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Ozsefil IC, Miraloglu IH, Ozbayram EG, Ince B, Ince O. Bioaugmentation of anaerobic digesters with the enriched lignin-degrading microbial consortia through a metagenomic approach. CHEMOSPHERE 2024; 355:141831. [PMID: 38561162 DOI: 10.1016/j.chemosphere.2024.141831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Revised: 03/25/2024] [Accepted: 03/26/2024] [Indexed: 04/04/2024]
Abstract
The recalcitrance of lignin impedes the efficient utilization of lignocellulosic biomass, hindering the efficient production of biogas and value-added materials. Despite the emergence of anaerobic digestion as a superior alternative to the aerobic method for lignin processing, achieving its feasibility requires thorough characterization of lignin-degrading anaerobic microorganisms, assessment of their biomethane production potential, and a comprehensive understanding of the degradation pathway. This study aimed to address the aforementioned necessities by bioaugmenting seed sludge with three distinct enriched lignin-degrading microbial consortia at both 25 °C and 37 °C. Enhanced biomethane yields was detected in the bioaugmented digesters, while the highest production was observed as 188 mLN CH4 gVS-1 in digesters operated at 37 °C. Moreover, methane yield showed a significant improvement in the samples at 37 °C ranging from 110% to 141% compared to the control, demonstrating the efficiency of the enriched lignin-degrading microbial community. Temperature and substrate were identified as key factors influencing microbial community dynamics. The observation that microbial communities tended to revert to the initial state after lignin depletion, indicating the stability of the overall microbiota composition in the digesters, is a promising finding for large-scale studies. Noteworthy candidates for lignin degradation, including Sporosarcina psychrophila, Comamonas aquatica, Shewanella baltica, Pseudomonas sp. C27, and Brevefilum fermentans were identified in the bioaugmented samples. PICRUSt2 predictions suggest that the pathway and specific proteins involved in anaerobic lignin degradation might share similarities with those engaged in the degradation of aromatic compounds.
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Affiliation(s)
- Ibrahim Cem Ozsefil
- Bogazici University, Institute of Environmental Sciences, Bebek, 34342, Istanbul, Turkey
| | | | - E Gozde Ozbayram
- Istanbul University, Faculty of Aquatic Sciences, Department of Marine and Freshwater Resources Management, Fatih, 34134, Istanbul, Turkey
| | - Bahar Ince
- Bogazici University, Institute of Environmental Sciences, Bebek, 34342, Istanbul, Turkey
| | - Orhan Ince
- Department of Environmental Engineering, Faculty of Civil Engineering, Istanbul Technical University, Maslak, 34396, Istanbul, Turkey
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Zhang Z, Ran H, Hua Y, Deng F, Zeng B, Chai J, Li Y. Screening and evaluation of skin potential probiotic from high-altitude Tibetans to repair ultraviolet radiation damage. Front Microbiol 2023; 14:1273902. [PMID: 37928688 PMCID: PMC10620709 DOI: 10.3389/fmicb.2023.1273902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 09/29/2023] [Indexed: 11/07/2023] Open
Abstract
Human skin microbes play critical roles in skin health and diseases. Microbes colonizing on the skin of Tibetans living in the high-altitude area for generations may have a stronger ability to resist the harsh environment, such as high ultraviolet radiation (UV). Isolation of a potential probiotic from Tibetans skin is beneficial for resistance of skin disease for humans in the world. In this study, the signature microbiota for Tibetan skin were characterized compared to low-altitude humans. Next, using culture-omics, 118 species were isolated. The culturability of high-altitude of Tibetan skin microbiome reached approximate 66.8%. Next, we found that one strain, Pantoea eucrina, had the greatest ability to repair UV damage to the skin as the lowest pathological score was observed in this group. Interestingly, another animal trial found this bacterium resisted UV rather than its metabolites. Using whole genome sequencing, this strain P. eucrina KBFS172 was confirmed, and its functions were annotated. It might involve in the metabolic pathway of carotenoid biosynthesis with anti-oxidative stress properties, which plays critical roles in UV-damage repair. In conclusion, we characterized the signature microbes of skin in high-altitude Tibetans, isolated a skin bacterium of Pantoea eucrina KBFS172 which could repair UV damage via involving the metabolic pathway of carotenoid biosynthesis. Our results provide a new potential skin probiotic for skin disease prevention or sunburn.
