scholarly journals Structure of a C1/C4-oxidizing AA9 lytic polysaccharide monooxygenase from the thermophilic fungus Malbranchea cinnamomea

2021 ◽  
Vol 77 (8) ◽  
Author(s):  
Scott Mazurkewich ◽  
Andrea Seveso ◽  
Silvia Hüttner ◽  
Gisela Brändén ◽  
Johan Larsbrink
Keyword(s):  
Plant Cell Wall ◽  
Plant Biomass ◽  
Industrial Applications ◽  
Thermophilic Fungus ◽  
Lytic Polysaccharide Monooxygenase ◽  
Large Loop ◽  
Small Loop ◽  
Polysaccharide Monooxygenases ◽  
Equivalent Residue ◽  
Residue Substitution

The thermophilic fungus Malbranchea cinnamomea contains a host of enzymes that enable its ability as an efficient degrader of plant biomass and that could be mined for industrial applications. This thermophilic fungus has been studied and found to encode eight lytic polysaccharide monooxygenases (LPMOs) from auxiliary activity family 9 (AA9), which collectively possess different substrate specificities for a range of plant cell-wall-related polysaccharides and oligosaccharides. To gain greater insight into the molecular determinants defining the different specificities, structural studies were pursued and the structure of McAA9F was determined. The enzyme contains the immunoglobulin-like fold typical of previously solved AA9 LPMO structures, but contains prominent differences in the loop regions found on the surface of the substrate-binding site. Most significantly, McAA9F has a broad substrate specificity, with activity on both crystalline and soluble polysaccharides. Moreover, it contains a small loop in a region where a large loop has been proposed to govern specificity towards oligosaccharides. The presence of the small loop leads to a considerably flatter and more open surface that is likely to enable the broad specificity of the enzyme. The enzyme contains a succinimide residue substitution, arising from intramolecular cyclization of Asp10, at a position where several homologous members contain an equivalent residue but cyclization has not previously been observed. This first structure of an AA9 LPMO from M. cinnamomea aids both the understanding of this family of enzymes and the exploration of the repertoire of industrially relevant lignocellulolytic enzymes from this fungus.

scholarly journals Oxidoreductases and Reactive Oxygen Species in Conversion of Lignocellulosic Biomass

2018 ◽  
Vol 82 (4) ◽  
Author(s):  
Bastien Bissaro ◽  
Anikó Várnai ◽  
Åsmund K. Røhr ◽  
Vincent G. H. Eijsink
Keyword(s):  
Reactive Oxygen Species ◽  
Plant Cell Wall ◽  
Biomass Conversion ◽  
Hydrolytic Enzymes ◽  
Reactive Oxygen ◽  
Industrial Applications ◽  
Fine Tuning ◽  
Oxygen Species ◽  
Redox Systems ◽  
Polysaccharide Monooxygenases

SUMMARYBiomass constitutes an appealing alternative to fossil resources for the production of materials and energy. The abundance and attractiveness of vegetal biomass come along with challenges pertaining to the intricacy of its structure, evolved during billions of years to face and resist abiotic and biotic attacks. To achieve the daunting goal of plant cell wall decomposition, microorganisms have developed many (enzymatic) strategies, from which we seek inspiration to develop biotechnological processes. A major breakthrough in the field has been the discovery of enzymes today known as lytic polysaccharide monooxygenases (LPMOs), which, by catalyzing the oxidative cleavage of recalcitrant polysaccharides, allow canonical hydrolytic enzymes to depolymerize the biomass more efficiently. Very recently, it has been shown that LPMOs are not classical monooxygenases in that they can also use hydrogen peroxide (H2O2) as an oxidant. This discovery calls for a revision of our understanding of how lignocellulolytic enzymes are connected since H2O2is produced and used by several of them. The first part of this review is dedicated to the LPMO paradigm, describing knowns, unknowns, and uncertainties. We then present different lignocellulolytic redox systems, enzymatic or not, that depend on fluxes of reactive oxygen species (ROS). Based on an assessment of these putatively interconnected systems, we suggest that fine-tuning of H2O2levels and proximity between sites of H2O2production and consumption are important for fungal biomass conversion. In the last part of this review, we discuss how our evolving understanding of redox processes involved in biomass depolymerization may translate into industrial applications.

