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Li S, Fan S, Peng X, Zheng D, Li D. Using ferrous-oxidizing bacteria to enhance the performance of a pH neutral all-iron flow battery. iScience 2024; 27:108595. [PMID: 38174320 PMCID: PMC10762366 DOI: 10.1016/j.isci.2023.108595] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Revised: 11/14/2023] [Accepted: 11/28/2023] [Indexed: 01/05/2024] Open
Abstract
Among various redox flow batteries (RFBs), the all-iron RFBs have greater application potential due to high accessibility of electrolytes. However, the potential of microaerobic ferrous-oxidizing bacteria (FeOB) to improve the performance of RFB has been neglected. Here, several experiments were conducted using Fe2+-diethylenetriaminepentaacetic acid (DTPA)/Na3[Fe(CN)6] as a redox couple for investigating the enhanced performance by FeOB in this RFB. Results showed that the maximum current density of experimental reactors could achieve 22.56 A/m2 at 0.1 M, whereas power density could still maintain 3.42 W/m2(16.96 A/m2 and 1.58 W/m2 for control group); meantime, the polarization impedance of anode increased slower and Fe2+-DTPA oxidation peak emerged maximum 494 mV negative shift. With increased electrolyte concentration in chronopotentiometry experiments, the experimental reactor achieved higher discharging specific capacity at 0.3 M, 10 mA/cm2. Microbial composition analysis showed maximum 75% is Brucella, indicating Brucella has ferrous-oxidizing electroactivity.
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Affiliation(s)
- Sitao Li
- Key Laboratory of Environmental and Applied Microbiology, Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Science, Chengdu 610041, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Sen Fan
- Key Laboratory of Environmental and Applied Microbiology, Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Science, Chengdu 610041, China
- Collage of Life Sciences, Sichuan University, Chengdu 610041, China
| | - Xinyuan Peng
- Key Laboratory of Environmental and Applied Microbiology, Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Science, Chengdu 610041, China
- Collage of Life Sciences, Sichuan University, Chengdu 610041, China
| | - Decong Zheng
- Key Laboratory of Environmental and Applied Microbiology, Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Science, Chengdu 610041, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Daping Li
- Key Laboratory of Environmental and Applied Microbiology, Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Science, Chengdu 610041, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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2
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Werner F, Schwardmann LS, Siebert D, Rückert-Reed C, Kalinowski J, Wirth MT, Hofer K, Takors R, Wendisch VF, Blombach B. Metabolic engineering of Corynebacterium glutamicum for fatty alcohol production from glucose and wheat straw hydrolysate. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:116. [PMID: 37464396 DOI: 10.1186/s13068-023-02367-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 07/07/2023] [Indexed: 07/20/2023]
Abstract
BACKGROUND Fatty acid-derived products such as fatty alcohols (FAL) find growing application in cosmetic products, lubricants, or biofuels. So far, FAL are primarily produced petrochemically or through chemical conversion of bio-based feedstock. Besides the well-known negative environmental impact of using fossil resources, utilization of bio-based first-generation feedstock such as palm oil is known to contribute to the loss of habitat and biodiversity. Thus, the microbial production of industrially relevant chemicals such as FAL from second-generation feedstock is desirable. RESULTS To engineer Corynebacterium glutamicum for FAL production, we deregulated fatty acid biosynthesis by deleting the transcriptional regulator gene fasR, overexpressing a fatty acyl-CoA reductase (FAR) gene of Marinobacter hydrocarbonoclasticus VT8 and attenuating the native thioesterase expression by exchange of the ATG to a weaker TTG start codon. C. glutamicum ∆fasR cg2692TTG (pEKEx2-maqu2220) produced in shaking flasks 0.54 ± 0.02 gFAL L-1 from 20 g glucose L-1 with a product yield of 0.054 ± 0.001 Cmol Cmol-1. To enable xylose utilization, we integrated xylA encoding the xylose isomerase from Xanthomonas campestris and xylB encoding the native xylulose kinase into the locus of actA. This approach enabled growth on xylose. However, adaptive laboratory evolution (ALE) was required to improve the growth rate threefold to 0.11 ± 0.00 h-1. The genome of the evolved strain C. glutamicum gX was re-sequenced, and the evolved genetic module was introduced into C. glutamicum ∆fasR cg2692TTG (pEKEx2-maqu2220) which allowed efficient growth and FAL production on wheat straw hydrolysate. FAL biosynthesis was further optimized by overexpression of the pntAB genes encoding the membrane-bound transhydrogenase of E. coli. The best-performing strain C. glutamicum ∆fasR cg2692TTG CgLP12::(Ptac-pntAB-TrrnB) gX (pEKEx2-maqu2220) produced 2.45 ± 0.09 gFAL L-1 with a product yield of 0.054 ± 0.005 Cmol Cmol-1 and a volumetric productivity of 0.109 ± 0.005 gFAL L-1 h-1 in a pulsed fed-batch cultivation using wheat straw hydrolysate. CONCLUSION The combination of targeted metabolic engineering and ALE enabled efficient FAL production in C. glutamicum from wheat straw hydrolysate for the first time. Therefore, this study provides useful metabolic engineering principles to tailor this bacterium for other products from this second-generation feedstock.