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Affiliation(s)
- Zhihao Zhang
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, College of Life Science and Engineering, Foshan University, Foshan, China
- School of Life Science and Engineering, Foshan University, Foshan, China
| | - Haixia Ran
- Animal Husbandry and Fisheries Technology Extension Station, Chongqing, China
| | - Yutong Hua
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, China
| | - Feilong Deng
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, College of Life Science and Engineering, Foshan University, Foshan, China
- School of Life Science and Engineering, Foshan University, Foshan, China
| | - Bo Zeng
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, China
| | - Jianmin Chai
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, College of Life Science and Engineering, Foshan University, Foshan, China
- School of Life Science and Engineering, Foshan University, Foshan, China
| | - Ying Li
- Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, College of Life Science and Engineering, Foshan University, Foshan, China
- School of Life Science and Engineering, Foshan University, Foshan, China
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Stante M, Weiland-Bräuer N, Repnik U, Werner A, Bramkamp M, Chibani CM, Schmitz RA. Four Novel Caudoviricetes Bacteriophages Isolated from Baltic Sea Water Infect Colonizers of Aurelia aurita. Viruses 2023; 15:1525. [PMID: 37515211 PMCID: PMC10383413 DOI: 10.3390/v15071525] [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: 06/14/2023] [Revised: 07/04/2023] [Accepted: 07/06/2023] [Indexed: 07/30/2023] Open
Abstract
The moon jellyfish Aurelia aurita is associated with a highly diverse microbiota changing with provenance, tissue, and life stage. While the crucial relevance of bacteria to host fitness is well known, bacteriophages have often been neglected. Here, we aimed to isolate virulent phages targeting bacteria that are part of the A. aurita-associated microbiota. Four phages (Pseudomonas phage BSwM KMM1, Citrobacter phages BSwM KMM2-BSwM KMM4) were isolated from the Baltic Sea water column and characterized. Phages KMM2/3/4 infected representatives of Citrobacter, Shigella, and Escherichia (Enterobacteriaceae), whereas KMM1 showed a remarkably broad host range, infecting Gram-negative Pseudomonas as well as Gram-positive Staphylococcus. All phages showed an up to 99% adsorption to host cells within 5 min, short latent periods (around 30 min), large burst sizes (mean of 128 pfu/cell), and high efficiency of plating (EOP > 0.5), demonstrating decent virulence, efficiency, and infectivity. Transmission electron microscopy and viral genome analysis revealed that all phages are novel species and belong to the class of Caudoviricetes harboring a tail and linear double-stranded DNA (formerly known as Siphovirus-like (KMM3) and Myovirus-like (KMM1/2/4) bacteriophages) with genome sizes between 50 and 138 kbp. In the future, these isolates will allow manipulation of the A. aurita-associated microbiota and provide new insights into phage impact on the multicellular host.
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Affiliation(s)
- Melissa Stante
- Institute for General Microbiology, Christian Albrechts University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany; (M.S.); (N.W.-B.); (A.W.); (M.B.); (C.M.C.)
| | - Nancy Weiland-Bräuer
- Institute for General Microbiology, Christian Albrechts University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany; (M.S.); (N.W.-B.); (A.W.); (M.B.); (C.M.C.)
| | - Urska Repnik
- Central Microscopy Facility, Christian Albrechts University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany;
| | - Almut Werner
- Institute for General Microbiology, Christian Albrechts University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany; (M.S.); (N.W.-B.); (A.W.); (M.B.); (C.M.C.)
| | - Marc Bramkamp
- Institute for General Microbiology, Christian Albrechts University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany; (M.S.); (N.W.-B.); (A.W.); (M.B.); (C.M.C.)
- Central Microscopy Facility, Christian Albrechts University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany;
| | - Cynthia M. Chibani
- Institute for General Microbiology, Christian Albrechts University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany; (M.S.); (N.W.-B.); (A.W.); (M.B.); (C.M.C.)
| | - Ruth A. Schmitz
- Institute for General Microbiology, Christian Albrechts University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany; (M.S.); (N.W.-B.); (A.W.); (M.B.); (C.M.C.)
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Systems metabolic engineering upgrades Corynebacterium glutamicum to high-efficiency cis, cis-muconic acid production from lignin-based aromatics. Metab Eng 2023; 75:153-169. [PMID: 36563956 DOI: 10.1016/j.ymben.2022.12.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 12/14/2022] [Accepted: 12/17/2022] [Indexed: 12/24/2022]
Abstract
Lignin displays a highly challenging renewable. To date, massive amounts of lignin, generated in lignocellulosic processing facilities, are for the most part merely burned due to lacking value-added alternatives. Aromatic lignin monomers of recognized relevance are in particular vanillin, and to a lesser extent vanillate, because they are accessible at high yield from softwood-lignin using industrially operated alkaline oxidative depolymerization. Here, we metabolically engineered C. glutamicum towards cis, cis-muconate (MA) production from these key aromatics. Starting from the previously created catechol-based producer C. glutamicum MA-2, systems metabolic engineering first discovered an unspecific aromatic aldehyde reductase that formed aromatic alcohols from vanillin, protocatechualdehyde, and p- hydroxybenzaldehyde, and was responsible for the conversion up to 57% of vanillin into vanillyl alcohol. The alcohol was not re-consumed by the microbe later, posing a strong drawback on the producer. The identification and subsequent elimination of the encoding fudC gene completely abolished vanillyl alcohol formation. Second, the initially weak flux through the native vanillin and vanillate metabolism was enhanced up to 2.9-fold by implementing synthetic pathway modules. Third, the most efficient protocatechuate decarboxylase AroY for conversion of the midstream pathway intermediate protocatechuate into catechol was identified out of several variants in native and codon optimized form and expressed together with the respective helper proteins. Fourth, the streamlined modules were all genomically combined which yielded the final strain MA-9. MA-9 produced bio-based MA from vanillin, vanillate, and seven structurally related aromatics at maximum selectivity. In addition, MA production from softwood-based vanillin, obtained through alkaline depolymerization, was demonstrated.
