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Weckerle T, Ewald H, Guth P, Knorr K, Philipp B, Holert J. Biogas digestate as a sustainable phytosterol source for biotechnological cascade valorization. Microb Biotechnol 2022; 16:337-349. [PMID: 36415958 PMCID: PMC9871531 DOI: 10.1111/1751-7915.14174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/26/2022] [Accepted: 10/30/2022] [Indexed: 11/24/2022] Open
Abstract
Every year, several million tonnes of anaerobic digestate are produced worldwide as a by-product of the biogas industry, most of which is applied as agricultural fertilizer. However, in the context of a circular bioeconomy, more sustainable uses of residual digestate biomass would be desirable. This study investigates the fate of the sterol lipids β-sitosterol and cholesterol from the feedstocks to the final digestates of three agricultural and one biowaste biogas plants to assess if sterols are degraded during anaerobic digestion or if they remain in the digestate, which could provide a novel opportunity for digestate cascade valorization. Gas chromatographic analyses showed that feedstock sterols were not degraded during anaerobic digestion, resulting in their accumulation in the digestates to up to 0.15% of the dry weight. The highest concentrations of around 1440 mg β-sitosterol and 185 mg cholesterol per kg dry weight were found in liquid digestate fractions, suggesting partial sterol solubilization. Methanogenic batch cultures spiked with β-sitosterol, cholesterol, testosterone and β-oestradiol confirmed that steroids persist during anaerobic digestion. Mycobacterium neoaurum was able to transform digestate sterols quantitatively into androstadienedione, a platform chemical for steroid hormones, without prior sterol extraction or purification. These results suggest that digestate from agricultural and municipal biowaste is an untapped resource for natural sterols for biotechnological applications, providing a new strategy for digestate cascade valorization beyond land application.
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Affiliation(s)
- Tim Weckerle
- Institute for Molecular Microbiology and BiotechnologyMicrobial Biotechnology & Ecology Group, University of MünsterMünsterGermany
| | - Helen Ewald
- Institute for Molecular Microbiology and BiotechnologyMicrobial Biotechnology & Ecology Group, University of MünsterMünsterGermany
| | - Patrick Guth
- Institute of Landscape Ecology, Ecohydrology & Biogeochemistry GroupUniversity of MünsterMünsterGermany
| | - Klaus‐Holger Knorr
- Institute of Landscape Ecology, Ecohydrology & Biogeochemistry GroupUniversity of MünsterMünsterGermany
| | - Bodo Philipp
- Institute for Molecular Microbiology and BiotechnologyMicrobial Biotechnology & Ecology Group, University of MünsterMünsterGermany
| | - Johannes Holert
- Institute for Molecular Microbiology and BiotechnologyMicrobial Biotechnology & Ecology Group, University of MünsterMünsterGermany
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Feller FM, Eilebrecht S, Nedielkov R, Yücel O, Alvincz J, Salinas G, Ludwig KC, Möller H, Philipp B. Investigations on the Degradation of the Bile Salt Cholate via the 9,10- Seco-Pathway Reveals the Formation of a Novel Recalcitrant Steroid Compound by a Side Reaction in Sphingobium sp. Strain Chol11. Microorganisms 2021; 9:microorganisms9102146. [PMID: 34683472 PMCID: PMC8540908 DOI: 10.3390/microorganisms9102146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/07/2021] [Accepted: 10/11/2021] [Indexed: 01/30/2023] Open
Abstract
Bile salts such as cholate are steroid compounds from the digestive tracts of vertebrates, which enter the environment upon excretion, e.g., in manure. Environmental bacteria degrade bile salts aerobically via two pathway variants involving intermediates with Δ1,4- or Δ4,6-3-keto-structures of the steroid skeleton. Recent studies indicated that degradation of bile salts via Δ4,6-3-keto intermediates in Sphingobium sp. strain Chol11 proceeds via 9,10-seco cleavage of the steroid skeleton. For further elucidation, the presumptive product of this cleavage, 3,12β-dihydroxy-9,10-seco-androsta-1,3,5(10),6-tetraene-9,17-dione (DHSATD), was provided to strain Chol11 in a co-culture approach with Pseudomonas stutzeri Chol1 and as purified substrate. Strain Chol11 converted DHSATD to the so far unknown compound 4-methyl-3-deoxy-1,9,12-trihydroxyestra-1,3,5(10)7-tetraene-6,17-dione (MDTETD), presumably in a side reaction involving an unusual ring closure. MDTETD was neither degraded by strains Chol1 and Chol11 nor in enrichment cultures. Functional transcriptome profiling of zebrafish embryos after exposure to MDTETD identified a significant overrepresentation of genes linked to hormone responses. In both pathway variants, steroid degradation intermediates transiently accumulate in supernatants of laboratory cultures. Soil slurry experiments indicated that bacteria using both pathway variants were active and also released their respective intermediates into the environment. This instance could enable the formation of recalcitrant steroid metabolites by interspecies cross-feeding in agricultural soils.