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Affiliation(s)
- Felix Werner
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, 94315, Straubing, Germany
| | - Lynn S Schwardmann
- Genetics of Prokaryotes, Faculty of Biology and CeBiTec, Bielefeld University, Bielefeld, Germany
| | - Daniel Siebert
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, 94315, Straubing, Germany
- SynBiofoundry@TUM, Technical University of Munich, Straubing, Germany
| | | | - Jörn Kalinowski
- Microbial Genomics and Biotechnology, CeBiTec, Bielefeld University, Bielefeld, Germany
| | - Marie-Theres Wirth
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, 94315, Straubing, Germany
| | - Katharina Hofer
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany
| | - Ralf Takors
- Institute of Biochemical Engineering, University of Stuttgart, Stuttgart, Germany
| | - Volker F Wendisch
- Genetics of Prokaryotes, Faculty of Biology and CeBiTec, Bielefeld University, Bielefeld, Germany
| | - Bastian Blombach
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, 94315, Straubing, Germany.
- SynBiofoundry@TUM, Technical University of Munich, Straubing, Germany.
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Takeno S, Hirata Y, Kitamura K, Ohtake T, Aoki K, Murata N, Hayashi M, Ikeda M. Metabolic engineering to produce palmitic acid or palmitoleic acid in an oleic acid-producing Corynebacterium glutamicum strain. Metab Eng 2023; 78:148-158. [PMID: 37286071 DOI: 10.1016/j.ymben.2023.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 05/14/2023] [Accepted: 06/04/2023] [Indexed: 06/09/2023]
Abstract
Focusing on the differences in the catalytic properties of two type I fatty acid synthases FasA and FasB, the fasA gene was disrupted in an oleic acid-producing Corynebacterium glutamicum strain. The resulting oleic acid-requiring strain whose fatty acid synthesis depends only on FasB exhibited almost exclusive production (217 mg/L) of palmitic acid (C16:0) from 1% glucose under the conditions supplemented with the minimum concentration of sodium oleate for growth. Plasmid-mediated amplification of fasB led to a 1.47-fold increase in palmitic acid production (320 mg/L), while fasB disruption resulted in no fatty acid production, with excretion of malonic acid (30 mg/L). Next, aiming at conversion of the palmitic acid producer to a producer of palmitoleic acid (POA, C16:1Δ9), we introduced the Pseudomonas nitroreducens Δ9-desaturase genes desBC into the palmitic acid producer. Although this resulted in failure, we noticed the emergence of suppressor mutants that exhibited the oleic acid-non-requiring phenotype. Production experiments revealed that one such mutant M-1 undoubtedly produced POA (17 mg/L) together with palmitic acid (173 mg/L). Whole genomic analysis and subsequent genetic analysis identified the suppressor mutation of strain M-1 as a loss-of-function mutation for the DtxR protein, a global regulator of iron metabolism. Considering that DesBC are both iron-containing enzymes, we investigated the conditions for increased iron availability to improve the DesBC-dependent conversion ratio of palmitic acid to POA. Eventually, supplementation of both hemin and the iron chelator protocatechuic acid in the engineered strain dramatically enhanced POA production to 161 mg/L with a conversion ratio of 80.1%. Cellular fatty acid analysis revealed that the POA-producing cells were really equipped with unnatural membrane lipids comprised predominantly of palmitic acid (85.1% of total cellular fatty acids), followed by non-native POA (12.4%).
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Affiliation(s)
- Seiki Takeno
- Department of Agricultural and Life Sciences, Faculty of Agriculture, Shinshu University, Nagano, Japan
| | - Yosuke Hirata
- Department of Agricultural and Life Sciences, Faculty of Agriculture, Shinshu University, Nagano, Japan
| | - Kako Kitamura
- Department of Agricultural and Life Sciences, Faculty of Agriculture, Shinshu University, Nagano, Japan
| | - Tatsunori Ohtake
- Department of Agricultural and Life Sciences, Faculty of Agriculture, Shinshu University, Nagano, Japan
| | - Kuniyoshi Aoki
- Department of Agricultural and Life Sciences, Faculty of Agriculture, Shinshu University, Nagano, Japan
| | - Noriko Murata
- Department of Agricultural and Life Sciences, Faculty of Agriculture, Shinshu University, Nagano, Japan
| | - Mikiro Hayashi
- Bioprocess Development Center, Kyowa Hakko Bio Co., Ltd., Tsukuba, Ibaraki, Japan
| | - Masato Ikeda
- Department of Agricultural and Life Sciences, Faculty of Agriculture, Shinshu University, Nagano, Japan.
