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Ashoor S, Mathew GM, Sukumaran RK. Rice straw hydrolysis using in-situ produced enzymes: Feedstock influences fungal enzyme composition and hydrolytic efficiency. Prep Biochem Biotechnol 2024; 54:967-973. [PMID: 38327105 DOI: 10.1080/10826068.2024.2312458] [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] [Indexed: 02/09/2024]
Abstract
Trichoderma reesei RUT-C30 was cultivated on differentially pretreated rice straw and pure cellulose as a carbon source/inducer for cellulase production, and the enzymes were evaluated for hydrolysis of sequential acid and alkali pretreated rice straw. Growth on pretreated rice straw enhanced protein secretion and cellulase activities compared to pure cellulose as a carbon source. The yield of cellulolytic enzymes was higher for alkali pretreated rice straw (ALP-RS), while H2O2-treated (HP-RS) could not induce cellulases to a larger level compared to pure cellulose. Protein concentration was 3.5-fold higher on ALP-RS as compared to pure cellulose, with a maximum filter-paper cellulase (FPase) activity of 1.76 IU/ml and carboxy-methyl cellulase (CMCase) activity of 40.16 IU/ml (2.18 fold higher). Beta-glucosidase (BGL) activity was more or less the same with the different substrates and supplementation of heterologous BGL could result in a quantum jump in hydrolytic efficiencies, which in the case of ALP-RS induced enzymes was 34% (increased from 69.26% to 92.51%). The use of lignocellulosic biomass (LCB) itself as a substrate for the production of cellulase is advantageous not only in terms of raw material costs but also for obtaining a more suitable enzyme profile for biomass hydrolysis.
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Affiliation(s)
- Selim Ashoor
- Department of Agricultural Microbiology, Faculty of Agriculture, Ain Shams University, Cairo, Egypt
| | - Gincy Marina Mathew
- Biofuels and Biorefineries Section, Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Thiruvananthapuram, India
| | - Rajeev K Sukumaran
- Biofuels and Biorefineries Section, Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Thiruvananthapuram, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India
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2
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Moraïs S, Stern J, Artzi L, Fontes CMGA, Bayer EA, Mizrahi I. Carbohydrate Depolymerization by Intricate Cellulosomal Systems. Methods Mol Biol 2023; 2657:53-77. [PMID: 37149522 DOI: 10.1007/978-1-0716-3151-5_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Cellulosomes are multi-enzymatic nanomachines that have been fine-tuned through evolution to efficiently deconstruct plant biomass. Integration of cellulosomal components occurs via highly ordered protein-protein interactions between the various enzyme-borne dockerin modules and the multiple copies of the cohesin modules located on the scaffoldin subunit. Recently, designer cellulosome technology was established to provide insights into the architectural role of catalytic (enzymatic) and structural (scaffoldin) cellulosomal constituents for the efficient degradation of plant cell wall polysaccharides. Owing to advances in genomics and proteomics, highly structured cellulosome complexes have recently been unraveled, and the information gained has inspired the development of designer-cellulosome technology to new levels of complex organization. These higher-order designer cellulosomes have in turn fostered our capacity to enhance the catalytic potential of artificial cellulolytic complexes. In this chapter, methods to produce and employ such intricate cellulosomal complexes are reported.
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Affiliation(s)
- Sarah Moraïs
- Faculty of Natural Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Johanna Stern
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Lior Artzi
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | | | - Edward A Bayer
- Faculty of Natural Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel.
| | - Itzhak Mizrahi
- Faculty of Natural Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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3
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Dorival J, Moraïs S, Labourel A, Rozycki B, Cazade PA, Dabin J, Setter-Lamed E, Mizrahi I, Thompson D, Thureau A, Bayer EA, Czjzek M. Mapping the deformability of natural and designed cellulosomes in solution. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2022; 15:68. [PMID: 35725490 PMCID: PMC9210761 DOI: 10.1186/s13068-022-02165-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 06/08/2022] [Indexed: 12/02/2022]
Abstract
BACKGROUND Natural cellulosome multi-enzyme complexes, their components, and engineered 'designer cellulosomes' (DCs) promise an efficient means of breaking down cellulosic substrates into valuable biofuel products. Their broad uptake in biotechnology relies on boosting proximity-based synergy among the resident enzymes, but the modular architecture challenges structure determination and rational design. RESULTS We used small angle X-ray scattering combined with molecular modeling to study the solution structure of cellulosomal components. These include three dockerin-bearing cellulases with distinct substrate specificities, original scaffoldins from the human gut bacterium Ruminococcus champanellensis (ScaA, ScaH and ScaK) and a trivalent cohesin-bearing designer scaffoldin (Scaf20L), followed by cellulosomal complexes comprising these components, and the nonavalent fully loaded Clostridium thermocellum CipA in complex with Cel8A from the same bacterium. The size analysis of Rg and Dmax values deduced from the scattering curves and corresponding molecular models highlight their variable aspects, depending on composition, size and spatial organization of the objects in solution. CONCLUSIONS Our data quantifies variability of form and compactness of cellulosomal components in solution and confirms that this native plasticity may well be related to speciation with respect to the substrate that is targeted. By showing that scaffoldins or components display enhanced compactness compared to the free objects, we provide new routes to rationally enhance their stability and performance in their environment of action.
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Affiliation(s)
- Jonathan Dorival
- Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), Sorbonne Université, CNRS, 29680, Roscoff, Bretagne, France
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, 37232, USA
| | - Sarah Moraïs
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 7610001, Rehovot, Israel
- Faculty of Natural Sciences, Ben-Gurion University of the Negev, 8499000, Beer-Sheva, Israel
| | - Aurore Labourel
- TBI, Université de Toulouse, CNRS, INRAE, INSA, Toulouse, France
| | - Bartosz Rozycki
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668, Warsaw, Poland
| | - Pierre-Andre Cazade
- Department of Physics, Bernal Institute, University of Limerick, Limerick, Ireland
| | - Jérôme Dabin
- Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), Sorbonne Université, CNRS, 29680, Roscoff, Bretagne, France
| | - Eva Setter-Lamed
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 7610001, Rehovot, Israel
| | - Itzhak Mizrahi
- Faculty of Natural Sciences, Ben-Gurion University of the Negev, 8499000, Beer-Sheva, Israel
| | - Damien Thompson
- Department of Physics, Bernal Institute, University of Limerick, Limerick, Ireland
| | | | - Edward A Bayer
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 7610001, Rehovot, Israel
- Faculty of Natural Sciences, Ben-Gurion University of the Negev, 8499000, Beer-Sheva, Israel
| | - Mirjam Czjzek
- Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), Sorbonne Université, CNRS, 29680, Roscoff, Bretagne, France.