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Rammala B, Zhou N. Looking into the world's largest elephant population in search of ligninolytic microorganisms for biorefineries: a mini-review. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2022; 15:64. [PMID: 35689287 PMCID: PMC9188235 DOI: 10.1186/s13068-022-02159-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 05/12/2022] [Indexed: 11/24/2022]
Abstract
Gastrointestinal tracts (GIT) of herbivores are lignin-rich environments with the potential to find ligninolytic microorganisms. The occurrence of the microorganisms in herbivore GIT is a well-documented mutualistic relationship where the former benefits from the provision of nutrients and the latter benefits from the microorganism-assisted digestion of their recalcitrant lignin diets. Elephants are one of the largest herbivores that rely on the microbial anaerobic fermentation of their bulky recalcitrant low-quality forage lignocellulosic diet given their inability to break down major components of plant cells. Tapping the potential of these mutualistic associations in the biggest population of elephants in the whole world found in Botswana is attractive in the valorisation of the bulky recalcitrant lignin waste stream generated from the pulp and paper, biofuel, and agro-industries. Despite the massive potential as a feedstock for industrial fermentations, few microorganisms have been commercialised. This review focuses on the potential of microbiota from the gastrointestinal tract and excreta of the worlds' largest population of elephants of Botswana as a potential source of extremophilic ligninolytic microorganisms. The review further discusses the recalcitrance of lignin, achievements, limitations, and challenges with its biological depolymerisation. Methods of isolation of microorganisms from elephant dung and their improvement as industrial strains are further highlighted.
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Affiliation(s)
- Bame Rammala
- Department of Biological Sciences and Biotechnology, Botswana International University of Science and Technology, Private Bag 16, Palapye, Botswana.
| | - Nerve Zhou
- Department of Biological Sciences and Biotechnology, Botswana International University of Science and Technology, Private Bag 16, Palapye, Botswana.
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Margesin R, Ludwikowski TM, Kutzner A, Wagner AO. Low-Temperature Biodegradation of Lignin-Derived Aromatic Model Monomers by the Cold-Adapted Yeast Rhodosporidiobolus colostri Isolated from Alpine Forest Soil. Microorganisms 2022; 10:microorganisms10030515. [PMID: 35336090 PMCID: PMC8955795 DOI: 10.3390/microorganisms10030515] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 01/12/2023] Open
Abstract
The contribution of cold-adapted yeasts to the emerging field of lignin biovalorization has not yet been studied. The red-pigmented basidiomycetous yeast strain Rhodosporidiobolus colostri DBVPG 10655 was examined for its potential to degrade five selected lignin-derived aromatic monomers (syringic acid, p-coumaric acid, 4-hydroxybenzoic acid, ferulic acid, and vanillic acid). The strain utilized p-coumaric acid, 4-hydroxybenzoic acid, and ferulic acid not only as the sole carbon source; full biodegradation occurred also in mixtures of multiple monomers. Vanillic acid was not utilized as the sole carbon source, but was degraded in the presence of p-coumaric acid, 4-hydroxybenzoic acid, and ferulic acid. Syringic acid was utilized neither as the sole carbon source nor in mixtures of compounds. Biodegradation of lignin-derived aromatic monomers was detected over a broad temperature range (1–25 °C), which is of ecological significance and of biotechnological relevance.
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A novel Bacillus ligniniphilus catechol 2,3-dioxygenase shows unique substrate preference and metal requirement. Sci Rep 2021; 11:23982. [PMID: 34907211 PMCID: PMC8671467 DOI: 10.1038/s41598-021-03144-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 11/26/2021] [Indexed: 12/03/2022] Open
Abstract
Identification of novel enzymes from lignin degrading microorganisms will help to develop biotechnologies for biomass valorization and aromatic hydrocarbons degradation. Bacillus ligniniphilus L1 grows with alkaline lignin as the single carbon source and is a great candidate for ligninolytic enzyme identification. The first dioxygenase from strain L1 was heterologously expressed, purified, and characterized with an optimal temperature and pH of 32.5 °C and 7.4, respectively. It showed the highest activity with 3-ethylcatechol and significant activities with other substrates in the decreasing order of 3-ethylcatechol > 3-methylcatechol > 3-isopropyl catechol > 2, 3-dihydroxybiphenyl > 4-methylcatechol > catechol. It did not show activities against other tested substrates with similar structures. Most reported catechol 2,3-dioxygenases (C23Os) are Fe2+-dependent whereas Bacillus ligniniphilus catechol 2,3-dioxygenase (BLC23O) is more Mn2+- dependent. At 1 mM, Mn2+ led to 230-fold activity increase and Fe2+ led to 22-fold increase. Sequence comparison and phylogenetic analyses suggested that BL23O is different from other Mn-dependent enzymes and uniquely grouped with an uncharacterized vicinal oxygen chelate (VOC) family protein from Paenibacillus apiaries. Gel filtration analysis showed that BLC23O is a monomer under native condition. This is the first report of a C23O from Bacillus ligniniphilus L1 with unique substrate preference, metal-dependency, and monomeric structure.