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Parusnath M, Naidoo Y, Singh M, Kianersi F, Dewir YH. Antioxidant and Antibacterial Activities of the Leaf and Stem Extracts of Combretum molle (R. Br. ex G. Don.) Engl. & Diels. PLANTS (BASEL, SWITZERLAND) 2023; 12:plants12091757. [PMID: 37176814 PMCID: PMC10180969 DOI: 10.3390/plants12091757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 04/20/2023] [Accepted: 04/22/2023] [Indexed: 05/15/2023]
Abstract
Medicinal plants offer reasonable and accessible alternatives to synthetic drugs and are often devoid of the adverse side effects, toxicity, and pathogenic resistance associated with synthetic medicine. Combretum molle has been utilized in African traditional medicinal practices and purportedly contains bioactive compounds with medicinally beneficial effects. This study investigated the hexane, chloroform, and methanol leaf and stem extracts for their antioxidant properties using the 2,2'-diphenyl-1-picrylhydrazyl radical scavenging and ferric-reducing antioxidant power assays. The study additionally analyzed the methanol extracts for their antibacterial activity against Gram-negative Escherichia coli (ATCC 25922) and Gram-positive Staphylococcus aureus (ATCC 25923) bacteria using agar well diffusion. Relative to the scavenging activity of the ascorbic acid control (79.15 ± 0.63% at 15 µg/mL to 94.61 ± 0.12% at 240 µg/mL), the plant's radical scavenging activities were exceptionally high in the methanolic leaf and stem extracts (p < 0.05), ranging from 94.58 ± 1.10% at 15 µg/mL to 99.22 ± 0.30% at 240 µg/mL and 91.57 ± 1.71% at 15 µg/mL to 99.60 ± 0.20% at 240 µg/mL, respectively, suggesting a strong capacity to donate hydrogen ions. High scavenging activities were additionally observed in the chloroform stem (78.68 ± 1.18% at 15 µg/mL to 98.14 ± 1.22% at 240 µg/mL) and hexane leaf (72.12 ± 4.38% at 15 µg/mL to 89.87 ± 1.50% at 240 µg/mL) extracts (p < 0.05). All extracts exhibited poor ferric-reducing abilities in relation to the gallic acid control (100 ± 0.00%) at all concentrations (p < 0.05). The leaf and stem extracts exhibited broad-spectrum antibiotic capabilities against both tested strains, with significant activity at higher concentrations (p < 0.05). Overall, both the leaf and stem extracts of C. molle exhibited similar antioxidant and antibacterial activities. These findings warrant further pharmacological research on C. molle for potential drug development.
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Affiliation(s)
- Myuri Parusnath
- School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa
| | - Yougasphree Naidoo
- School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa
| | - Moganavelli Singh
- School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa
| | - Farzad Kianersi
- School of Environmental Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Yaser Hassan Dewir
- Plant Production Department, College of Food and Agriculture Sciences, King Saud University, Riyadh 11451, Saudi Arabia
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Gui JY, Rao S, Huang X, Liu X, Cheng S, Xu F. Interaction between selenium and essential micronutrient elements in plants: A systematic review. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 853:158673. [PMID: 36096215 DOI: 10.1016/j.scitotenv.2022.158673] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 09/04/2022] [Accepted: 09/07/2022] [Indexed: 06/15/2023]
Abstract
Nutrient imbalance (i.e., deficiency and toxicity) of microelements is an outstanding environmental issue that influences each aspect of ecosystems. Although the crucial roles of microelements in entire lifecycle of plants have been widely acknowledged, the effective control of microelements is still neglected due to the narrow safe margins. Selenium (Se) is an essential element for humans and animals. Although it is not believed to be indispensable for plants, many literatures have reported the significance of Se in terms of the uptake, accumulation, and detoxification of essential microelements in plants. However, most papers only concerned on the antagonistic effect of Se on metal elements in plants and ignored the underlying mechanisms. There is still a lack of systematic review articles to summarize the comprehensive knowledge on the connections between Se and microelements in plants. In this review, we conclude the bidirectional effects of Se on micronutrients in plants, including iron, zinc, copper, manganese, nickel, molybdenum, sodium, chlorine, and boron. The regulatory mechanisms of Se on these micronutrients are also analyzed. Moreover, we further emphasize the role of Se in alleviating element toxicity and adjusting the concentration of micronutrients in plants by altering the soil conditions (e.g., adsorption, pH, and organic matter), promoting microbial activity, participating in vital physiological and metabolic processes, generating element competition, stimulating metal chelation, organelle compartmentalization, and sequestration, improving the antioxidant defense system, and controlling related genes involved in transportation and tolerance. Based on the current understanding of the interaction between Se and these essential elements, future directions for research are suggested.
