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Bing RG, Ford KC, Willard DJ, Manesh MJH, Straub CT, Laemthong T, Alexander BH, Tanwee T, O'Quinn HC, Poole FL, Vailionis J, Zhang Y, Rodionov D, Adams MWW, Kelly RM. Engineering ethanologenicity into the extremely thermophilic bacterium Anaerocellum (f. Caldicellulosiriuptor) bescii. Metab Eng 2024; 86:99-114. [PMID: 39305946 DOI: 10.1016/j.ymben.2024.09.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2024] [Revised: 08/19/2024] [Accepted: 09/15/2024] [Indexed: 09/27/2024]
Abstract
The anaerobic bacterium Anaerocellum (f. Caldicellulosiruptor) bescii natively ferments the carbohydrate content of plant biomass (including microcrystalline cellulose) into predominantly acetate, H2, and CO2, and smaller amounts of lactate, alanine and valine. While this extreme thermophile (growth Topt 78 °C) is not natively ethanologenic, it has been previously metabolically engineered with this property, albeit initially yielding low solvent titers (∼15 mM). Herein we report significant progress on improving ethanologenicity in A. bescii, such that titers above 130 mM have now been achieved, while concomitantly improving selectivity by minimizing acetate formation. Metabolic engineering progress has benefited from improved molecular genetic tools and better understanding of A. bescii growth physiology. Heterologous expression of a mutated thermophilic alcohol dehydrogenase (AdhE) modified for co-factor requirement, coupled with bioreactor operation strategies related to pH control, have been key to enhanced ethanol generation and fermentation product specificity. Insights gained from metabolic modeling of A. bescii set the stage for its further improvement as a metabolic engineering platform.
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Affiliation(s)
- Ryan G Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Kathryne C Ford
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Daniel J Willard
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Mohamad J H Manesh
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Christopher T Straub
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Tunyaboon Laemthong
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Benjamin H Alexander
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Tania Tanwee
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Hailey C O'Quinn
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Farris L Poole
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Jason Vailionis
- Department of Cell and Molecular Biology, College of the Environment and Life Sciences, University of Rhode Island, Kingston, RI, USA
| | - Ying Zhang
- Department of Cell and Molecular Biology, College of the Environment and Life Sciences, University of Rhode Island, Kingston, RI, USA
| | - Dmitry Rodionov
- Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA.
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2
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Sitara A, Hocq R, Horvath J, Pflügl S. Industrial biotechnology goes thermophilic: Thermoanaerobes as promising hosts in the circular carbon economy. BIORESOURCE TECHNOLOGY 2024; 408:131164. [PMID: 39069138 DOI: 10.1016/j.biortech.2024.131164] [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: 05/27/2024] [Revised: 07/19/2024] [Accepted: 07/24/2024] [Indexed: 07/30/2024]
Abstract
Transitioning away from fossil feedstocks is imperative to mitigate climate change, and necessitates the utilization of renewable, alternative carbon and energy sources to foster a circular carbon economy. In this context, lignocellulosic biomass and one-carbon compounds emerge as promising feedstocks that could be renewably upgraded by thermophilic anaerobes (thermoanaerobes) via gas fermentation or consolidated bioprocessing to value-added products. In this review, the potential of thermoanaerobes for cost-efficient, effective and sustainable bioproduction is discussed. Metabolic and bioprocess engineering approaches are reviewed to draw a comprehensive picture of current developments and future perspectives for the conversion of renewable feedstocks to chemicals and fuels of interest. Selected bioprocessing scenarios are outlined, offering practical insights into the applicability of thermoanaerobes at a large scale. Collectively, the potential advantages of thermoanaerobes regarding process economics could facilitate an easier transition towards sustainable bioprocesses with renewable feedstocks.
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Affiliation(s)
- Angeliki Sitara
- Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
| | - Rémi Hocq
- Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria; Christian Doppler Laboratory for Optimized Expression of Carbohydrate-active Enzymes, Institute of Chemical, Environmental and Bioscience Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria; CIRCE Biotechnologie GmbH, Kerpengasse 125, 1210 Vienna, Austria
| | - Josef Horvath
- Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria; Christian Doppler Laboratory for Optimized Expression of Carbohydrate-active Enzymes, Institute of Chemical, Environmental and Bioscience Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
| | - Stefan Pflügl
- Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria; Christian Doppler Laboratory for Optimized Expression of Carbohydrate-active Enzymes, Institute of Chemical, Environmental and Bioscience Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria.