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Galera-Prat A, Vera AM, Moraïs S, Vazana Y, Bayer EA, Carrión-Vázquez M. Impact of scaffoldin mechanostability on cellulosomal activity. Biomater Sci 2020; 8:3601-3610. [PMID: 32232253 DOI: 10.1039/c9bm02052g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lignocellulose is the most abundant renewable carbon source in the biosphere. However, the main bottleneck in its conversion to produce second generation biofuels is the saccharification step: the hydrolysis of lignocellulosic material into soluble fermentable sugars. Some anaerobic bacteria have developed an extracellular multi-enzyme complex called the cellulosome that efficiently degrades cellulosic substrates. Cellulosome complexes rely on enzyme-integrating scaffoldins that are large non-catalytic scaffolding proteins comprising several cohesin modules and additional functional modules that mediate the anchoring of the complex to the cell surface and the specific binding to its cellulosic substrate. It was proposed that mechanical forces may affect the cohesins positioned between the cell- and cellulose-anchoring points in the so-called connecting region. Consequently, the mechanical resistance of cohesins within the scaffoldin is of great importance, both to understand cellulosome function and as a parameter of industrial interest, to better mimic natural complexes through the use of the established designer cellulosome technology. Here we study how the mechanical stability of cohesins in a scaffoldin affects the enzymatic activity of a cellulosome. We found that when a cohesin of low mechanical stability is positioned in the connecting region of a scaffoldin, the activity of the resulting cellulosome is reduced as opposed to a cohesin of higher mechanical stability. This observation directly relates mechanical stability of the scaffoldin-borne cohesins to cellulosome activity and provides a rationale for the design of artificial cellulosomes for industrial applications, by incorporating mechanical stability as a new industrial parameter in the biotechnology toolbox.
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Affiliation(s)
- Albert Galera-Prat
- Instituto Cajal, Department of Molecular, Cellular and Developmental Neurobiology. IC-CSIC, Avenida Doctor Arce 37, 28002 Madrid, Spain.
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Levi Hevroni B, Moraïs S, Ben-David Y, Morag E, Bayer EA. Minimalistic Cellulosome of the Butanologenic Bacterium Clostridium saccharoperbutylacetonicum. mBio 2020; 11:e00443-20. [PMID: 32234813 PMCID: PMC7157769 DOI: 10.1128/mbio.00443-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 03/05/2020] [Indexed: 12/31/2022] Open
Abstract
Clostridium saccharoperbutylacetonicum is a mesophilic, anaerobic, butanol-producing bacterium, originally isolated from soil. It was recently reported that C. saccharoperbutylacetonicum possesses multiple cellulosomal elements and would potentially form the smallest cellulosome known in nature. Its genome contains only eight dockerin-bearing enzymes, and its unique scaffoldin bears two cohesins (Cohs), three X2 modules, and two carbohydrate-binding modules (CBMs). In this study, all of the cellulosome-related modules were cloned, expressed, and purified. The recombinant cohesins, dockerins, and CBMs were tested for binding activity using enzyme-linked immunosorbent assay (ELISA)-based techniques. All the enzymes were tested for their comparative enzymatic activity on seven different cellulosic and hemicellulosic substrates, thus revealing four cellulases, a xylanase, a mannanase, a xyloglucanase, and a lichenase. All dockerin-containing enzymes interacted similarly with the second cohesin (Coh2) module, whereas Coh1 was more restricted in its interaction pattern. In addition, the polysaccharide-binding properties of the CBMs within the scaffoldin were examined by two complementary assays, affinity electrophoresis and affinity pulldown. The scaffoldin of C. saccharoperbutylacetonicum exhibited high affinity for cellulosic and hemicellulosic substrates, specifically to microcrystalline cellulose and xyloglucan. Evidence that supports substrate-dependent in vivo secretion of cellulosomes is presented. The results of our analyses contribute to a better understanding of simple cellulosome systems by identifying the key players in this minimalistic system and the binding pattern of its cohesin-dockerin interaction. The knowledge gained by our study will assist further exploration of similar minimalistic cellulosomes and will contribute to the significance of specific sets of defined cellulosomal enzymes in the degradation of cellulosic biomass.IMPORTANCE Cellulosome-producing bacteria are considered among the most important bacteria in both mesophilic and thermophilic environments, owing to their capacity to deconstruct recalcitrant plant-derived polysaccharides (and notably cellulose) into soluble saccharides for subsequent processing. In many ecosystems, the cellulosome-producing bacteria are particularly effective "first responders." The massive amounts of sugars produced are potentially amenable in industrial settings to further fermentation by appropriate microbes to biofuels, notably ethanol and butanol. Among the solvent-producing bacteria, Clostridium saccharoperbutylacetonicum has the smallest cellulosome system known thus far. The importance of investigating the building blocks of such a small, multifunctional nanomachine is crucial to understanding the fundamental activities of this efficient enzymatic complex.
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Affiliation(s)
- Bosmat Levi Hevroni
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Sarah Moraïs
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Yonit Ben-David
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Ely Morag
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Edward A Bayer
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
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6
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Kahn A, Moraïs S, Chung D, Sarai NS, Hengge NN, Kahn A, Himmel ME, Bayer EA, Bomble YJ. Glycosylation of hyperthermostable designer cellulosome components yields enhanced stability and cellulose hydrolysis. FEBS J 2020; 287:4370-4388. [DOI: 10.1111/febs.15251] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 01/06/2020] [Accepted: 02/14/2020] [Indexed: 12/17/2022]
Affiliation(s)
- Amaranta Kahn
- Department of Biomolecular Sciences The Weizmann Institute of Science Rehovot Israel
| | - Sarah Moraïs
- Department of Biomolecular Sciences The Weizmann Institute of Science Rehovot Israel
- Faculty of Natural Sciences Ben‐Gurion University of the Negev Beer‐Sheva Israel
| | - Daehwan Chung
- Biosciences Center National Renewable Energy Laboratory Golden CO USA
| | - Nicholas S. Sarai
- Biosciences Center National Renewable Energy Laboratory Golden CO USA
| | - Neal N. Hengge
- Biosciences Center National Renewable Energy Laboratory Golden CO USA
| | - Audrey Kahn
- Department of Biomolecular Sciences The Weizmann Institute of Science Rehovot Israel
| | - Michael E. Himmel
- Biosciences Center National Renewable Energy Laboratory Golden CO USA
| | - Edward A. Bayer
- Department of Biomolecular Sciences The Weizmann Institute of Science Rehovot Israel
| | - Yannick J. Bomble
- Biosciences Center National Renewable Energy Laboratory Golden CO USA
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7
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Barruetabeña N, Alonso-Lerma B, Galera-Prat A, Joudeh N, Barandiaran L, Aldazabal L, Arbulu M, Alcalde M, De Sancho D, Gavira JA, Carrion-Vazquez M, Perez-Jimenez R. Resurrection of efficient Precambrian endoglucanases for lignocellulosic biomass hydrolysis. Commun Chem 2019. [DOI: 10.1038/s42004-019-0176-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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8
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Kahn A, Moraïs S, Galanopoulou AP, Chung D, Sarai NS, Hengge N, Hatzinikolaou DG, Himmel ME, Bomble YJ, Bayer EA. Creation of a functional hyperthermostable designer cellulosome. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:44. [PMID: 30858881 PMCID: PMC6394049 DOI: 10.1186/s13068-019-1386-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 02/20/2019] [Indexed: 05/28/2023]
Abstract
BACKGROUND Renewable energy has become a field of high interest over the past decade, and production of biofuels from cellulosic substrates has a particularly high potential as an alternative source of energy. Industrial deconstruction of biomass, however, is an onerous, exothermic process, the cost of which could be decreased significantly by use of hyperthermophilic enzymes. An efficient way of breaking down cellulosic substrates can also be achieved by highly efficient enzymatic complexes called cellulosomes. The modular architecture of these multi-enzyme complexes results in substrate targeting and proximity-based synergy among the resident enzymes. However, cellulosomes have not been observed in hyperthermophilic bacteria. RESULTS Here, we report the design and function of a novel hyperthermostable "designer cellulosome" system, which is stable and active at 75 °C. Enzymes from Caldicellulosiruptor bescii, a highly cellulolytic hyperthermophilic anaerobic bacterium, were selected and successfully converted to the cellulosomal mode by grafting onto them divergent dockerin modules that can be inserted in a precise manner into a thermostable chimaeric scaffoldin by virtue of their matching cohesins. Three pairs of cohesins and dockerins, selected from thermophilic microbes, were examined for their stability at extreme temperatures and were determined stable at 75 °C for at least 72 h. The resultant hyperthermostable cellulosome complex exhibited the highest levels of enzymatic activity on microcrystalline cellulose at 75 °C, compared to those of previously reported designer cellulosome systems and the native cellulosome from Clostridium thermocellum. CONCLUSION The functional hyperthermophilic platform fulfills the appropriate physico-chemical properties required for exothermic processes. This system can thus be adapted for other types of thermostable enzyme systems and could serve as a basis for a variety of cellulolytic and non-cellulolytic industrial objectives at high temperatures.
