnologically significant transformations of steroids with further industrial use.

Abstract

The transformation of steroids by microorganisms is widely used in medical biotechnology. A huge group of filamentous fungi is one of the most promising taxa for screening new biocatalytic reactions in order to obtain pharmaceutically significant steroids. In this work, we screened 10 filamentous fungi-destructors of egg tempera for the ability to biotransform androst-4-en-3,17-dione (AD) during cultivation in a liquid nutrient medium or in a buffer solution. These taxonomically unrelated strains, belonging to the classes Eurotiomycetes, Dothideomycetes and Sordariomycetes, are dominant representatives of the microbiome from halls where works of tempera painting are stored in the State Tretyakov Gallery (STG, Moscow, Russia). Since the binder of tempera paints, egg yolk, contains about 2% cholesterol, these degrading fungi appear to be a promising group for screening for steroid converting activity. It turned out that all the studied fungi-destructors are able to transform AD. Some strains showed transformation efficiency close to the industrial strain Curvularia lunata RNCIM F-981. In total, 33 steroids formed during the transformation of AD were characterized, for 19 of them the structure was established by gas chromatography/mass spectrometry analysis. In this work, we have shown for the first time that fungi-destructors of tempera paintings can efficiently transform steroids.

Engineering of a fungal steroid 11α-hydroxylase and construction of recombinant yeast for improved production of 11α-hydroxyprogesterone

Cytochrome P450 enzyme CYP68J5 from filamentous fungus Aspergillus ochraceus is industrially used for selective C11α-hydroxylation of canrenone and progesterone. To improve its selectivity of C11α-hydroxylation for relevant steroid substrates, a sequence-based targeted mutagenesis combined with saturation mutagenesis was conducted to search for variants with improved hydroxylation reaction specificity toward progesterone and D-ethylgonendione. Recombinant yeast expressing triple mutant V64F/E65G/N66T showed significantly increased C11α-hydroxylation selectivity (85 % VS WT 69.7 %). Saturation mutagenesis of V64, E65 and N66 resulted in the identification of single mutant V64K with greatly enhanced 11α-hydroxylation specificity toward progesterone (90.6 % VS WT 69.7 %). Furthermore, mutant N66D showed significant enhanced selectivity of C11α-hydroxylation toward D-ethylgonendione (70.8 % VS WT 58 %). Evaluation of recombinant yeast over-expressing V64K for progesterone transformation in 50 mL scale resulted in product 11α-OH progesterone concentrations of 432.5 mg/L, a 30.2 % increase compared with the CYP68J5 control. Our results also reveal that V64, E65 and N66 are key residues of CYP68J5 influencing its selectivity of C11α-hydroxylation, thus offering opportunities for further engineering of CYP68J5 for expanded industrial applications.

Production of 11α-hydroxysteroids from sterols in a single fermentation step by Mycolicibacterium smegmatis

11α-hydroxylated steroid synthons are one of the most important commercially pharmaceutical intermediates used for the production of contraceptive drugs and glucocorticoids. These compounds are currently produced by biotransformation using fungal strains in two sequential fermentation steps. In this work, we have developed by a rational design new recombinant bacteria able to produce 11α-hydroxylated synthons in a single fermentation step using cholesterol (CHO) or phytosterols (PHYTO) as feedstock. We have designed a synthetic operon expressing the 11α-hydroxylating enzymes from the fungus Rhizopus oryzae that was cloned into engineered mutant strains of Mycolicibacterium smegmatis that were previously created to produce 4-androstene-3,17-dione (AD), 1,4-androstadiene-3,17-dione (ADD) from sterols. The introduction of the fungal synthetic operon in these modified bacterial chassis has allowed producing for the first time 11αOH-AD and 11αOH-ADD with high yields directly from sterols in a single fermentation step. Remarkably, the enzymes of sterol catabolic pathway from M. smegmatis recognized the 11α-hydroxylated intermediates as alternative substrates and were able to efficiently funnel sterols to the desired hydroxylated end-products.

Engineering the Steroid Hydroxylating System from Cochliobolus lunatus in Mycolicibacterium smegmatis

14α-hydroxylated steroids are starting materials for the synthesis of contraceptive and anti-inflammatory compounds in the steroid industry. A synthetic bacterial operon containing the cytochrome P450 CYP103168 and the reductase CPR64795 of the fungus Cochlioboluslunatus able to hydroxylate steroids has been engineered into a shuttle plasmid named pMVFAN. This plasmid was used to transform two mutants of Mycolicibacterium smegmatis named MS6039-5941 and MS6039 that accumulate 4-androstene-3,17-dione (AD), and 1,4-androstadiene-3,17-dione (ADD), respectively. The recombinant mutants MS6039-5941 (pMVFAN) and MS6039 (pMVFAN) were able to efficiently express the hydroxylating CYP system of C.lunatus and produced in high yields 14αOH-AD and 14αOH-ADD, respectively, directly from cholesterol and phytosterols in a single fermentation step. These results open a new avenue for producing at industrial scale these and other hydroxylated steroidal synthons by transforming with this synthetic operon other Mycolicibacterium strains currently used for the commercial production of steroidal synthons from phytosterols as feedstock.