scholarly journals Identification of the molecular determinants driving the substrate specificity of fungal lytic polysaccharide monooxygenases (LPMOs)

2020 ◽  
pp. jbc.RA120.015545
Author(s):  
Kristian E. H. Frandsen ◽  
Mireille Haon ◽  
Sacha Grisel ◽  
Bernard Henrissat ◽  
Leila Lo Leggio ◽  
...  
Keyword(s):  
Substrate Specificity ◽  
Time Course ◽  
Plant Cell Wall ◽  
Plant Biomass ◽  
Substrate Binding ◽  
Glycoside Hydrolases ◽  
Sequence Alignments ◽  
Lytic Polysaccharide Monooxygenases ◽  
Molecular Determinants ◽  
Polysaccharide Monooxygenases

Understanding enzymatic breakdown of plant biomass is crucial to develop nature-inspired biotechnological processes. Lytic polysaccharide monooxygenases (LPMOs) are microbial enzymes secreted by fungal saprotrophs involved in carbon recycling. LPMOs modify biomass by oxidatively cleaving polysaccharides thereby enhancing the efficiency of glycoside hydrolases. Fungal AA9 LPMOs are active on cellulose but some members also display activity on hemicelluloses and/or oligosaccharides. Although the active site subsites are well defined for a few model LPMOs, the molecular determinants driving broad substrate specificity are still not easily predictable. Based on bioinformatic clustering and sequence alignments, we selected seven fungal AA9 LPMOs that differ in the amino-acid residues constituting their subsites. Investigation of their substrate specificities revealed that all these LPMOs are active on cellulose and cello-oligosaccharides, as well as plant cell wall-derived hemicellulosic polysaccharides and carry out C4 oxidative cleavage. The product profiles from cello-oligosaccharides degradation suggests that the subtle differences in amino acids sequence within the substrate-binding loop regions lead to different preferred binding modes. Our functional analyses allowed us to probe the molecular determinants of substrate binding within two AA9 LPMO sub-clusters. Many wood-degrading fungal species rich in AA9 genes have at least one AA9 enzyme with structural loop features that allow recognition of short β-(1,4)-linked glucan chains. Time-course monitoring of these AA9 LPMOs on cello-oligosaccharides also provides a useful model system for mechanistic studies of LPMO catalysis. These results are valuable for the understanding of LPMO contribution to wood decaying process in nature and for the development of sustainable biorefineries.

scholarly journals Combining pieces: a thorough analysis of light activation boosting power and co-substrate preferences for the catalytic efficiency of lytic polysaccharide monooxygenase MtLPMO9A

2021 ◽  
Vol 8 (3) ◽  
pp. 1454-1464
Author(s):  
Ana Gabriela V. Sepulchro ◽  
Vanessa O.A. Pellegrini ◽  
Lucas D. Dias ◽  
Marco A.S. Kadowaki ◽  
David Cannella ◽  
...  
Keyword(s):  
Plant Biomass ◽  
Biomass Conversion ◽  
Direct Electron Transfer ◽  
Catalytic Efficiency ◽  
Reaction Products ◽  
Lytic Polysaccharide Monooxygenase ◽  
Substrate Preferences ◽  
Polysaccharide Monooxygenases ◽  
Significant Release ◽  
Cost Efficient

Cost-efficient plant biomass conversion using biochemical and/or chemical routes is essential for transitioning to sustainable chemical technologies and renewable biofuels. Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that make part of modern hydrolytic cocktails destined for plant biomass degradation. Here, we characterized MtLPMO9A from Thermothelomyces thermophilus M77 (formerly Myceliophthora thermophila) and demonstrated that it could be efficiently driven by chlorophyllin excited by light in the presence of a reductant agent. However, in the absence of chemical reductant, chlorophyllin and light alone do not lead to a significant release of the reaction products by the LPMO, indicating a low capacity of MtLPMO9A reduction (either via direct electron transfer or via superoxide ion, O2•-). We showed that photocatalysis could significantly increase the LPMO activity against highly crystalline and recalcitrant cellulosic substrates, which are poorly degraded in the absence of chlorophyllin and light. We also evaluated the use of co-substrates by MtLPMO9A, revealing that the enzyme can use both hydrogen peroxide (H2O2) and molecular oxygen (O2) as co-substrates for cellulose catalytic oxidation.