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Affiliation(s)
- Amaranta Kahn
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Sarah Moraïs
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 7610001 Rehovot, Israel
- Faculty of Natural Sciences, Ben-Gurion University of the Negev, 8499000 Beer-Sheva, Israel
| | - Anastasia P. Galanopoulou
- Microbiology Group, Faculty of Biology, National and Kapodistrian University of Athens, Zografou Campus, 15784 Athens, Greece
| | - Daehwan Chung
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO USA
| | - Nicholas S. Sarai
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO USA
- Present Address: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125 USA
| | - Neal Hengge
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO USA
| | - Dimitris G. Hatzinikolaou
- Microbiology Group, Faculty of Biology, National and Kapodistrian University of Athens, Zografou Campus, 15784 Athens, Greece
| | - Michael E. Himmel
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO USA
| | - Yannick J. Bomble
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO USA
| | - Edward A. Bayer
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 7610001 Rehovot, Israel
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9
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Abstract
Enzymatic breakdown of plant biomass is an essential step for its utilization in biorefinery applications, and the products could serve as substrates for the sustainable and environmentally friendly production of fuels and chemicals. Toward this end, the incorporation of enzymes into polyenzymatic cellulosome complexes-able to specifically bind to and hydrolyze crystalline cellulosic materials, such as plant biomass-is known to increase the efficiency and the overall hydrolysis performance of a cellulase system. Despite their relative abundance in various mesophilic anaerobic cellulolytic bacteria, there are only a few reports of cellulosomes of thermophilic origin. However, since various biorefinery processes are favored by elevated temperatures, the development of thermophilic designer cellulosomes could be of great importance. Owing to the limited number of thermophilic cellulosomes, designer cellulosomes, composed of mixtures of mesophilic and thermophilic components, have been constructed. As a result, the overall thermal profile of the individual parts and the resulting complex has to be extensively evaluated. Here, we describe a practical guide for the determination of temperature stability for cellulases in the cellulosome complexes. The approach is also appropriate for other related enzymes, notably xylanases as well as other glycoside hydrolases. We provide detailed experimental procedures for the evaluation of the thermal stability of the individual designer cellulosome components and their complexes as well as protocols for the assessment of complex integrity at elevated temperatures.
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10
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Tabañag IDF, Chu IM, Wei YH, Tsai SL. Ethanol production from hemicellulose by a consortium of different genetically-modified sacharomyces cerevisiae. J Taiwan Inst Chem Eng 2018. [DOI: 10.1016/j.jtice.2018.04.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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11
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Orłowski A, Artzi L, Cazade PA, Gunnoo M, Bayer EA, Thompson D. On the distinct binding modes of expansin and carbohydrate-binding module proteins on crystalline and nanofibrous cellulose: implications for cellulose degradation by designer cellulosomes. Phys Chem Chem Phys 2018. [DOI: 10.1039/c7cp07764e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Transformation of cellulose into monosaccharides can be achieved by hydrolysis of the cellulose chains, carried out by a special group of enzymes known as cellulases.
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Affiliation(s)
- Adam Orłowski
- Department of Physics
- Bernal Institute
- University of Limerick
- Ireland
| | - Lior Artzi
- Department of Biomolecular Sciences
- The Weizmann Institute of Science
- Rehovot
- Israel
| | | | | | - Edward A. Bayer
- Department of Biomolecular Sciences
- The Weizmann Institute of Science
- Rehovot
- Israel
| | - Damien Thompson
- Department of Physics
- Bernal Institute
- University of Limerick
- Ireland
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12
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Abstract
Cellulose deconstruction is achieved in nature through two main enzymatic paradigms, i.e., free enzymes and enzymatic complexes (called cellulosomes). Gaining insights into the mechanism of action and synergy among the different cellulases is of high interest, notably in the field of renewable energy, and specifically, for the conversion of cellulosic biomass to soluble sugars, en route to biofuels. In this context, designer cellulosomes are artificially assembled, chimaeric protein complexes that are used as a tool to comparatively study cellulose degradation by different enzymatic paradigms, and could also serve to improve cellulose deconstruction. Various molecular biology techniques are employed in order to design and engineer the various components of designer cellulosomes. In this chapter, we describe the cloning processes through which the appropriate modules are selected and assembled at the molecular level.
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Affiliation(s)
- Amaranta Kahn
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Edward A Bayer
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel.
| | - Sarah Moraïs
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
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13
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Zhivin O, Dassa B, Moraïs S, Utturkar SM, Brown SD, Henrissat B, Lamed R, Bayer EA. Unique organization and unprecedented diversity of the Bacteroides (Pseudobacteroides) cellulosolvens cellulosome system. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:211. [PMID: 28912832 PMCID: PMC5590126 DOI: 10.1186/s13068-017-0898-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 08/29/2017] [Indexed: 05/23/2023]
Abstract
BACKGROUND (Pseudo) Bacteroides cellulosolvens is an anaerobic, mesophilic, cellulolytic, cellulosome-producing clostridial bacterium capable of utilizing cellulose and cellobiose as carbon sources. Recently, we sequenced the B. cellulosolvens genome, and subsequent comprehensive bioinformatic analysis, herein reported, revealed an unprecedented number of cellulosome-related components, including 78 cohesin modules scattered among 31 scaffoldins and more than 200 dockerin-bearing ORFs. In terms of numbers, the B. cellulosolvens cellulosome system represents the most intricate, compositionally diverse cellulosome system yet known in nature. RESULTS The organization of the B. cellulosolvens cellulosome is unique compared to previously described cellulosome systems. In contrast to all other known cellulosomes, the cohesin types are reversed for all scaffoldins i.e., the type II cohesins are located on the enzyme-integrating primary scaffoldin, whereas the type I cohesins are located on the anchoring scaffoldins. Many of the type II dockerin-bearing ORFs include X60 modules, which are known to stabilize type II cohesin-dockerin interactions. In the present work, we focused on revealing the architectural arrangement of cellulosome structure in this bacterium by examining numerous interactions between the various cohesin and dockerin modules. In total, we cloned and expressed 43 representative cohesins and 27 dockerins. The results revealed various possible architectures of cell-anchored and cell-free cellulosomes, which serve to assemble distinctive cellulosome types via three distinct cohesin-dockerin specificities: type I, type II, and a novel-type designated R (distinct from type III interactions, predominant in ruminococcal cellulosomes). CONCLUSIONS The results of this study provide novel insight into the architecture and function of the most intricate and extensive cellulosomal system known today, thereby extending significantly our overall knowledge base of cellulosome systems and their components. The robust cellulosome system of B. cellulosolvens, with its unique binding specificities and reversal of cohesin-dockerin types, has served to amend our view of the cellulosome paradigm. Revealing new cellulosomal interactions and arrangements is critical for designing high-efficiency artificial cellulosomes for conversion of plant-derived cellulosic biomass towards improved production of biofuels.