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Affiliation(s)
- Jia-Ying Gui
- College of Horticulture and Gardening, Yangtze University, Jingzhou 434025, China
| | - Shen Rao
- School of Modern Industry for Selenium Science and Engineering, National R&D Center for Se-rich Agricultural Products Processing Technology, Wuhan Polytechnic University, Wuhan 430023, China
| | - Xinru Huang
- College of Horticulture and Gardening, Yangtze University, Jingzhou 434025, China
| | - Xiaomeng Liu
- School of Modern Industry for Selenium Science and Engineering, National R&D Center for Se-rich Agricultural Products Processing Technology, Wuhan Polytechnic University, Wuhan 430023, China
| | - Shuiyuan Cheng
- School of Modern Industry for Selenium Science and Engineering, National R&D Center for Se-rich Agricultural Products Processing Technology, Wuhan Polytechnic University, Wuhan 430023, China.
| | - Feng Xu
- College of Horticulture and Gardening, Yangtze University, Jingzhou 434025, China.
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Thoma F, Schulze C, Gutierrez-Coto C, Hädrich M, Huber J, Gunkel C, Thoma R, Blombach B. Metabolic engineering of Vibrio natriegens for anaerobic succinate production. Microb Biotechnol 2021; 15:1671-1684. [PMID: 34843164 PMCID: PMC9151343 DOI: 10.1111/1751-7915.13983] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 01/14/2023] Open
Abstract
The biotechnological production of succinate bears serious potential to fully replace existing petrochemical approaches in the future. In order to establish an economically viable bioprocess, obtaining high titre, yield and productivity is of central importance. In this study, we present a straightforward engineering approach for anaerobic succinate production with Vibrio natriegens, consisting of essential metabolic engineering and optimization of process conditions. The final producer strain V. natriegens Δlldh Δdldh Δpfl Δald Δdns::pycCg (Succ1) yielded 1.46 mol of succinate per mol of glucose under anaerobic conditions (85% of the theoretical maximum) and revealed a particularly high biomass‐specific succinate production rate of 1.33 gSucc gCDW−1 h−1 compared with well‐established production systems. By applying carbon and redox balancing, we determined the intracellular flux distribution and show that under the tested conditions the reductive TCA as well as the oxidative TCA/glyoxylate pathway contributed to succinate formation. In a zero‐growth bioprocess using minimal medium devoid of complex additives and expensive supplements, we obtained a final titre of 60.4 gSucc l−1 with a maximum productivity of 20.8 gSucc l−1 h−1 and an overall volumetric productivity of 8.6 gSucc l−1 h−1 during the 7 h fermentation. The key performance indicators (titre, yield and productivity) of this first engineering approach in V. natriegens are encouraging and compete with costly tailored microbial production systems.