scholarly journals Water-soluble chlorophyll-binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellulose by a lytic polysaccharide monooxygenase

2020 ◽  
Author(s):  
N. Dodge ◽  
D. A. Russo ◽  
B.M. Blossom ◽  
R.K. Singh ◽  
B. van Oort ◽  
...  
Keyword(s):  
Binding Proteins ◽  
Plant Biomass ◽  
Light Exposure ◽  
Water Soluble ◽  
Lytic Polysaccharide Monooxygenase ◽  
Cellulose Oxidation ◽  
Biomass Processing ◽  
Polysaccharide Monooxygenases ◽  
Cellulose Depolymerization

Abstract Background Lytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass. LPMO-driven cellulose oxidation can be enhanced considerably through photobiocatalysis using chlorophyll derivatives and light. Water soluble chlorophyll binding proteins (WSCPs) make it is possible to stabilize and solubilize chlorophyll in aqueous solution, allowing for in vitro studies on photostability and ROS production. Here we aim apply a WSCP-Chl a as a photosensitizing complex for photobiocatalysis with the LPMO, TtAA9. Results We have in this study demonstrated how WSCP reconstituted with chlorophyll a (WSCP-Chl a) can create a stable photosensitizing complex which produces controlled amounts of H2O2 in the presence of ascorbic acid and light. WSCP-Chl a is highly reactive and allows for tightly controlled formation of H2O2 by regulating light intensity. TtAA9 together with WSCP-Chl a shows increased cellulose oxidation under low light conditions, and the WSCP-Chl a complex remains stable after 24 hours of light exposure. Additionally, the WSCP-Chl a complex demonstrates stability over a range of temperatures and pH conditions relevant for enzyme activity in industrial settings. Conclusion With WSCP-Chl a as the photosensitizer, the need to replenish Chl is greatly reduced, enhancing the catalytic lifetime of light-driven LPMOs and increasing the efficiency of cellulose depolymerization. WSCP-Chl a allows for stable photobiocatalysis providing a sustainable solution for biomass processing.

scholarly journals Water-soluble chlorophyll-binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellulose by a lytic polysaccharide monooxygenase

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
N. Dodge ◽  
D. A. Russo ◽  
B. M. Blossom ◽  
R. K. Singh ◽  
B. van Oort ◽  
...  
Keyword(s):  
Binding Proteins ◽  
Plant Biomass ◽  
Light Exposure ◽  
Water Soluble ◽  
Lytic Polysaccharide Monooxygenase ◽  
Cellulose Oxidation ◽  
Biomass Processing ◽  
Polysaccharide Monooxygenases ◽  
Cellulose Depolymerization

Abstract Background Lytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass. LPMO-driven cellulose oxidation can be enhanced considerably through photobiocatalysis using chlorophyll derivatives and light. Water soluble chlorophyll binding proteins (WSCPs) make it is possible to stabilize and solubilize chlorophyll in aqueous solution, allowing for in vitro studies on photostability and ROS production. Here we aim to apply WSCP–Chl a as a photosensitizing complex for photobiocatalysis with the LPMO, TtAA9. Results We have in this study demonstrated how WSCP reconstituted with chlorophyll a (WSCP–Chl a) can create a stable photosensitizing complex which produces controlled amounts of H2O2 in the presence of ascorbic acid and light. WSCP–Chl a is highly reactive and allows for tightly controlled formation of H2O2 by regulating light intensity. TtAA9 together with WSCP–Chl a shows increased cellulose oxidation under low light conditions, and the WSCP–Chl a complex remains stable after 24 h of light exposure. Additionally, the WSCP–Chl a complex demonstrates stability over a range of temperatures and pH conditions relevant for enzyme activity in industrial settings. Conclusion With WSCP–Chl a as the photosensitizer, the need to replenish Chl is greatly reduced, enhancing the catalytic lifetime of light-driven LPMOs and increasing the efficiency of cellulose depolymerization. WSCP–Chl a allows for stable photobiocatalysis providing a sustainable solution for biomass processing.