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Affiliation(s)
- Olga Zhivin
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Bareket Dassa
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Sarah Moraïs
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Sagar M. Utturkar
- Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37919 USA
- BioEnergy Science Center, Oak Ridge, TN USA
| | - Steven D. Brown
- Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37919 USA
- BioEnergy Science Center, Oak Ridge, TN USA
- Biosciences Division, Energy and Environment Directorate, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Bernard Henrissat
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille University and CNRS, Marseille, France
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Edward A. Bayer
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
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14
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Szczupak A, Aizik D, Moraïs S, Vazana Y, Barak Y, Bayer EA, Alfonta L. The Electrosome: A Surface-Displayed Enzymatic Cascade in a Biofuel Cell's Anode and a High-Density Surface-Displayed Biocathodic Enzyme. NANOMATERIALS (BASEL, SWITZERLAND) 2017; 7:E153. [PMID: 28644390 PMCID: PMC5535219 DOI: 10.3390/nano7070153] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 06/12/2017] [Accepted: 06/20/2017] [Indexed: 11/29/2022]
Abstract
The limitation of surface-display systems in biofuel cells to a single redox enzyme is a major drawback of hybrid biofuel cells, resulting in a low copy-number of enzymes per yeast cell and a limitation in displaying enzymatic cascades. Here we present the electrosome, a novel surface-display system based on the specific interaction between the cellulosomal scaffoldin protein and a cascade of redox enzymes that allows multiple electron-release by fuel oxidation. The electrosome is composed of two compartments: (i) a hybrid anode, which consists of dockerin-containing enzymes attached specifically to cohesin sites in the scaffoldin to assemble an ethanol oxidation cascade, and (ii) a hybrid cathode, which consists of a dockerin-containing oxygen-reducing enzyme attached in multiple copies to the cohesin-bearing scaffoldin. Each of the two compartments was designed, displayed, and tested separately. The new hybrid cell compartments displayed enhanced performance over traditional biofuel cells; in the anode, the cascade of ethanol oxidation demonstrated higher performance than a cell with just a single enzyme. In the cathode, a higher copy number per yeast cell of the oxygen-reducing enzyme copper oxidase has reduced the effect of competitive inhibition resulting from yeast oxygen consumption. This work paves the way for the assembly of more complex cascades using different enzymes and larger scaffoldins to further improve the performance of hybrid cells.
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Affiliation(s)
- Alon Szczupak
- Department of Life Sciences and the Ilse Katz Institute for Nanoscale Science and Technology, P.O. Box 653, 8410501 Beer-Sheva, Israel.
| | - Dror Aizik
- Department of Life Sciences and the Ilse Katz Institute for Nanoscale Science and Technology, P.O. Box 653, 8410501 Beer-Sheva, Israel.
| | - Sarah Moraïs
- Department of Biomolecular Sciences, Weizmann Institute of Science, 234 Herzl St., P.O. Box 26, 7610001 Rehovot, Israel.
| | - Yael Vazana
- Department of Biomolecular Sciences, Weizmann Institute of Science, 234 Herzl St., P.O. Box 26, 7610001 Rehovot, Israel.
| | - Yoav Barak
- Department of Chemical Research Support, Weizmann Institute of Science, 234 Herzl St., P.O. Box 26, 7610001 Rehovot, Israel.
| | - Edward A Bayer
- Department of Biomolecular Sciences, Weizmann Institute of Science, 234 Herzl St., P.O. Box 26, 7610001 Rehovot, Israel.
| | - Lital Alfonta
- Department of Life Sciences and the Ilse Katz Institute for Nanoscale Science and Technology, P.O. Box 653, 8410501 Beer-Sheva, Israel.
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15
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Continually emerging mechanistic complexity of the multi-enzyme cellulosome complex. Curr Opin Struct Biol 2017; 44:151-160. [DOI: 10.1016/j.sbi.2017.03.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 03/16/2017] [Accepted: 03/17/2017] [Indexed: 12/20/2022]
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16
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Development of Synthetic Microbial Platforms to Convert Lignocellulosic Biomass to Biofuels. ADVANCES IN BIOENERGY 2017. [DOI: 10.1016/bs.aibe.2016.12.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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17
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Stern J, Artzi L, Moraïs S, Fontes CMGA, Bayer EA. Carbohydrate Depolymerization by Intricate Cellulosomal Systems. Methods Mol Biol 2017; 1588:93-116. [PMID: 28417363 DOI: 10.1007/978-1-4939-6899-2_8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cellulosomes are multi-enzymatic nanomachines that have been fine-tuned through evolution to efficiently deconstruct plant biomass. Integration of cellulosomal components occurs via highly ordered protein-protein interactions between the various enzyme-borne dockerin modules and the multiple copies of the cohesin modules located on the scaffoldin subunit. Recently, designer cellulosome technology has been established to provide insights into the architectural role of catalytic (enzymatic) and structural (scaffoldin) cellulosomal constituents for the efficient degradation of plant cell wall polysaccharides. Owing to advances in genomics and proteomics, highly structured cellulosome complexes have recently been unraveled, and the information gained has inspired the development of designer cellulosome technology to new levels of complex organization. These higher-order designer cellulosomes have in turn fostered our capacity to enhance the catalytic potential of artificial cellulolytic complexes. In this chapter, methods to produce and employ such intricate cellulosomal complexes are reported.
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Affiliation(s)
- Johanna Stern
- Faculty of Biochemistry, Department of Biomolecular Sciences, The Weizmann Institute of Science, Ullmann Building of Life Sciences, Room 226, Rehovot, 76100, Israel
| | - Lior Artzi
- Faculty of Biochemistry, Department of Biomolecular Sciences, The Weizmann Institute of Science, Ullmann Building of Life Sciences, Room 226, Rehovot, 76100, Israel
| | - Sarah Moraïs
- Faculty of Biochemistry, Department of Biomolecular Sciences, The Weizmann Institute of Science, Ullmann Building of Life Sciences, Room 226, Rehovot, 76100, Israel
| | - Carlos M G A Fontes
- CIISA - Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477, Lisbon, Portugal
| | - Edward A Bayer
- Faculty of Biochemistry, Department of Biomolecular Sciences, The Weizmann Institute of Science, Ullmann Building of Life Sciences, Room 226, Rehovot, 76100, Israel.