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Weiland F, Kohlstedt M, Wittmann C. Guiding stars to the field of dreams: Metabolically engineered pathways and microbial platforms for a sustainable lignin-based industry. Metab Eng 2021; 71:13-41. [PMID: 34864214 DOI: 10.1016/j.ymben.2021.11.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 11/25/2021] [Accepted: 11/29/2021] [Indexed: 12/19/2022]
Abstract
Lignin is an important structural component of terrestrial plants and is readily generated during biomass fractionation in lignocellulose processing facilities. Due to lacking alternatives the majority of technical lignins is industrially simply burned into heat and energy. However, regarding its vast abundance and a chemically interesting richness in aromatics, lignin is presently regarded as the most under-utilized and promising feedstock for value-added applications. Notably, microbes have evolved powerful enzymes and pathways that break down lignin and metabolize its various aromatic components. This natural pathway atlas meanwhile serves as a guiding star for metabolic engineers to breed designed cell factories and efficiently upgrade this global waste stream. The metabolism of aromatic compounds, in combination with success stories from systems metabolic engineering, as reviewed here, promises a sustainable product portfolio from lignin, comprising bulk and specialty chemicals, biomaterials, and fuels.
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Affiliation(s)
- Fabia Weiland
- Institute of Systems Biotechnology, Saarland University, Saarbrücken, Germany
| | - Michael Kohlstedt
- Institute of Systems Biotechnology, Saarland University, Saarbrücken, Germany
| | - Christoph Wittmann
- Institute of Systems Biotechnology, Saarland University, Saarbrücken, Germany.
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Margesin R, Volgger G, Wagner AO, Zhang D, Poyntner C. Biodegradation of lignin monomers and bioconversion of ferulic acid to vanillic acid by Paraburkholderia aromaticivorans AR20-38 isolated from Alpine forest soil. Appl Microbiol Biotechnol 2021; 105:2967-2977. [PMID: 33687503 PMCID: PMC8007519 DOI: 10.1007/s00253-021-11215-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 02/10/2021] [Accepted: 02/28/2021] [Indexed: 11/24/2022]
Abstract
Abstract Lignin bio-valorization is an emerging field of applied biotechnology and has not yet been studied at low temperatures. Paraburkholderia aromaticivorans AR20-38 was examined for its potential to degrade six selected lignin monomers (syringic acid, p-coumaric acid, 4-hydroxybenzoic acid, ferulic acid, vanillic acid, benzoic acid) from different upper funneling aromatic pathways. The strain degraded four of these compounds at 10°C, 20°C, and 30°C; syringic acid and vanillic acid were not utilized as sole carbon source. The degradation of 5 mM and 10 mM ferulic acid was accompanied by the stable accumulation of high amounts of the value-added product vanillic acid (85–89% molar yield; 760 and 1540 mg l−1, respectively) over the whole temperature range tested. The presence of essential genes required for reactions in the upper funneling pathways was confirmed in the genome. This is the first report on biodegradation of lignin monomers and the stable vanillic acid production at low and moderate temperatures by P. aromaticivorans. Key points • Paraburkholderia aromaticivorans AR20-38 successfully degrades four lignin monomers. • Successful degradation study at low (10°C) and moderate temperatures (20–30°C). • Biotechnological value: high yield of vanillic acid produced from ferulic acid.
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Affiliation(s)
- Rosa Margesin
- Institute of Microbiology, University of Innsbruck, Technikerstrasse 25, 6020, Innsbruck, Austria.
| | - Georg Volgger
- Institute of Microbiology, University of Innsbruck, Technikerstrasse 25, 6020, Innsbruck, Austria
| | - Andreas O Wagner
- Institute of Microbiology, University of Innsbruck, Technikerstrasse 25, 6020, Innsbruck, Austria
| | - Dechao Zhang
- Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Caroline Poyntner
- Institute of Microbiology, University of Innsbruck, Technikerstrasse 25, 6020, Innsbruck, Austria
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Kumar M, You S, Beiyuan J, Luo G, Gupta J, Kumar S, Singh L, Zhang S, Tsang DCW. Lignin valorization by bacterial genus Pseudomonas: State-of-the-art review and prospects. BIORESOURCE TECHNOLOGY 2021; 320:124412. [PMID: 33249259 DOI: 10.1016/j.biortech.2020.124412] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 11/08/2020] [Accepted: 11/11/2020] [Indexed: 06/12/2023]
Abstract
The most prominent aromatic feedstock on Earth is lignin, however, lignin valorization is still an underrated subject. The principal preparatory strategies for lignin valorization are fragmentation and depolymerization which help in the production of fuels and chemicals. Owing to lignin's structural heterogeneity, these strategies result in product generation which requires tedious separation and purification to extract target products. The bacterial genus Pseudomonas has been dominant for its lignin valorization potency, owing to a robust enzymatic machinery that is used to funnel variable lignin derivatives into certain target products such as polyhydroxyalkanotes (PHAs) and cis, cis-muconic acid (MA). In this review, the potential of genus Pseudomonas in lignin valorization is critically reviewed along with the advanced genetic techniques and tools to ease the use of lignin/lignin-model compounds for the synthesis of bioproducts. This review also highlights the research gaps in lignin biovalorization and discuss the challenges and possibilities for future research.