scholarly journals Synthesis of Glycoconjugates Utilizing the Regioselectivity of a Lytic Polysaccharide Monooxygenase

2020 ◽  
Author(s):  
Bjørge Westereng ◽  
Stjepan K. Kračun ◽  
Shaun Leivers ◽  
Magnus Ø. Arntzen ◽  
Finn L. Aachmann ◽  
...  
Keyword(s):  
Plant Biomass ◽  
Cellulose Degradation ◽  
Hydroxyl Groups ◽  
Carbonyl Groups ◽  
Lytic Polysaccharide Monooxygenase ◽  
Renewable Chemicals ◽  
Polysaccharide Monooxygenases ◽  
Chemical Coupling ◽  
Potential Biodegradability ◽  
Polysaccharide Monooxygenase

ABSTRACTPolysaccharides from plant biomass are the most abundant renewable chemicals on Earth and can potentially be converted to a wide variety of useful glycoconjugates. While anomeric hydroxyl groups of carbohydrates are amenable to a variety of useful chemical modifications, selective cross-coupling to non-reducing ends has remained challenging. Several lytic polysaccharide monooxygenases (LPMOs), powerful enzymes known for their application in cellulose degradation, specifically oxidize non-reducing ends, introducing carbonyl groups that can be utilized for chemical coupling. This study provides a simple and highly specific approach to produce oxime-based glycoconjugates from LPMO-functionalized oligosaccharides. The products are evaluated by HPLC, mass spectrometry and NMR. Furthermore, we demonstrate potential biodegradability of these glycoconjugates using selective enzymes.

scholarly journals Water-soluble chlorophyll-binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellulose by a lytic polysaccharide monooxygenase.

2020 ◽  
Author(s):  
N. Dodge ◽  
D. A. Russo ◽  
B.M. Blossom ◽  
R.K. Singh ◽  
B. van Oort ◽  
...  
Keyword(s):  
Binding Proteins ◽  
Plant Biomass ◽  
Light Exposure ◽  
Water Soluble ◽  
Lytic Polysaccharide Monooxygenase ◽  
Cellulose Oxidation ◽  
Biomass Processing ◽  
Polysaccharide Monooxygenases ◽  
Cellulose Depolymerization

Abstract Background: Lytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass. LPMO-driven cellulose oxidation can be enhanced considerably through photobiocatalysis using chlorophyll derivatives and light. Water soluble chlorophyll binding proteins (WSCPs) make it is possible to stabilize and solubilize chlorophyll in aqueous solution, allowing for in vitro studies on photostability and ROS production. Here we aim apply a WSCP-Chl α as a photosensitizing complex for photobiocatalysis with the LPMO, TtAA9. Results: We have in this study demonstrated how WSCP reconstituted with chlorophyll a (WSCP-Chl α) can create a stable photosensitizing complex which produces controlled amounts of H2O2 in the presence of ascorbic acid and light. WSCP-Chl α is highly reactive and allows for tightly controlled formation of H2O2 by regulating light intensity. TtAA9 together with WSCP-Chl α shows increased cellulose oxidation under low light conditions, and the WSCP-Chl α complex remains stable after 24 hours of light exposure. Additionally, the WSCP-Chl α complex demonstrates stability over a range of temperatures and pH conditions relevant for enzyme activity in industrial settings.Conclusion: With WSCP-Chl α as the photosensitizer, the need to replenish Chl is greatly reduced, enhancing the catalytic lifetime of light-driven LPMOs and increasing the efficiency of cellulose depolymerization. WSCP-Chl α allows for stable photobiocatalysis providing a sustainable solution for biomass processing.

scholarly journals A thermostable bacterial lytic polysaccharide monooxygenase with high operational stability in a wide temperature range