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18
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Bensoussan L, Moraïs S, Dassa B, Friedman N, Henrissat B, Lombard V, Bayer EA, Mizrahi I. Broad phylogeny and functionality of cellulosomal components in the bovine rumen microbiome. Environ Microbiol 2016; 19:185-197. [PMID: 27712009 PMCID: PMC6487960 DOI: 10.1111/1462-2920.13561] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 09/29/2016] [Indexed: 11/30/2022]
Abstract
The cellulosome is an extracellular multi‐enzyme complex that is considered one of the most efficient plant cell wall‐degrading strategies devised by nature. Its unique modular architecture, achieved by high affinity and specific interaction between protein modules (cohesins and dockerins) enables formation of various enzyme combinations. Extensive research has been dedicated to the mechanistic nature of the cellulosome complex. Nevertheless, little is known regarding its distribution and abundance among microbes in natural plant fibre‐rich environments. Here, we explored these questions in bovine rumen microbial communities, specialized in efficient degradation of lignocellulosic plant material. We bioinformatically screened for cellulosomal modules in this complex environment using a previously published ultra‐deep fibre‐adherent rumen metagenome. Intriguingly, a large portion of the functions of the dockerin‐containing proteins were related to alternative biological processes, and not necessarily to the classic fibre degradation function. Our analysis was experimentally validated by characterizing specific interactions between selected cohesins and dockerins and revealed that cellulosome is a more generalized strategy used by diverse bacteria, some of which were not previously associated with cellulosome production. Remarkably, our results provide additional proof of similarity among rumen microbial communities worldwide. This study suggests a broader and widespread role for the cellulosomal machinery in nature.
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Affiliation(s)
- Lizi Bensoussan
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Sarah Moraïs
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Bareket Dassa
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Nir Friedman
- The Faculty of Natural Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Bernard Henrissat
- Architecture et Fonction des Macromolécules Biologiques, UMR6098, Aix-Marseille University, CNRS UMR7257, Marseille, France
| | - Vincent Lombard
- Architecture et Fonction des Macromolécules Biologiques, UMR6098, Aix-Marseille University, CNRS UMR7257, Marseille, France
| | - Edward A Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Itzhak Mizrahi
- The Faculty of Natural Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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19
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Galanopoulou AP, Moraïs S, Georgoulis A, Morag E, Bayer EA, Hatzinikolaou DG. Insights into the functionality and stability of designer cellulosomes at elevated temperatures. Appl Microbiol Biotechnol 2016; 100:8731-43. [PMID: 27207145 DOI: 10.1007/s00253-016-7594-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 04/23/2016] [Accepted: 04/28/2016] [Indexed: 01/21/2023]
Abstract
Enzymatic breakdown of lignocellulose is a major limiting step in second generation biorefineries. Assembly of the necessary activities into designer cellulosomes increases the productivity of this step by enhancing enzyme synergy through the proximity effect. However, most cellulosomal components are obtained from mesophilic microorganisms, limiting the applications to temperatures up to 50 °C. We hypothesized that a scaffoldin, comprising modular components of mainly mesophilic origin, can function at higher temperatures when combined with thermophilic enzymes, and the resulting designer cellulosomes could be employed in higher temperature reactions. For this purpose, we used a tetravalent scaffoldin constituted of three cohesins of mesophilic origin as well as a cohesin and cellulose-binding module derived from the thermophilic bacterium Clostridium thermocellum. The scaffoldin was combined with four thermophilic enzymes from Geobacillus and Caldicellulosiruptor species, each fused with a dockerin whose specificity matched one of the cohesins. We initially verified that the biochemical properties and thermal stability of the resulting chimeric enzymes were not affected by the presence of the mesophilic dockerins. Then we examined the stability of the individual single-enzyme-scaffoldin complexes and the full tetravalent cellulosome showing that all complexes are stable and functional for at least 6 h at 60 °C. Finally, within this time frame and conditions, the full complex appeared over 50 % more efficient in the hydrolysis of corn stover compared to the free enzymes. Overall, the results support the utilization of scaffoldin components of mesophilic origin at relatively high temperatures and provide a framework for the production of designer cellulosomes suitable for high temperature biorefinery applications.
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Affiliation(s)
- Anastasia P Galanopoulou
- Faculty of Biology, Microbiology Group, National and Kapodistrian University of Athens, Zografou Campus, 15784, Zografou, Attica, Greece
| | - Sarah Moraïs
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 76100, Rehovot, Israel
| | - Anastasios Georgoulis
- Faculty of Biology, Microbiology Group, National and Kapodistrian University of Athens, Zografou Campus, 15784, Zografou, Attica, Greece
| | - Ely Morag
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 76100, Rehovot, Israel
| | - Edward A Bayer
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 76100, Rehovot, Israel
| | - Dimitris G Hatzinikolaou
- Faculty of Biology, Microbiology Group, National and Kapodistrian University of Athens, Zografou Campus, 15784, Zografou, Attica, Greece.
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20
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Davidi L, Moraïs S, Artzi L, Knop D, Hadar Y, Arfi Y, Bayer EA. Toward combined delignification and saccharification of wheat straw by a laccase-containing designer cellulosome. Proc Natl Acad Sci U S A 2016; 113:10854-9. [PMID: 27621442 PMCID: PMC5047212 DOI: 10.1073/pnas.1608012113] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Efficient breakdown of lignocellulose polymers into simple molecules is a key technological bottleneck limiting the production of plant-derived biofuels and chemicals. In nature, plant biomass degradation is achieved by the action of a wide range of microbial enzymes. In aerobic microorganisms, these enzymes are secreted as discrete elements in contrast to certain anaerobic bacteria, where they are assembled into large multienzyme complexes termed cellulosomes. These complexes allow for very efficient hydrolysis of cellulose and hemicellulose due to the spatial proximity of synergistically acting enzymes and to the limited diffusion of the enzymes and their products. Recently, designer cellulosomes have been developed to incorporate foreign enzymatic activities in cellulosomes so as to enhance lignocellulose hydrolysis further. In this study, we complemented a cellulosome active on cellulose and hemicellulose by addition of an enzyme active on lignin. To do so, we designed a dockerin-fused variant of a recently characterized laccase from the aerobic bacterium Thermobifida fusca The resultant chimera exhibited activity levels similar to the wild-type enzyme and properly integrated into the designer cellulosome. The resulting complex yielded a twofold increase in the amount of reducing sugars released from wheat straw compared with the same system lacking the laccase. The unorthodox use of aerobic enzymes in designer cellulosome machinery effects simultaneous degradation of the three major components of the plant cell wall (cellulose, hemicellulose, and lignin), paving the way for more efficient lignocellulose conversion into soluble sugars en route to alternative fuels production.
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Affiliation(s)
- Lital Davidi
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sarah Moraïs
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Lior Artzi
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Doriv Knop
- Faculty of Agricultural, Food, and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Yitzhak Hadar
- Faculty of Agricultural, Food, and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Yonathan Arfi
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Edward A Bayer
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel;
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21
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Gunnoo M, Cazade PA, Galera-Prat A, Nash MA, Czjzek M, Cieplak M, Alvarez B, Aguilar M, Karpol A, Gaub H, Carrión-Vázquez M, Bayer EA, Thompson D. Nanoscale Engineering of Designer Cellulosomes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:5619-47. [PMID: 26748482 DOI: 10.1002/adma.201503948] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 10/01/2015] [Indexed: 05/27/2023]
Abstract
Biocatalysts showcase the upper limit obtainable for high-speed molecular processing and transformation. Efforts to engineer functionality in synthetic nanostructured materials are guided by the increasing knowledge of evolving architectures, which enable controlled molecular motion and precise molecular recognition. The cellulosome is a biological nanomachine, which, as a fundamental component of the plant-digestion machinery from bacterial cells, has a key potential role in the successful development of environmentally-friendly processes to produce biofuels and fine chemicals from the breakdown of biomass waste. Here, the progress toward so-called "designer cellulosomes", which provide an elegant alternative to enzyme cocktails for lignocellulose breakdown, is reviewed. Particular attention is paid to rational design via computational modeling coupled with nanoscale characterization and engineering tools. Remaining challenges and potential routes to industrial application are put forward.