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Affiliation(s)
- Manish Kumar
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; CSIR - National Environmental and Engineering Research Institute (CSIR-NEERI), Nagpur 440 020, India
| | - Siming You
- University of Glasgow, James Watt School of Engineering, Glasgow G12 8 QQ, United Kingdom
| | - Jingzi Beiyuan
- Biochar Engineering Technology Research Center of Guangdong Province, School of Environment and Chemical Engineering, Foshan University, Foshan 528000, China
| | - Gang Luo
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Juhi Gupta
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Sunil Kumar
- CSIR - National Environmental and Engineering Research Institute (CSIR-NEERI), Nagpur 440 020, India
| | - Lal Singh
- CSIR - National Environmental and Engineering Research Institute (CSIR-NEERI), Nagpur 440 020, India
| | - Shicheng Zhang
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Daniel C W Tsang
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
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Vanillin Production in Pseudomonas: Whole-Genome Sequencing of Pseudomonas sp. Strain 9.1 and Reannotation of Pseudomonas putida CalA as a Vanillin Reductase. Appl Environ Microbiol 2020; 86:AEM.02442-19. [PMID: 31924622 PMCID: PMC7054097 DOI: 10.1128/aem.02442-19] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 12/21/2019] [Indexed: 02/06/2023] Open
Abstract
Microbial degradation of lignin and its related aromatic compounds has great potential for the sustainable production of chemicals and bioremediation of contaminated soils. We previously isolated Pseudomonas sp. strain 9.1 from historical waste deposits (forming so-called fiber banks) released from pulp and paper mills along the Baltic Sea coast. The strain accumulated vanillyl alcohol during growth on vanillin, and while reported in other microbes, this phenotype is less common in wild-type pseudomonads. As the reduction of vanillin to vanillyl alcohol is an undesired trait in Pseudomonas strains engineered to accumulate vanillin, connecting the strain 9.1 phenotype with a genotype would increase the fundamental understanding and genetic engineering potential of microbial vanillin metabolism. The genome of Pseudomonas sp. 9.1 was sequenced and assembled. Annotation identified oxidoreductases with homology to Saccharomyces cerevisiae alcohol dehydrogenase ScADH6p, known to reduce vanillin to vanillyl alcohol, in both the 9.1 genome and the model strain Pseudomonas putida KT2440. Recombinant expression of the Pseudomonas sp. 9.1 FEZ21_09870 and P. putida KT2440 PP_2426 (calA) genes in Escherichia coli revealed that these open reading frames encode aldehyde reductases that convert vanillin to vanillyl alcohol, and that P. putida KT2440 PP_3839 encodes a coniferyl alcohol dehydrogenase that oxidizes coniferyl alcohol to coniferyl aldehyde (i.e., the function previously assigned to calA). The deletion of PP_2426 in P. putida GN442 engineered to accumulate vanillin resulted in a decrease in by-product (vanillyl alcohol) yield from 17% to ∼1%. Based on these results, we propose the reannotation of PP_2426 and FEZ21_09870 as areA and PP_3839 as calA-II IMPORTANCE Valorization of lignocellulose (nonedible plant matter) is of key interest for the sustainable production of chemicals from renewable resources. Lignin, one of the main constituents of lignocellulose, is a heterogeneous aromatic biopolymer that can be chemically depolymerized into a heterogeneous mixture of aromatic building blocks; those can be further converted by certain microbes into value-added aromatic chemicals, e.g., the flavoring agent vanillin. We previously isolated a Pseudomonas sp. strain with the (for the genus) unusual trait of vanillyl alcohol production during growth on vanillin. Whole-genome sequencing of the isolate led to the identification of a vanillin reductase candidate gene whose deletion in a recombinant vanillin-accumulating P. putida strain almost completely alleviated the undesired vanillyl alcohol by-product yield. These results represent an important step toward biotechnological production of vanillin from lignin using bacterial cell factories.