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Bing RG, Willard DJ, Crosby JR, Adams MWW, Kelly RM. Whither the genus Caldicellulosiruptor and the order Thermoanaerobacterales: phylogeny, taxonomy, ecology, and phenotype. Front Microbiol 2023; 14:1212538. [PMID: 37601363 PMCID: PMC10434631 DOI: 10.3389/fmicb.2023.1212538] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 07/20/2023] [Indexed: 08/22/2023] Open
Abstract
The order Thermoanaerobacterales currently consists of fermentative anaerobic bacteria, including the genus Caldicellulosiruptor. Caldicellulosiruptor are represented by thirteen species; all, but one, have closed genome sequences. Interest in these extreme thermophiles has been motivated not only by their high optimal growth temperatures (≥70°C), but also by their ability to hydrolyze polysaccharides including, for some species, both xylan and microcrystalline cellulose. Caldicellulosiruptor species have been isolated from geographically diverse thermal terrestrial environments located in New Zealand, China, Russia, Iceland and North America. Evidence of their presence in other terrestrial locations is apparent from metagenomic signatures, including volcanic ash in permafrost. Here, phylogeny and taxonomy of the genus Caldicellulosiruptor was re-examined in light of new genome sequences. Based on genome analysis of 15 strains, a new order, Caldicellulosiruptorales, is proposed containing the family Caldicellulosiruptoraceae, consisting of two genera, Caldicellulosiruptor and Anaerocellum. Furthermore, the order Thermoanaerobacterales also was re-assessed, using 91 genome-sequenced strains, and should now include the family Thermoanaerobacteraceae containing the genera Thermoanaerobacter, Thermoanaerobacterium, Caldanaerobacter, the family Caldanaerobiaceae containing the genus Caldanaerobius, and the family Calorimonaceae containing the genus Calorimonas. A main outcome of ANI/AAI analysis indicates the need to reclassify several previously designated species in the Thermoanaerobacterales and Caldicellulosiruptorales by condensing them into strains of single species. Comparative genomics of carbohydrate-active enzyme inventories suggested differentiating phenotypic features, even among strains of the same species, reflecting available nutrients and ecological roles in their native biotopes.
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Affiliation(s)
- Ryan G. Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States
| | - Daniel J. Willard
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States
| | - James R. Crosby
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States
| | - Michael W. W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States
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Laemthong T, Bing RG, Crosby JR, Manesh MJH, Adams MWW, Kelly RM. Role of cell-substrate association during plant biomass solubilization by the extreme thermophile Caldicellulosiruptor bescii. Extremophiles 2023; 27:6. [PMID: 36802247 PMCID: PMC10514702 DOI: 10.1007/s00792-023-01290-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 02/02/2023] [Indexed: 02/23/2023]
Abstract
Caldicellulosiruptor species are proficient at solubilizing carbohydrates in lignocellulosic biomass through surface (S)-layer bound and secretomic glycoside hydrolases. Tāpirins, surface-associated, non-catalytic binding proteins in Caldicellulosiruptor species, bind tightly to microcrystalline cellulose, and likely play a key role in natural environments for scavenging scarce carbohydrates in hot springs. However, the question arises: If tāpirin concentration on Caldicellulosiruptor cell walls increased above native levels, would this offer any benefit to lignocellulose carbohydrate hydrolysis and, hence, biomass solubilization? This question was addressed by engineering the genes for tight-binding, non-native tāpirins into C. bescii. The engineered C. bescii strains bound more tightly to microcrystalline cellulose (Avicel) and biomass compared to the parent. However, tāpirin overexpression did not significantly improve solubilization or conversion for wheat straw or sugarcane bagasse. When incubated with poplar, the tāpirin-engineered strains increased solubilization by 10% compared to the parent, and corresponding acetate production, a measure of carbohydrate fermentation intensity, was 28% higher for the Calkr_0826 expression strain and 18.5% higher for the Calhy_0908 expression strain. These results show that enhanced binding to the substrate, beyond the native capability, did not improve C. bescii solubilization of plant biomass, but in some cases may improve conversion of released lignocellulose carbohydrates to fermentation products.