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Affiliation(s)
- Melissabye Gunnoo
- Materials and Surface Science Institute and Department of Physics and Energy, University of Limerick, Limerick, Ireland
| | - Pierre-André Cazade
- Materials and Surface Science Institute and Department of Physics and Energy, University of Limerick, Limerick, Ireland
| | - Albert Galera-Prat
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas (CSIC), IMDEA Nanociencias and CIBERNED, Madrid, Spain
| | - Michael A Nash
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-University, 80799, Munich, Germany
| | - Mirjam Czjzek
- Sorbonne Universités, UPMC, Université Paris 06, and Centre National de la Recherche Scientifique, UMR 8227, Integrative Biology of Marine Models, Station Biologique, de Roscoff, CS 90074, F-29688, Roscoff cedex, Bretagne, France
| | - Marek Cieplak
- Laboratory of Biological Physics, Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Beatriz Alvarez
- Biopolis S.L., Parc Científic de la Universitat de Valencia, Edificio 2, C/Catedrático Agustín Escardino 9, 46980, Paterna (Valencia), Spain
| | - Marina Aguilar
- Abengoa, S.A., Palmas Altas, Calle Energía Solar nº 1, 41014, Seville, Spain
| | - Alon Karpol
- Designer Energy Ltd., 2 Bergman St., Tamar Science Park, Rehovot, 7670504, Israel
| | - Hermann Gaub
- Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-University, 80799, Munich, Germany
| | - Mariano Carrión-Vázquez
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas (CSIC), IMDEA Nanociencias and CIBERNED, Madrid, Spain
| | - Edward A Bayer
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Damien Thompson
- Materials and Surface Science Institute and Department of Physics and Energy, University of Limerick, Limerick, Ireland
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22
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Cunha ES, Hatem CL, Barrick D. Synergistic enhancement of cellulase pairs linked by consensus ankyrin repeats: Determination of the roles of spacing, orientation, and enzyme identity. Proteins 2016; 84:1043-54. [PMID: 27071357 DOI: 10.1002/prot.25047] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 03/09/2016] [Accepted: 03/25/2016] [Indexed: 12/22/2022]
Abstract
Biomass deconstruction to small simple sugars is a potential approach to biofuels production; however, the highly recalcitrant nature of biomass limits the economic viability of this approach. Thus, research on efficient biomass degradation is necessary to achieve large-scale production of biofuels. Enhancement of cellulolytic activity by increasing synergism between cellulase enzymes holds promise in achieving high-yield biofuels production. Here we have inserted cellulase pairs from extremophiles into hyperstable α-helical consensus ankyrin repeat domain scaffolds. Such chimeric constructs allowed us to optimize arrays of enzyme pairs against a variety of cellulolytic substrates. We found that endocellulolytic domains CelA (CA) and Cel12A (C12A) act synergistically in the context of ankyrin repeats, with both three and four repeat spacing. The extent of synergy differs for different substrates. Also, having C12A N-terminal to CA provides greater synergy than the reverse construct, especially against filter paper. In contrast, we do not see synergy for these enzymes in tandem with CelK (CK) catalytic domain, a larger exocellulase, demonstrating the importance of enzyme identity in synergistic enhancement. Furthermore, we found endocellulases CelD and CA with three repeat spacing to act synergistically against filter paper. Importantly, connecting CA and C12A with a disordered linker of similar contour length shows no synergistic enhancement, indicating that synergism results from connecting these domains with folded ankyrin repeats. These results show that ankyrin arrays can be used to vary spacing and orientation between enzymes, helping to design and optimize artificial cellulosomes, providing a novel architecture for synergistic enhancement of enzymatic cellulose degradation. Proteins 2016; 84:1043-1054. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Eva S Cunha
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 N. Charles St, Baltimore, Maryland, 21218.,Department of Structural Biology, Max Plank Institute of Biophysics, Max-von-Laue-Str. 3, Frankfurt am Main, D-60438, Germany
| | - Christine L Hatem
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 N. Charles St, Baltimore, Maryland, 21218
| | - Doug Barrick
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 N. Charles St, Baltimore, Maryland, 21218
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23
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Arora R, Behera S, Sharma NK, Kumar S. Bioprospecting thermostable cellulosomes for efficient biofuel production from lignocellulosic biomass. BIORESOUR BIOPROCESS 2015. [DOI: 10.1186/s40643-015-0066-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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24
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Sainz-Polo MA, González B, Menéndez M, Pastor FIJ, Sanz-Aparicio J. Exploring Multimodularity in Plant Cell Wall Deconstruction: STRUCTURAL AND FUNCTIONAL ANALYSIS OF Xyn10C CONTAINING THE CBM22-1-CBM22-2 TANDEM. J Biol Chem 2015; 290:17116-30. [PMID: 26001782 DOI: 10.1074/jbc.m115.659300] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Indexed: 11/06/2022] Open
Abstract
Elucidating the molecular mechanisms regulating multimodularity is a challenging task. Paenibacillus barcinonensis Xyn10C is a 120-kDa modular enzyme that presents the CBM22/GH10/CBM9 architecture found in a subset of large xylanases. We report here the three-dimensional structure of the Xyn10C N-terminal region, containing the xylan-binding CBM22-1-CBM22-2 tandem (Xyn10C-XBD), which represents the first solved crystal structure of two contiguous CBM22 modules. Xyn10C-XBD is folded into two separate CBM22 modules linked by a flexible segment that endows the tandem with extraordinary plasticity. Each isolated domain has been expressed and crystallized, and their binding abilities have been investigated. Both domains contain the R(W/Y)YYE motif required for xylan binding. However, crystallographic analysis of CBM22-2 complexes shows Trp-308 as an additional binding determinant. The long loop containing Trp-308 creates a platform that possibly contributes to the recognition of precise decorations at subsite S2. CBM22-2 may thus define a subset of xylan-binding CBM22 modules directed to particular regions of the polysaccharide. Affinity electrophoresis reveals that Xyn10C-XBD binds arabinoxylans more tightly, which is more apparent when CBM22-2 is tested against highly substituted xylan. The crystal structure of the catalytic domain, also reported, shows the capacity of the active site to accommodate xylan substitutions at almost all subsites. The structural differences found at both Xyn10C-XBD domains are consistent with the isothermal titration calorimetry experiments showing two sites with different affinities in the tandem. On the basis of the distinct characteristics of CBM22, a delivery strategy of Xyn10C mediated by Xyn10C-XBD is proposed.