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Affiliation(s)
- Franziska Maria Feller
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (O.Y.); (K.C.L.)
| | - Sebastian Eilebrecht
- Fraunhofer Attract Eco’n’OMICs, Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Auf dem Aberg 1, 57392 Schmallenberg, Germany; (S.E.); (J.A.)
| | - Ruslan Nedielkov
- Institute for Chemistry, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany; (R.N.); (H.M.)
| | - Onur Yücel
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (O.Y.); (K.C.L.)
| | - Julia Alvincz
- Fraunhofer Attract Eco’n’OMICs, Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Auf dem Aberg 1, 57392 Schmallenberg, Germany; (S.E.); (J.A.)
| | - Gabriela Salinas
- NGS-Services for Integrative Genomics, Institute for Human Genetics, University of Göttingen, 37077 Göttingen, Germany;
| | - Kevin Christopher Ludwig
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (O.Y.); (K.C.L.)
| | - Heiko Möller
- Institute for Chemistry, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany; (R.N.); (H.M.)
| | - Bodo Philipp
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (O.Y.); (K.C.L.)
- Department for Environmental Microbiology, Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Auf dem Aberg 1, 57392 Schmallenberg, Germany
- Correspondence: ; Tel.: +49-251-8339827; Fax: +49-251-8338388
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Feller FM, Holert J, Yücel O, Philipp B. Degradation of Bile Acids by Soil and Water Bacteria. Microorganisms 2021; 9:1759. [PMID: 34442838 PMCID: PMC8399759 DOI: 10.3390/microorganisms9081759] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 07/22/2021] [Accepted: 08/12/2021] [Indexed: 02/07/2023] Open
Abstract
Bile acids are surface-active steroid compounds with a C5 carboxylic side chain at the steroid nucleus. They are produced by vertebrates, mainly functioning as emulsifiers for lipophilic nutrients, as signaling compounds, and as an antimicrobial barrier in the duodenum. Upon excretion into soil and water, bile acids serve as carbon- and energy-rich growth substrates for diverse heterotrophic bacteria. Metabolic pathways for the degradation of bile acids are predominantly studied in individual strains of the genera Pseudomonas, Comamonas, Sphingobium, Azoarcus, and Rhodococcus. Bile acid degradation is initiated by oxidative reactions of the steroid skeleton at ring A and degradation of the carboxylic side chain before the steroid nucleus is broken down into central metabolic intermediates for biomass and energy production. This review summarizes the current biochemical and genetic knowledge on aerobic and anaerobic degradation of bile acids by soil and water bacteria. In addition, ecological and applied aspects are addressed, including resistance mechanisms against the toxic effects of bile acids.
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Affiliation(s)
- Franziska Maria Feller
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (J.H.); (O.Y.)
| | - Johannes Holert
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (J.H.); (O.Y.)
| | - Onur Yücel
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (J.H.); (O.Y.)
| | - Bodo Philipp
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (J.H.); (O.Y.)
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Auf dem Aberg 1, 57392 Schmallenberg, Germany
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