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Affiliation(s)
- Tunyaboon Laemthong
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695-7905, USA
- Department of Chemical Engineering, Thammasat University, Pathum Thani, 12120, Thailand
| | - Ryan G Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695-7905, USA
| | - James R Crosby
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695-7905, USA
| | - Mohamad J H Manesh
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695-7905, USA
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27695-7905, USA.
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Bing RG, Carey MJ, Laemthong T, Willard DJ, Crosby JR, Sulis DB, Wang JP, Adams MWW, Kelly RM. Fermentative conversion of unpretreated plant biomass: A thermophilic threshold for indigenous microbial growth. BIORESOURCE TECHNOLOGY 2023; 367:128275. [PMID: 36347479 PMCID: PMC10561188 DOI: 10.1016/j.biortech.2022.128275] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/31/2022] [Accepted: 11/01/2022] [Indexed: 06/16/2023]
Abstract
Naturally occurring, microbial contaminants were found in plant biomasses from common bioenergy crops and agricultural wastes. Unexpectedly, indigenous thermophilic microbes were abundant, raising the question of whether they impact thermophilic consolidated bioprocessing fermentations that convert biomass directly into useful bioproducts. Candidate microbial platforms for biomass conversion, Acetivibrio thermocellus (basionym Clostridium thermocellum; Topt 60 °C) and Caldicellulosiruptor bescii (Topt 78 °C), each degraded a wide variety of plant biomasses, but only A. thermocellus was significantly affected by the presence of indigenous microbial populations harbored by the biomass. Indigenous microbial growth was eliminated at ≥75 °C, conditions where C. bescii thrives, but where A. thermocellus cannot survive. Therefore, 75 °C is the thermophilic threshold to avoid sterilizing pre-treatments on the biomass that prevents native microbes from competing with engineered microbes and forming undesirable by-products. Thermophiles that naturally grow at and above 75 °C offer specific advantages as platform microorganisms for biomass conversion into fuels and chemicals.
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Affiliation(s)
- Ryan G Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Morgan J Carey
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Tunyaboon Laemthong
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Daniel J Willard
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - James R Crosby
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States
| | - Daniel B Sulis
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695, United States
| | - Jack P Wang
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695, United States
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, United States
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, United States.
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Wang J, Wei J, Li H, Li Y. High-efficiency genome editing of an extreme thermophile Thermus thermophilus using endogenous type I and type III CRISPR-Cas systems. MLIFE 2022; 1:412-427. [PMID: 38818488 PMCID: PMC10989782 DOI: 10.1002/mlf2.12045] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 10/13/2022] [Accepted: 10/15/2022] [Indexed: 06/01/2024]
Abstract
Thermus thermophilus is an attractive species in the bioindustry due to its valuable natural products, abundant thermophilic enzymes, and promising fermentation capacities. However, efficient and versatile genome editing tools are not available for this species. In this study, we developed an efficient genome editing tool for T. thermophilus HB27 based on its endogenous type I-B, I-C, and III-A/B CRISPR-Cas systems. First, we systematically characterized the DNA interference capabilities of the different types of the native CRISPR-Cas systems in T. thermophilus HB27. We found that genomic manipulations such as gene deletion, mutation, and in situ tagging could be easily implemented by a series of genome-editing plasmids carrying an artificial self-targeting mini-CRISPR and a donor DNA responsible for the recombinant recovery. We also compared the genome editing efficiency of different CRISPR-Cas systems and the editing plasmids with donor DNAs of different lengths. Additionally, we developed a reporter gene system for T. thermophilus based on a heat-stable β-galactosidase gene TTP0042, and constructed an engineered strain with a high production capacity of superoxide dismutases by genome modification.