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Affiliation(s)
| | - Beatriz González
- From the Departamentos de Cristalografía y Biología Estructural y
| | - Margarita Menéndez
- Química Física Biólogica, Instituto de Química-Física Rocasolano, Consejo Superior de Investigaciones Científicas, Serrano 119, 28006-Madrid and
| | - F I Javier Pastor
- the Departamento de Microbiología, Facultad de Biología, Universidad de Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain
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25
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Noda S, Matsumoto T, Tanaka T, Kondo A. Secretory production of tetrameric native full-length streptavidin with thermostability using Streptomyces lividans as a host. Microb Cell Fact 2015; 14:5. [PMID: 25582841 PMCID: PMC4328045 DOI: 10.1186/s12934-014-0188-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Accepted: 12/26/2014] [Indexed: 12/04/2022] Open
Abstract
Background Streptavidin is a tetrameric protein derived from Streptomyces avidinii, and has tight and specific biotin binding affinity. Applications of the streptavidin-biotin system have been widely studied. Streptavidin is generally produced using protein expression in Escherichia coli. In the present study, the secretory production of streptavidin was carried out using Streptomyces lividans as a host. Results In this study, we used the gene encoding native full-length streptavidin, whereas the core region is generally used for streptavidin production in E. coli. Tetrameric streptavidin composed of native full-length streptavidin monomers was successfully secreted in the culture supernatant of S. lividans transformants, and had specific biotin binding affinity as strong as streptavidin produced by E. coli. The amount of Sav using S. lividans was about 9 times higher than using E. coli. Surprisingly, streptavidin produced by S. lividans exhibited affinity to biotin after boiling, despite the fact that tetrameric streptavidin is known to lose its biotin binding ability after brief boiling. Conclusion We successfully produced a large amount of tetrameric streptavidin as a secretory-form protein with unique thermotolerance. Electronic supplementary material The online version of this article (doi:10.1186/s12934-014-0188-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Shuhei Noda
- Biomass Engineering Program, RIKEN, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan.
| | - Takuya Matsumoto
- Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan.
| | - Tsutomu Tanaka
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan.
| | - Akihiko Kondo
- Biomass Engineering Program, RIKEN, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan. .,Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan.
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26
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Matsumoto T, Shimada S, Hata Y, Tanaka T, Kondo A. Multi-functional glycoside hydrolase: Blon_0625 from Bifidobacterium longum subsp. infantis ATCC 15697. Enzyme Microb Technol 2014; 68:10-4. [PMID: 25435500 DOI: 10.1016/j.enzmictec.2014.10.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 10/14/2014] [Accepted: 10/14/2014] [Indexed: 10/24/2022]
Abstract
We here describe a unique β-D-glucosidase (BGL; Blon_0625) derived from Bifidobacterium longum subsp. infantis ATCC 15697. The Blon_0625 gene was expressed by recombinant Escherichia coli. Purified recombinant Blon_0625 retains hydrolyzing activity against both p-nitrophenyl-β-D-glucopyranoside (pNPG; 17.3±0.24Umg(-1)) and p-nitrophenyl-β-D-xylopyranoside (pNPX; 16.7±0.32Umg(-1)) at pH 6.0, 30°C. To best of our knowledge, no previously described BGL retains the same level of both pNPGase and pNPXase activity. Furthermore, Blon_0625 also retains the activity against 4-nitrophenyl-α-l-arabinofranoside (pNPAf; 5.6±0.09Umg(-1)). In addition, the results of the degradation of phosphoric acid swollen cellulose (PASC) or xylan using endoglucanase from Thermobifida fusca YX (Tfu_0901) or xylanase from Kitasatospora setae KM-6054 (KSE_59480) show that Blon_0625 acts as a BGL and as a β-D-xylosidase (XYL) for hydrolyzing oligosaccharides. These results clearly indicate that Blon_0625 is a multi-functional glycoside hydrolase which retains the activity of BGL, XYL, and also α-l-arabinofuranosidase. Therefore, the utilization of multi-functional Blon_0625 may contribute to facilitating the efficient degradation of lignocellulosic materials and help enhance bioconversion processes.
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Affiliation(s)
- Takuya Matsumoto
- Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodaicho, Nada, Kobe 657-8501, Japan
| | - Shota Shimada
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada, Kobe 657-8501, Japan
| | - Yuto Hata
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada, Kobe 657-8501, Japan
| | - Tsutomu Tanaka
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada, Kobe 657-8501, Japan.
| | - Akihiko Kondo
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada, Kobe 657-8501, Japan
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Thomas L, Joseph A, Gottumukkala LD. Xylanase and cellulase systems of Clostridium sp.: an insight on molecular approaches for strain improvement. BIORESOURCE TECHNOLOGY 2014; 158:343-50. [PMID: 24581864 DOI: 10.1016/j.biortech.2014.01.140] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 01/23/2014] [Accepted: 01/27/2014] [Indexed: 05/21/2023]
Abstract
Bioethanol and biobutanol hold great promise as alternative biofuels, especially for transport sector, because they can be produced from lignocellulosic agro-industrial residues. From techno-economic point of view, the bioprocess for biofuels production should involve minimal processing steps. Consolidated bioprocessing (CBP), which combines various processing steps such as pretreatment, hydrolysis and fermentation in a single bioreactor, could be of great relevance for the production of bioethanol and biobutanol or solvents (acetone, butanol, ethanol), employing clostridia. For CBP, Clostridium holds best promise because it possesses multi-enzyme system involving cellulosome and xylanosome, which comprise several enzymes such as cellulases and xylanases. The aim of this article was to review the recent developments on enzyme systems of clostridia, especially xylanase and cellulase with an effort to analyse the information available on molecular approaches for the improvement of strains with ultimate aim to improve the efficiencies of hydrolysis and fermentation.
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Affiliation(s)
- Leya Thomas
- Biotechnology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum 695 019, India.
| | - Abhilash Joseph
- Department of Biotechnology & Microbiology, Kannur University, Thalassery Campus, Kannur 670 661, India
| | - Lalitha Devi Gottumukkala
- Biotechnology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum 695 019, India
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Vazana Y, Barak Y, Unger T, Peleg Y, Shamshoum M, Ben-Yehezkel T, Mazor Y, Shapiro E, Lamed R, Bayer EA. A synthetic biology approach for evaluating the functional contribution of designer cellulosome components to deconstruction of cellulosic substrates. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:182. [PMID: 24341331 PMCID: PMC3878649 DOI: 10.1186/1754-6834-6-182] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 11/27/2013] [Indexed: 05/04/2023]
Abstract
BACKGROUND Select cellulolytic bacteria produce multi-enzymatic cellulosome complexes that bind to the plant cell wall and catalyze its efficient degradation. The multi-modular interconnecting cellulosomal subunits comprise dockerin-containing enzymes that bind cohesively to cohesin-containing scaffoldins. The organization of the modules into functional polypeptides is achieved by intermodular linkers of different lengths and composition, which provide flexibility to the complex and determine its overall architecture. RESULTS Using a synthetic biology approach, we systematically investigated the spatial organization of the scaffoldin subunit and its effect on cellulose hydrolysis by designing a combinatorial library of recombinant trivalent designer scaffoldins, which contain a carbohydrate-binding module (CBM) and 3 divergent cohesin modules. The positions of the individual modules were shuffled into 24 different arrangements of chimaeric scaffoldins. This basic set was further extended into three sub-sets for each arrangement with intermodular linkers ranging from zero (no linkers), 5 (short linkers) and native linkers of 27-35 amino acids (long linkers). Of the 72 possible scaffoldins, 56 were successfully cloned and 45 of them expressed, representing 14 full sets of chimaeric scaffoldins. The resultant 42-component scaffoldin library was used to assemble designer cellulosomes, comprising three model C. thermocellum cellulases. Activities were examined using Avicel as a pure microcrystalline cellulose substrate and pretreated cellulose-enriched wheat straw as a model substrate derived from a native source. All scaffoldin combinations yielded active trivalent designer cellulosome assemblies on both substrates that exceeded the levels of the free enzyme systems. A preferred modular arrangement for the trivalent designer scaffoldin was not observed for the three enzymes used in this study, indicating that they could be integrated at any position in the designer cellulosome without significant effect on cellulose-degrading activity. Designer cellulosomes assembled with the long-linker scaffoldins achieved higher levels of activity, compared to those assembled with short-and no-linker scaffoldins. CONCLUSIONS The results demonstrate the robustness of the cellulosome system. Long intermodular scaffoldin linkers are preferable, thus leading to enhanced degradation of cellulosic substrates, presumably due to the increased flexibility and spatial positioning of the attached enzymes in the complex. These findings provide a general basis for improved designer cellulosome systems as a platform for bioethanol production.