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Tina Rise Tuveng ◽  
Marianne Slang Jensen ◽  
Lasse Fredriksen ◽  
Gustav Vaaje-Kolstad ◽  
Vincent G. H. Eijsink ◽  
...  
Keyword(s):  
Wide Temperature Range ◽  
Plant Biomass ◽  
Thermostable Enzyme ◽  
Operational Stability ◽  
Lytic Polysaccharide Monooxygenase ◽  
Temperature Range ◽  
Catalytically Active ◽  
Polysaccharide Monooxygenases ◽  
Interesting Candidate ◽  
A Minor

Abstract Background Lytic polysaccharide monooxygenases (LPMOs) are oxidative, copper-dependent enzymes that function as powerful tools in the turnover of various biomasses, including lignocellulosic plant biomass. While LPMOs are considered to be of great importance for biorefineries, little is known about industrial relevant properties such as the ability to operate at high temperatures. Here, we describe a thermostable, cellulose-active LPMO from a high-temperature compost metagenome (called mgLPMO10). Results MgLPMO10 was found to have the highest apparent melting temperature (83 °C) reported for an LPMO to date, and is catalytically active up to temperatures of at least 80 °C. Generally, mgLPMO10 showed good activity and operational stability over a wide temperature range. The LPMO boosted cellulose saccharification by recombinantly produced GH48 and GH6 cellobiohydrolases derived from the same metagenome, albeit to a minor extent. Cellulose saccharification studies with a commercial cellulase cocktail (Celluclast®) showed that the performance of this thermostable bacterial LPMO is comparable with that of a frequently utilized fungal LPMO from Thermoascus aurantiacus (TaLPMO9A). Conclusions The high activity and operational stability of mgLPMO10 are of both fundamental and applied interest. The ability of mgLPMO10 to perform oxidative cleavage of cellulose at 80 °C and the clear synergy with Celluclast® make this enzyme an interesting candidate in the development of thermostable enzyme cocktails for use in lignocellulosic biorefineries.

scholarly journals Quantifying oxidation of cellulose-associated glucuronoxylan by two lytic polysaccharide monooxygenases from Neurospora crassa

2021 ◽  
Author(s):  
Olav A. Hegnar ◽  
Heidi Østby ◽  
Dejan M. Petrović ◽  
Lisbeth Olsson ◽  
Anikó Várnai ◽  
...  
Keyword(s):  
Neurospora Crassa ◽  
Plant Cell Wall ◽  
Plant Biomass ◽  
Hydrolytic Enzymes ◽  
Structural Features ◽  
Cell Wall Polysaccharides ◽  
Functional Variation ◽  
Lytic Polysaccharide Monooxygenases ◽  
Polysaccharide Monooxygenases ◽  
Oxidized Products

Family AA9 lytic polysaccharide monooxygenases (LPMOs) are abundant in fungi where they catalyze oxidative depolymerization of recalcitrant plant biomass. These AA9 LPMOs cleave cellulose, and some also act on hemicelluloses, primarily other (substituted) β-(1→4)-glucans. Oxidative cleavage of xylan has been shown for only a handful AA9 LPMOs, and it remains unclear whether this activity is a minor side reaction or primary function. Here, we show that Nc LPMO9F and the phylogenetically related, hitherto uncharacterized Nc LPMO9L from Neurospora crassa are active on both cellulose and cellulose-associated glucuronoxylan, but not on glucuronoxylan alone. A newly developed method for simultaneous quantification of xylan-derived and cellulose-derived oxidized products showed that Nc LPMO9F preferentially cleaves xylan when acting on a cellulose–beechwood glucuronoxylan mixture, yielding about three times more xylan-derived than cellulose-derived oxidized products. Interestingly, under similar conditions, Nc LPMO9L and previously characterized Mc LPMO9H from Malbranchea cinnamomea showed different xylan-to-cellulose preferences, giving oxidized product ratios of about 0.5:1 and 1:1, respectively, indicative of functional variation among xylan-active LPMOs. Phylogenetic and structural analysis of xylan-active AA9 LPMOs led to the identification of characteristic structural features, including unique features that do not occur in phylogenetically remote AA9 LPMOs, such as four AA9 LPMOs whose lack of activity towards glucuronoxylan was demonstrated in the present study. Taken together, the results provide a path towards discovery of additional xylan-active LPMOs and show that the huge family of AA9 LPMOs has members that preferentially act on xylan. These findings shed new light on the biological role and industrial potential of these fascinating enzymes. Importance Plant cell wall polysaccharides are highly resilient to depolymerization by hydrolytic enzymes, partly due to cellulose chains being tightly packed in microfibrils that are covered by hemicelluloses. Lytic polysaccharide monooxygenases (LPMOs) seem well suited to attack these resilient co-polymeric structures, but the occurrence and importance of hemicellulolytic activity among LPMOs remains unclear. Here we show that certain AA9 LPMOs preferentially cleave xylan when acting on a cellulose–glucuronoxylan mixture, and that this ability is the result of protein evolution that has resulted in a clade of AA9 LPMOs with specific structural features. Our findings strengthen the notion that the vast arsenal of AA9 LPMOs in certain fungal species provides functional versatility, and that AA9 LPMOs may have evolved to promote oxidative depolymerization of a wide variety of recalcitrant, co-polymeric plant polysaccharide structures. These findings have implications for understanding the biological roles and industrial potential of LPMOs.