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Morya R, Kumar M, Singh SS, Thakur IS. Genomic analysis of Burkholderia sp. ISTR5 for biofunneling of lignin-derived compounds. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:277. [PMID: 31788027 PMCID: PMC6880542 DOI: 10.1186/s13068-019-1606-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 10/29/2019] [Indexed: 05/25/2023]
Abstract
BACKGROUND Lignin is the second most abundant natural polymer on earth. Industries using lignocellulosic biomass as feedstock generate a considerable amount of lignin as a byproduct with minimal usage. For a sustainable biorefinery, the lignin must be utilized in improved ways. Lignin is recalcitrant to degradation due to the complex and heterogeneous structure. The depolymerization of lignin and its conversion into specific product stream are the major challenges associated with lignin valorization. The blend of oligomeric, dimeric and monomeric lignin-derived compounds (LDCs) generated during depolymerization can be utilized by microbes for production of bioproducts. RESULTS In the present study, a novel bacterium Burkholderia sp. strain ISTR5 (R5), a proteobacteria belonging to class betaproteobacteria, order Burkholderiales and family Burkholderiaceae, was isolated and characterized for the degradation of LDCs. R5 strain was cultured on 12 LDCs in mineral salt medium (MSM) supplemented with individual compounds such as syringic acid, p-coumaric acid, ferulic acid, vanillin, vanillic acid, guaiacol, 4-hydroxybenzoic acid, gallic acid, benzoic acid, syringaldehyde, veratryl alcohol and catechol. R5 was able to grow and utilize all the selected LDCs. The degradation of selected LDCs was monitored by bacterial growth, total organic carbon (TOC) removal and UV-Vis absorption spectra in scan mode. TOC reduction shown in the sample contains syringic acid 80.7%, ferulic acid 84.1%, p-coumaric acid 85.9% and benzoic acid 83.2%. In UV-Vis absorption spectral scan, most of the lignin-associated peaks were found at or near 280 nm wavelength in the obtained absorption spectra. Enzyme assay for the ligninolytic enzymes was also performed, and it was observed that lignin peroxidase and laccase were predominantly expressed. Furthermore, the GC-MS analysis of LDCs was performed to identify the degradation intermediates from these compounds. The genomic analysis showed the robustness of this strain and identified various candidate genes responsible for the degradation of aromatic or lignin derivatives, detoxification mechanism, oxidative stress response and fatty acid synthesis. The presence of peroxidases (13%), laccases (4%), monooxygenases (23%), dioxygenase (44%), NADPH: quinone oxidoreductases (16%) and many other related enzymes supported the degradation of LDCs. CONCLUSION Numerous pathway intermediates were observed during experiment. Vanillin was found during growth on syringic acid, ferulic acid and p-coumaric acid. Some other intermediates like catechol, acetovanillone, syringaldehyde and 3,4-dihydroxybenzaldehyde from the recognized bacterial metabolic pathways existed during growth on the LDCs. The ortho- and meta cleavage pathway enzymes, such as the catechol-1,2-dioxygenase, protocatechuate 3,4-dioxygenase, catechol-2,3-dioxygenase and toluene-2,3-dioxygenase, were observed in the genome. In addition to the common aromatic degradation pathways, presence of the epoxyqueuosine reductase, 1,2-epoxyphenylacetyl-CoA isomerase in the genome advocates that this strain may follow the epoxy Coenzyme A thioester pathway for degradation.
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Affiliation(s)
- Raj Morya
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
| | - Madan Kumar
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
| | - Shashi Shekhar Singh
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
| | - Indu Shekhar Thakur
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, 110067 India
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Ravi K, García-Hidalgo J, Brink DP, Skyvell M, Gorwa-Grauslund MF, Lidén G. Physiological characterization and sequence analysis of a syringate-consuming Actinobacterium. BIORESOURCE TECHNOLOGY 2019; 285:121327. [PMID: 30991184 DOI: 10.1016/j.biortech.2019.121327] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/05/2019] [Accepted: 04/06/2019] [Indexed: 06/09/2023]
Abstract
Hardwood lignin is made of up to 75% syringyl-units and the bioconversion of syringate and syringaldehyde is therefore of considerable interest for biological valorization of lignin. In the current study, we have isolated a syringate-consuming bacterium identified as Microbacterium sp. RG1 and characterized its growth on several lignin model compounds. Growth was observed on syringate, 3-O-methylgallate, vanillate, 4-hydroxybenzoate, ferulate and p-coumarate. Toxic aromatic aldehydes such as vanillin and syringaldehyde were converted to their respective alcohols/acids which were eventually consumed with a maximum specific uptake rate of 0.02 and 0.1 mmol (gCDW h)-1 respectively. The isolate was further subjected to whole genome sequencing and putative genes related to the metabolism of syringyl-compounds were mapped for the first time in a Gram-positive bacterium. These findings will be of high significance when designing future host microorganisms and bioprocesses for the efficient valorization of pre-treated lignin feedstocks.
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Affiliation(s)
- Krithika Ravi
- Department of Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Javier García-Hidalgo
- Division of Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Daniel P Brink
- Division of Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Martin Skyvell
- Department of Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Marie F Gorwa-Grauslund
- Division of Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Gunnar Lidén
- Department of Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
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Lubbers RJM, Dilokpimol A, Visser J, Mäkelä MR, Hildén KS, de Vries RP. A comparison between the homocyclic aromatic metabolic pathways from plant-derived compounds by bacteria and fungi. Biotechnol Adv 2019; 37:107396. [PMID: 31075306 DOI: 10.1016/j.biotechadv.2019.05.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 04/18/2019] [Accepted: 05/03/2019] [Indexed: 12/13/2022]
Abstract
Aromatic compounds derived from lignin are of great interest for renewable biotechnical applications. They can serve in many industries e.g. as biochemical building blocks for bioplastics or biofuels, or as antioxidants, flavor agents or food preservatives. In nature, lignin is degraded by microorganisms, which results in the release of homocyclic aromatic compounds. Homocyclic aromatic compounds can also be linked to polysaccharides, tannins and even found freely in plant biomass. As these compounds are often toxic to microbes already at low concentrations, they need to be degraded or converted to less toxic forms. Prior to ring cleavage, the plant- and lignin-derived aromatic compounds are converted to seven central ring-fission intermediates, i.e. catechol, protocatechuic acid, hydroxyquinol, hydroquinone, gentisic acid, gallic acid and pyrogallol through complex aromatic metabolic pathways and used as energy source in the tricarboxylic acid cycle. Over the decades, bacterial aromatic metabolism has been described in great detail. However, the studies on fungal aromatic pathways are scattered over different pathways and species, complicating a comprehensive view of fungal aromatic metabolism. In this review, we depicted the similarities and differences of the reported aromatic metabolic pathways in fungi and bacteria. Although both microorganisms share the main conversion routes, many alternative pathways are observed in fungi. Understanding the microbial aromatic metabolic pathways could lead to metabolic engineering for strain improvement and promote valorization of lignin and related aromatic compounds.