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Affiliation(s)
- Jinting Wang
- State Key Laboratory of Agricultural Microbiology and College of Life Science and TechnologyHuazhong Agricultural UniversityWuhanChina
- Shenzhen Institute of Nutrition and HealthHuazhong Agricultural UniversityShenzhenChina
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at ShenzhenChinese Academy of Agricultural SciencesShenzhenChina
| | - Junwei Wei
- State Key Laboratory of Agricultural Microbiology and College of Life Science and TechnologyHuazhong Agricultural UniversityWuhanChina
- Shenzhen Institute of Nutrition and HealthHuazhong Agricultural UniversityShenzhenChina
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at ShenzhenChinese Academy of Agricultural SciencesShenzhenChina
| | - Haijuan Li
- College of Biological and Environmental EngineeringXi'an UniversityXi'anChina
| | - Yingjun Li
- State Key Laboratory of Agricultural Microbiology and College of Life Science and TechnologyHuazhong Agricultural UniversityWuhanChina
- Shenzhen Institute of Nutrition and HealthHuazhong Agricultural UniversityShenzhenChina
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at ShenzhenChinese Academy of Agricultural SciencesShenzhenChina
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Laemthong T, Bing RG, Crosby JR, Adams MWW, Kelly RM. Engineering Caldicellulosiruptor bescii with Surface Layer Homology Domain-Linked Glycoside Hydrolases Improves Plant Biomass Solubilization. Appl Environ Microbiol 2022; 88:e0127422. [PMID: 36169328 PMCID: PMC9599439 DOI: 10.1128/aem.01274-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 09/12/2022] [Indexed: 11/20/2022] Open
Abstract
Extremely thermophilic Caldicellulosiruptor species solubilize carbohydrates from lignocellulose through glycoside hydrolases (GHs) that can be extracellular, intracellular, or cell surface layer (S-layer) associated. Caldicellulosiruptor genomes sequenced so far encode at least one surface layer homology domain glycoside hydrolase (SLH-GH), representing six different classes of these enzymes; these can have multiple binding and catalytic domains. Biochemical characterization of a representative from each class was done to determine their biocatalytic features: four SLH-GHs from Caldicellulosiruptor kronotskyensis (Calkro_0111, Calkro_0402, Calkro_0072, and Calkro_2036) and two from Caldicellulosiruptor hydrothermalis (Calhy_1629 and Calhy_2383). Calkro_0111, Calkro_0072, and Calhy_2383 exhibited β-1,3-glucanase activity, Calkro_0402 was active on both β-1,3/1,4-glucan and β-1,4-xylan, Calkro_2036 exhibited activity on both β-1,3/1,4-glucan and β-1,4-glucan, and Calhy_1629 was active only on arabinan. Caldicellulosiruptor bescii, the only species with molecular genetic tools as well as already a strong cellulose degrader, contains only one SLH-GH, Athe_0594, a glucanase that is a homolog of Calkro_2036; the other 5 classes of SLH-GHs are absent in C. bescii. The C. bescii secretome, supplemented with individual enzymes or cocktails of SLH-GHs, increased in vitro sugar release from sugar cane bagasse and poplar. Expression of non-native SLH-GHs in vivo, either associated with the S-layer or as freely secreted enzymes, improved total carbohydrate solubilization of sugar cane bagasse and poplar by up to 45% and 23%, respectively. Most notably, expression of Calkro_0402, a xylanase/glucanase, improved xylose solubilization from poplar and bagasse by over 70% by C. bescii. While Caldicellulosiruptor species are already prolific lignocellulose degraders, they can be further improved by the strategy described here. IMPORTANCE Caldicellulosiruptor species hold promise as microorganisms that can solubilize the carbohydrate portion of lignocellulose and subsequently convert fermentable sugars into bio-based chemicals and fuels. Members of the genus have surface layer (S-layer) homology domain-associated glycoside hydrolases (SLH-GHs) that mediate attachment to biomass as well as hydrolysis of carbohydrates. Caldicellulosiruptor bescii, the most studied member of the genus, has only one SLH-GH. Expression of SLH-GHs from other Caldicellulosiruptor species in C. bescii significantly improved degradation of sugar cane bagasse and poplar. This suggests that this extremely thermophilic bacterium can be engineered to further improve its ability to degrade specific plant biomasses by inserting genes encoding SLH-GHs recruited from other Caldicellulosiruptor species.
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Affiliation(s)
- Tunyaboon Laemthong
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Ryan G. Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - James R. Crosby
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Michael W. W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
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Adeniyi A, Bello I, Mukaila T, Hammed A. A Review of Microbial Molecular Profiling during Biomass Valorization. BIOTECHNOL BIOPROC E 2022. [DOI: 10.1007/s12257-022-0026-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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