scholarly journals Dissecting cellobiose metabolic pathway and its application in biorefinery through consolidated bioprocessing in Myceliophthora thermophila

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Jingen Li ◽  
Shuying Gu ◽  
Zhen Zhao ◽  
Bingchen Chen ◽  
Qian Liu ◽  
...  
Keyword(s):  
Malic Acid ◽  
Plant Biomass ◽  
Consolidated Bioprocessing ◽  
Cellulase Activity ◽  
Industrial Applications ◽  
Efficient Production ◽  
Myceliophthora Thermophila ◽  
Final Strain ◽  
Cellobiose Metabolism ◽  
Cost Efficient

Abstract Background Lignocellulosic biomass has long been recognized as a potential sustainable source for industrial applications. The costs associated with conversion of plant biomass to fermentable sugar represent a significant barrier to the production of cost-competitive biochemicals. Consolidated bioprocessing (CBP) is considered a potential breakthrough for achieving cost-efficient production of biomass-based fuels and commodity chemicals. During the degradation of cellulose, cellobiose (major end-product of cellulase activity) is catabolized by hydrolytic and phosphorolytic pathways in cellulolytic organisms. However, the details of the two intracellular cellobiose metabolism pathways in cellulolytic fungi remain to be uncovered. Results Using the engineered malic acid production fungal strain JG207, we demonstrated that the hydrolytic pathway by β-glucosidase and the phosphorolytic pathway by phosphorylase are both used for intracellular cellobiose metabolism in Myceliophthora thermophila, and the yield of malic acid can benefit from the energy advantages of phosphorolytic cleavage. There were obvious differences in regulation of the two cellobiose catabolic pathways depending on whether M. thermophila JG207 was grown on cellobiose or Avicel. Disruption of Mtcpp in strain JG207 led to decreased production of malic acid under cellobiose conditions, while expression levels of all three intracellular β-glucosidase genes were significantly up-regulated to rescue the impairment of the phosphorolytic pathway under Avicel conditions. When the flux of the hydrolytic pathway was reduced, we found that β-glucosidase encoded by bgl1 was the dominant enzyme in the hydrolytic pathway and deletion of bgl1 resulted in significant enhancement of protein secretion but reduction of malate production. Combining comprehensive manipulation of both cellobiose utilization pathways and enhancement of cellobiose uptake by overexpression of a cellobiose transporter, the final strain JG412Δbgl2Δbgl3 produced up to 101.2 g/L and 77.4 g/L malic acid from cellobiose and Avicel, respectively, which corresponded to respective yields of 1.35 g/g and 1.03 g/g, representing significant improvement over the starting strain JG207. Conclusions This is the first report of detailed investigation of intracellular cellobiose catabolism in cellulolytic fungus M. thermophila. These results provide insights that can be applied to industrial fungi for production of biofuels and biochemicals from cellobiose and cellulose.

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