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Affiliation(s)
- Yael Vazana
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yoav Barak
- Chemical Research Support, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tamar Unger
- Structural Proteomics, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yoav Peleg
- Structural Proteomics, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Melina Shamshoum
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tuval Ben-Yehezkel
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
- Department of Computer Science and Applied Mathematics, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yair Mazor
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
- Department of Computer Science and Applied Mathematics, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ehud Shapiro
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
- Department of Computer Science and Applied Mathematics, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Edward A Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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Slutzki M, Jobby MK, Chitayat S, Karpol A, Dassa B, Barak Y, Lamed R, Smith SP, Bayer EA. Intramolecular clasp of the cellulosomal Ruminococcus flavefaciens ScaA dockerin module confers structural stability. FEBS Open Bio 2013; 3:398-405. [PMID: 24251102 PMCID: PMC3821032 DOI: 10.1016/j.fob.2013.09.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 09/20/2013] [Accepted: 09/20/2013] [Indexed: 12/02/2022] Open
Abstract
The cellulosome is a large extracellular multi-enzyme complex that facilitates the efficient hydrolysis and degradation of crystalline cellulosic substrates. During the course of our studies on the cellulosome of the rumen bacterium Ruminococcus flavefaciens, we focused on the critical ScaA dockerin (ScaADoc), the unique dockerin that incorporates the primary enzyme-integrating ScaA scaffoldin into the cohesin-bearing ScaB adaptor scaffoldin. In the absence of a high-resolution structure of the ScaADoc module, we generated a computational model, and, upon its analysis, we were surprised to discover a putative stacking interaction between an N-terminal Trp and a C-terminal Pro, which we termed intramolecular clasp. In order to verify the existence of such an interaction, these residues were mutated to alanine. Circular dichroism spectroscopy, intrinsic tryptophan and ANS fluorescence, and NMR spectroscopy indicated that mutation of these residues has a destabilizing effect on the functional integrity of the Ca2+-bound form of ScaADoc. Analysis of recently determined dockerin structures from other species revealed the presence of other well-defined intramolecular clasps, which consist of different types of interactions between selected residues at the dockerin termini. We propose that this thematic interaction may represent a major distinctive structural feature of the dockerin module. A structural model for the Ruminococcus flavefaciens ScaA dockerin is proposed. A stacking interaction between N- and C-terminal residues was derived from the model. Mutations of putative interacting residues resulted in reduced stability and binding. Similar intramodular “clasp” interactions were observed in other dockerin structures.
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Key Words
- ANS, 8-anilino-1-naphthalenesulfonate
- CBM, carbohydrate-binding module family 3a from C. thermocellum
- Cc, Clostridium cellulolyticum
- Coh, cohesin
- Cohesin
- Ct, Clostridium thermocellum
- Doc, dockerin
- HBS, hepes-buffered saline
- IPTG, isopropyl-1-thio-β-d-galactoside
- Protein stability
- Scaffoldin
- Stacking interaction
- TMB, 3,3′,5,5′-tetramethylbenzidine
- Xyn, xylanase T6 from Geobacillus stearothemophilus
- cELISA, competitive enzyme-linked interaction assay
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Affiliation(s)
- Michal Slutzki
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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30
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Lee SJ, Lee SJ, Lee DW. Design and development of synthetic microbial platform cells for bioenergy. Front Microbiol 2013; 4:92. [PMID: 23626588 PMCID: PMC3630320 DOI: 10.3389/fmicb.2013.00092] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 04/03/2013] [Indexed: 12/26/2022] Open
Abstract
The finite reservation of fossil fuels accelerates the necessity of development of renewable energy sources. Recent advances in synthetic biology encompassing systems biology and metabolic engineering enable us to engineer and/or create tailor made microorganisms to produce alternative biofuels for the future bio-era. For the efficient transformation of biomass to bioenergy, microbial cells need to be designed and engineered to maximize the performance of cellular metabolisms for the production of biofuels during energy flow. Toward this end, two different conceptual approaches have been applied for the development of platform cell factories: forward minimization and reverse engineering. From the context of naturally minimized genomes,non-essential energy-consuming pathways and/or related gene clusters could be progressively deleted to optimize cellular energy status for bioenergy production. Alternatively, incorporation of non-indigenous parts and/or modules including biomass-degrading enzymes, carbon uptake transporters, photosynthesis, CO2 fixation, and etc. into chassis microorganisms allows the platform cells to gain novel metabolic functions for bioenergy. This review focuses on the current progress in synthetic biology-aided pathway engineering in microbial cells and discusses its impact on the production of sustainable bioenergy.
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Affiliation(s)
- Sang Jun Lee
- Systems and Synthetic Biology Research Center, Korea Research Institute of Bioscience and Biotechnology Daejeon, South Korea
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31
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Moraïs S, Barak Y, Lamed R, Wilson DB, Xu Q, Himmel ME, Bayer EA. Paradigmatic status of an endo- and exoglucanase and its effect on crystalline cellulose degradation. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:78. [PMID: 23095278 PMCID: PMC3502487 DOI: 10.1186/1754-6834-5-78] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 10/19/2012] [Indexed: 05/07/2023]
Abstract
BACKGROUND Microorganisms employ a multiplicity of enzymes to efficiently degrade the composite structure of plant cell wall cellulosic polysaccharides. These remarkable enzyme systems include glycoside hydrolases (cellulases, hemicellulases), polysaccharide lyases, and the carbohydrate esterases. To accomplish this challenging task, several strategies are commonly observed either separately or in combination. These include free enzyme systems, multifunctional enzymes, and multi-enzyme self-assembled designer cellulosome complexes. RESULTS In order to compare these different paradigms, we employed a synthetic biology approach to convert two different cellulases from the free enzymatic system of the well-studied bacterium, Thermobifida fusca, into bifunctional enzymes with different modular architectures. We then examined their performance compared to those of the combined parental free-enzyme and equivalent designer-cellulosome systems. The results showed that the cellulolytic activity displayed by the different architectures of the bifunctional enzymes was somewhat inferior to that of the wild-type free enzyme system. CONCLUSIONS The activity exhibited by the designer cellulosome system was equal or superior to that of the free system, presumably reflecting the combined proximity of the enzymes and high flexibility of the designer cellulosome components, thus enabling efficient enzymatic activity of the catalytic modules.
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Affiliation(s)
- Sarah Moraïs
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
- Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 76100, Israel
| | - Yoav Barak
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
- Chemical Research Support, The Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, 69978, Israel
| | - David B Wilson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Qi Xu
- Biosciences Center, National Renewable Energy Laboratory (NREL) and BioEnergy Science Center (BESC), Golden, CO, USA
| | - Michael E Himmel
- Biosciences Center, National Renewable Energy Laboratory (NREL) and BioEnergy Science Center (BESC), Golden, CO, USA
| | - Edward A Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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