Improved 11α-hydroxycanrenone production by modification of cytochrome P450 monooxygenase gene in Aspergillus ochraceus

Eplerenone is a drug that protects the cardiovascular system. 11α-Hydroxycanrenone is a key intermediate in eplerenone synthesis. We found that although the cytochrome P450 (CYP) enzyme system in Aspergillus ochraceus strain MF018 could catalyse the conversion of canrenone to 11α-hydroxycanrenone, its biocatalytic efficiency is low. To improve the efficiency of 11α-hydroxycanrenone production, the CYP monooxygenase-coding gene of MF018 was predicted and cloned based on whole-genome sequencing results. A recombinant A. ochraceus strain MF010 with the high expression of CYP monooxygenase was then obtained through homologous recombination. The biocatalytic rate of this recombinant strain reached 93 % at 60 h without the addition of organic solvents or surfactants and was 17-18 % higher than that of the MF018 strain. Moreover, the biocatalytic time of the MF010 strain was reduced by more than 30 h compared with that of the MF018 strain. These results show that the recombinant A. ochraceus strain MF010 can overcome the limitation of substrate biocatalytic efficiency and thus holds a high poten tial for application in the industrial production of eplerenone.

Yeast as a promising heterologous host for steroid bioproduction

With the rapid development of synthetic biology and metabolic engineering technologies, yeast has been generally considered as promising hosts for the bioproduction of secondary metabolites. Sterols are essential components of cell membrane, and are the precursors for the biosynthesis of steroid hormones, signaling molecules, and defense molecules in the higher eukaryotes, which are of pharmaceutical and agricultural significance. In this mini-review, we summarize the recent engineering efforts of using yeast to synthesize various steroids, and discuss the structural diversity that the current steroid-producing yeast can achieve, the challenge and the potential of using yeast as the bioproduction platform of various steroids from higher eukaryotes.

Biotransformation of progesterone by Aspergillus nidulans VKPM F-1069 (wild type)

Biotechnological transformation of steroids using enzyme systems of microorganisms is often the only possible method to modify the molecule in the industrial production of steroid drugs. Filamentous fungus Aspergillus nidulans has been little studied as a steroid-transforming microorganism. We studied the ability of the A. nidulans VKPM F-1069 strain to transform progesterone (PG) for the first time. This strain converts PG into 3 main products: 11α-hydroxy-PG, 11α-acetoxy-PG and 6β,11α-dihydroxy-PG. It has been established that in the first stage, the hydroxylation of PG occurs into C11α position, then the formed 11α-hydroxy-PG is modified into 11α-acetoxy-PG and 6β,11α-dihydroxy-PG. It was found that changes in the composition of the growth medium, aeration and the duration of the mycelium cultivation do not affect the qualitative composition of PG transformation products, but their ratios have changed. Under conditions of limited aeration, the direction of secondary modification of 11α-hydroxy-PG is shifted towards the formation of 11α-acetoxy-PG.

Biosynthesis of clinically used antibiotic fusidic acid and identification of two short-chain dehydrogenase/reductases with converse stereoselectivity

Fusidic acid is the only fusidane-type antibiotic that has been clinically used. However, biosynthesis of this important molecule in fungi is poorly understood. We have recently elucidated the biosynthesis of fusidane-type antibiotic helvolic acid, which provides us with clues to identify a possible gene cluster for fusidic acid (fus cluster). This gene cluster consists of eight genes, among which six are conserved in the helvolic acid gene cluster except fusC1 and fusB1. Introduction of the two genes into the Aspergillus oryzae NSAR1 expressing the conserved six genes led to the production of fusidic acid. A stepwise introduction of fusC1 and fusB1 revealed that the two genes worked independently without a strict reaction order. Notably, we identified two short-chain dehydrogenase/reductase genes fusC1 and fusC2 in the fus cluster, which showed converse stereoselectivity in 3-ketoreduction. This is the first report on the biosynthesis and heterologous expression of fusidic acid.

Electricity-driven 7α-hydroxylation of a steroid catalyzed by a cytochrome P450 monooxygenase in engineered yeast

Schematic diagram of the cytochrome P450 monooxygenase-catalyzed BES.