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Affiliation(s)
- Ronnie J M Lubbers
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Adiphol Dilokpimol
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Jaap Visser
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Miia R Mäkelä
- Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
| | - Kristiina S Hildén
- Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
| | - Ronald P de Vries
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands; Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
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Brink DP, Ravi K, Lidén G, Gorwa-Grauslund MF. Mapping the diversity of microbial lignin catabolism: experiences from the eLignin database. Appl Microbiol Biotechnol 2019; 103:3979-4002. [PMID: 30963208 PMCID: PMC6486533 DOI: 10.1007/s00253-019-09692-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 02/06/2019] [Accepted: 02/09/2019] [Indexed: 12/18/2022]
Abstract
Lignin is a heterogeneous aromatic biopolymer and a major constituent of lignocellulosic biomass, such as wood and agricultural residues. Despite the high amount of aromatic carbon present, the severe recalcitrance of the lignin macromolecule makes it difficult to convert into value-added products. In nature, lignin and lignin-derived aromatic compounds are catabolized by a consortia of microbes specialized at breaking down the natural lignin and its constituents. In an attempt to bridge the gap between the fundamental knowledge on microbial lignin catabolism, and the recently emerging field of applied biotechnology for lignin biovalorization, we have developed the eLignin Microbial Database ( www.elignindatabase.com ), an openly available database that indexes data from the lignin bibliome, such as microorganisms, aromatic substrates, and metabolic pathways. In the present contribution, we introduce the eLignin database, use its dataset to map the reported ecological and biochemical diversity of the lignin microbial niches, and discuss the findings.
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Affiliation(s)
- Daniel P Brink
- Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, SE-221 00, Lund, Sweden.
| | - Krithika Ravi
- Department of Chemical Engineering, Lund University, Lund, Sweden
| | - Gunnar Lidén
- Department of Chemical Engineering, Lund University, Lund, Sweden
| | - Marie F Gorwa-Grauslund
- Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, SE-221 00, Lund, Sweden
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16
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Ravi K, Abdelaziz OY, Nöbel M, García-Hidalgo J, Gorwa-Grauslund MF, Hulteberg CP, Lidén G. Bacterial conversion of depolymerized Kraft lignin. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:56. [PMID: 30923564 PMCID: PMC6420747 DOI: 10.1186/s13068-019-1397-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 03/08/2019] [Indexed: 05/24/2023]
Abstract
BACKGROUND Lignin is a potential feedstock for microbial conversion into various chemicals. However, the microbial degradation rate of native or technical lignin is low, and chemical depolymerization is needed to obtain reasonable conversion rates. In the current study, nine bacterial strains belonging to the Pseudomonas and Rhodococcus genera were evaluated for their ability to grow on alkaline-treated softwood lignin as a sole carbon source. RESULTS Pseudomonas fluorescens DSM 50090 and Rhodococcus opacus DSM1069 showed the best growth of the tested species on plates with lignin. Further evaluation of P. fluorescens and R. opacus was made in liquid cultivations with depolymerized softwood Kraft lignin (DL) at a concentration of 1 g/L. Size-exclusion chromatography (SEC) showed that R. opacus consumed most of the available lower-molecular weight compounds (approximately 0.1-0.4 kDa) in the DL, but the weight distribution of larger fractions was almost unaffected. Importantly, the consumed compounds included guaiacol-one of the main monomers in the DL. SEC analysis of P. fluorescens culture broth, in contrast, did not show a large conversion of low-molecular weight compounds, and guaiacol remained unconsumed. However, a significant shift in molecular weight distribution towards lower average weights was seen after cultivation with P. fluorescens. CONCLUSIONS Rhodococcus opacus and P. fluorescens were identified as two potential microbial candidates for the conversion/consumption of base-catalyzed depolymerized lignin, acting on low- and high-molecular weight lignin fragments, respectively. These findings will be of relevance for designing bioconversion of softwood Kraft lignin.