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Affiliation(s)
- Felix Thoma
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, Straubing, 94315, Germany.,SynBiofoundry@TUM, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Schulgasse 22, Straubing, 94315, Germany
| | - Clarissa Schulze
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, Straubing, 94315, Germany
| | - Carolina Gutierrez-Coto
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, Straubing, 94315, Germany
| | - Maurice Hädrich
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, Straubing, 94315, Germany
| | - Janine Huber
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, Straubing, 94315, Germany
| | - Christoph Gunkel
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, Straubing, 94315, Germany
| | - Rebecca Thoma
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, Straubing, 94315, Germany
| | - Bastian Blombach
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Uferstraße 53, Straubing, 94315, Germany.,SynBiofoundry@TUM, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Schulgasse 22, Straubing, 94315, Germany
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Meena BI, Lakk-Bogáth D, Keszei S, Kaizer J. Bleach catalysis in aqueous medium by iron(III)-isoindoline complexes and hydrogen peroxide. CR CHIM 2021. [DOI: 10.5802/crchim.112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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8
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Siebert D, Altenbuchner J, Blombach B. A Timed Off-Switch for Dynamic Control of Gene Expression in Corynebacterium Glutamicum. Front Bioeng Biotechnol 2021; 9:704681. [PMID: 34395409 PMCID: PMC8358305 DOI: 10.3389/fbioe.2021.704681] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 06/30/2021] [Indexed: 11/13/2022] Open
Abstract
Dynamic control of gene expression mainly relies on inducible systems, which require supplementation of (costly) inducer molecules. In contrast, synthetic regulatory circuits, which allow the timed shutdown of gene expression, are rarely available and therefore represent highly attractive tools for metabolic engineering. To achieve this, we utilized the VanR/P vanABK * regulatory system of Corynebacterium glutamicum, which consists of the transcriptional repressor VanR and a modified promoter of the vanABK operon (P vanABK *). VanR activity is modulated by one of the phenolic compounds ferulic acid, vanillin or vanillic acid, which are co-metabolized with d-glucose. Thus, gene expression in the presence of d-glucose is turned off if one of the effector molecules is depleted from the medium. To dynamically control the expression of the aceE gene, encoding the E1 subunit of the pyruvate dehydrogenase complex that is essential for growth on d-glucose, we replaced the native promoter by vanR/P vanABK * yielding C. glutamicum ΔP aceE ::vanR-P vanABK *. The biomass yield of this strain increased linearly with the supplemented amount of effector. After consumption of the phenolic compounds growth ceased, however, C. glutamicumΔP aceE ::vanR-P vanABK * continued to utilize the residual d-glucose to produce significant amounts of pyruvate, l-alanine, and l-valine. Interestingly, equimolar concentrations of the three phenolic compounds resulted in different biomass yields; and with increasing effector concentration, the product spectrum shifted from pyruvate over l-alanine to l-valine. To further test the suitability of the VanR/P vanABK * system, we overexpressed the l-valine biosynthesis genes ilvBNCE in C. glutamicum ΔP aceE ::vanR-P vanABK *, which resulted in efficient l-valine production with a yield of about 0.36 mol l-valine per mol d-glucose. These results demonstrate that the VanR/P vanABK * system is a valuable tool to control gene expression in C. glutamicum in a timed manner by the cheap and abundant phenolic compounds ferulic acid, vanillin, and vanillic acid.
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Affiliation(s)
- Daniel Siebert
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Straubing, Germany
- SynBiofoundry@TUM, Technical University of Munich, Straubing, Germany
| | - Josef Altenbuchner
- Institute of Industrial Genetics, University of Stuttgart, Stuttgart, Germany
| | - Bastian Blombach
- Microbial Biotechnology, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Straubing, Germany
- SynBiofoundry@TUM, Technical University of Munich, Straubing, Germany
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9
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Physiological Response of Corynebacterium glutamicum to Indole. Microorganisms 2020; 8:microorganisms8121945. [PMID: 33302489 PMCID: PMC7764795 DOI: 10.3390/microorganisms8121945] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/04/2020] [Accepted: 12/05/2020] [Indexed: 12/20/2022] Open
Abstract
The aromatic heterocyclic compound indole is widely spread in nature. Due to its floral odor indole finds application in dairy, flavor, and fragrance products. Indole is an inter- and intracellular signaling molecule influencing cell division, sporulation, or virulence in some bacteria that synthesize it from tryptophan by tryptophanase. Corynebacterium glutamicum that is used for the industrial production of amino acids including tryptophan lacks tryptophanase. To test if indole is metabolized by C. glutamicum or has a regulatory role, the physiological response to indole by this bacterium was studied. As shown by RNAseq analysis, indole, which inhibited growth at low concentrations, increased expression of genes involved in the metabolism of iron, copper, and aromatic compounds. In part, this may be due to iron reduction as indole was shown to reduce Fe3+ to Fe2+ in the culture medium. Mutants with improved tolerance to indole were selected by adaptive laboratory evolution. Among the mutations identified by genome sequencing, mutations in three transcriptional regulator genes were demonstrated to be causal for increased indole tolerance. These code for the regulator of iron homeostasis DtxR, the regulator of oxidative stress response RosR, and the hitherto uncharacterized Cg3388. Gel mobility shift analysis revealed that Cg3388 binds to the intergenic region between its own gene and the iolT2-rhcM2D2 operon encoding inositol uptake system IolT2, maleylacetate reductase, and catechol 1,2-dioxygenase. Increased RNA levels of rhcM2 in a cg3388 deletion strain indicated that Cg3388 acts as repressor. Indole, hydroquinone, and 1,2,4-trihydroxybenzene may function as inducers of the iolT2-rhcM2D2 operon in vivo as they interfered with DNA binding of Cg3388 at physiological concentrations in vitro. Cg3388 was named IhtR.
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