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Affiliation(s)
- Krithika Ravi
- Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | - Omar Y. Abdelaziz
- Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | - Matthias Nöbel
- Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund, Sweden
- Present Address: Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane, QLD 4072 Australia
| | - Javier García-Hidalgo
- Department of Chemistry, Applied Microbiology, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | - Marie F. Gorwa-Grauslund
- Department of Chemistry, Applied Microbiology, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | | | - Gunnar Lidén
- Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund, Sweden
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17
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Xu Z, Lei P, Zhai R, Wen Z, Jin M. Recent advances in lignin valorization with bacterial cultures: microorganisms, metabolic pathways, and bio-products. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:32. [PMID: 30815030 PMCID: PMC6376720 DOI: 10.1186/s13068-019-1376-0] [Citation(s) in RCA: 111] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 02/08/2019] [Indexed: 05/09/2023]
Abstract
Lignin is the most abundant aromatic substrate on Earth and its valorization technologies are still under developed. Depolymerization and fragmentation are the predominant preparatory strategies for valorization of lignin to chemicals and fuels. However, due to the structural heterogeneity of lignin, depolymerization and fragmentation typically result in diverse product species, which require extensive separation and purification procedures to obtain target products. For lignin valorization, bacterial-based systems have attracted increasing attention because of their diverse metabolisms, which can be used to funnel multiple lignin-based compounds into specific target products. Here, recent advances in lignin valorization using bacteria are critically reviewed, including lignin-degrading bacteria that are able to degrade lignin and use lignin-associated aromatics, various associated metabolic pathways, and application of bacterial cultures for lignin valorization. This review will provide insight into the recent breakthroughs and future trends of lignin valorization based on bacterial systems.
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Affiliation(s)
- Zhaoxian Xu
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, 210094 China
| | - Peng Lei
- Nanjing Institute for Comprehensive Utilization of Wild Plants, Nanjing, 211111 China
| | - Rui Zhai
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, 210094 China
| | - Zhiqiang Wen
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, 210094 China
| | - Mingjie Jin
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, 210094 China
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Ravi K, Abdelaziz OY, Nöbel M, García-Hidalgo J, Gorwa-Grauslund MF, Hulteberg CP, Lidén G. Bacterial conversion of depolymerized Kraft lignin. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:240. [PMID: 30202435 PMCID: PMC6123935 DOI: 10.1186/s13068-018-1240-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 08/27/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Lignin is a potential feedstock for microbial conversion into various chemicals. However, the degradation rate of native or technical lignin is low, and depolymerization is needed to obtain reasonable conversion rates. In the current study, base-catalyzed depolymerization-using NaOH (5 wt%)-of softwood Kraft lignin was conducted in a continuous-flow reactor system at temperatures in the range 190-240 °C and residence times of 1 or 2 min. The ability of growth of nine bacterial strains belonging to the genera Pseudomonas and Rhodococcus was tested using the alkaline-treated lignin as a sole carbon source. RESULTS Pseudomonas fluorescens and Rhodococcus opacus showed the best growth of the tested species on plates with lignin. Further evaluation of P. fluorescens and R. opacus was made in liquid cultivations with depolymerized lignin (DL) at a concentration of 1 g/L. Size exclusion chromatography (SEC) showed that R. opacus consumed most of the available lower molecular weight compounds (approximately 0.1-0.4 kDa) in the DL, but the weight distribution of larger fractions was almost unaffected. Importantly, the consumed compounds included guaiacol-one of the main monomers in the DL. SEC analysis of P. fluorescens culture broth, in contrast, did not show a large conversion of low molecular weight compounds, and guaiacol remained unconsumed. However, a significant shift in molecular weight distribution towards lower average weights was seen. CONCLUSIONS Rhodococcus opacus and P. fluorescens were identified as two potential microbial candidates for the conversion/consumption of base-catalyzed depolymerized lignin, acting on low and high molecular weight lignin fragments, respectively. These findings will be of relevance for designing bioconversion of softwood Kraft lignin.
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Affiliation(s)
- Krithika Ravi
- Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | - Omar Y. Abdelaziz
- Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | - Matthias Nöbel
- Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund, Sweden
- Present Address: Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane, QLD 4072 Australia
| | - Javier García-Hidalgo
- Department of Chemistry, Applied Microbiology, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | - Marie F. Gorwa-Grauslund
- Department of Chemistry, Applied Microbiology, Lund University, P.O. Box 124, 221 00 Lund, Sweden
| | | | - Gunnar Lidén
- Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund, Sweden
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Alternatives for Chemical and Biochemical Lignin Valorization: Hot Topics from a Bibliometric Analysis of the Research Published During the 2000–2016 Period. Processes (Basel) 2018. [DOI: 10.3390/pr6080098] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A complete bibliometric analysis of the Scopus database was performed to identify the research trends related to lignin valorization from 2000 to 2016. The results from this analysis revealed an exponentially increasing number of publications and a high relevance of interdisciplinary collaboration. The simultaneous valorization of the three main components of lignocellulosic biomass (cellulose, hemicellulose, and lignin) has been revealed as a key aspect and optimal pretreatment is required for the subsequent lignin valorization. Research covers the determination of the lignin structure, isolation, and characterization; depolymerization by thermal and thermochemical methods; chemical, biochemical and biological conversion of depolymerized lignin; and lignin applications. Most methods for lignin depolymerization are focused on the selective cleavage of the β-O-4 linkage. Although many depolymerization methods have been developed, depolymerization with sodium hydroxide is the dominant process at industrial scale. Oxidative conversion of lignin is the most used method for the chemical lignin upgrading. Lignin uses can be classified according to its structure into lignin-derived aromatic compounds, lignin-derived carbon materials and lignin-derived polymeric materials. There are many advances in all approaches, but lignin-derived polymeric materials appear as a promising option.
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