scholarly journals Identification and Characterization of a Large Protein Essential for Degradation of the Crystalline Region of Cellulose by Cytophaga hutchinsonii

2016 ◽  
Vol 83 (1) ◽  
Author(s):  
Sen Wang ◽  
Dong Zhao ◽  
Xinfeng Bai ◽  
Weican Zhang ◽  
Xuemei Lu
Keyword(s):  
Cell Surface ◽  
Outer Surface ◽  
Deletion Mutant ◽  
Cellulose Degradation ◽  
Amorphous Region ◽  
Crystalline Cellulose ◽  
Crystalline Region ◽  
Content Type ◽  
Cytophaga Hutchinsonii ◽  
Unique Mechanism

ABSTRACT Cytophaga hutchinsonii is a Gram-negative bacterium that can efficiently degrade crystalline cellulose by a unique mechanism different from the free cellulase or cellulosome strategy. In this study, chu_3220, encoding the hypothetical protein CHU_3220 (205 kDa), was identified by insertional mutation and gene deletion as the first gene essential for degradation of the crystalline region but not the amorphous region of cellulose by C. hutchinsonii. A chu_3220 deletion mutant was defective in the degradation of crystalline cellulose and increased the degree of crystallinity of Avicel PH101 but could still degrade amorphous cellulose completely. CHU_3220 was found to be located on the outer surface of the outer membrane and could bind to cellulose. It contains 15 PbH1 domains and a C-terminal domain (CHU_C) that was proved to be critical for the localization of CHU_3220 on the cell surface and the function of CHU_3220 in crystalline cellulose degradation. Moreover, the degradation of crystalline cellulose was intact-cell dependent and inhibited by NaN3. Further study showed that chu_3220 was induced by cellulose and that the endoglucanase activity on the cell surface was significantly reduced without chu_3220. Real-time PCR revealed that the transcription of most genes encoding endoglucanases located on the cell surface was decreased in the chu_3220 deletion mutant, indicating that chu_3220 might also play a role in the regulation of the expression of some endoglucanases. IMPORTANCE Cytophaga hutchinsonii could efficiently degrade crystalline cellulose with a unique mechanism without cellulosomes and free cellulases. It lacks proteins that are thought to play important roles in disruption of the crystalline region of cellulose, including exoglucanases, lytic polysaccharide monooxygenases, expansins, expansin-like proteins, or swollenins, and most of its endoglucanases lack carbohydrate binding modules. The mechanism of the degradation of crystalline cellulose is still unknown. In this study, chu_3220 was identified as the first gene essential for the degradation of the crystalline region but not the amorphous region of cellulose. CHU_3220 is a high-molecular-weight protein located on the outer surface of the outer membrane and could bind to cellulose. We proposed that CHU_3220 might be an essential component of a protein complex on the cell surface in charge of the decrystallization of crystalline cellulose. The degradation of crystalline cellulose by C. hutchinsonii was not only dependent on intact cells but also required the energy supplied by the cells. This was obviously different from other known cellulose depolymerization system. Our study has shed more light on the novel strategy of crystalline cellulose degradation by C. hutchinsonii.

scholarly journals Periplasmic Cytophaga hutchinsonii Endoglucanases Are Required for Use of Crystalline Cellulose as the Sole Source of Carbon and Energy

2016 ◽  
Vol 82 (15) ◽  
pp. 4835-4845 ◽  
Author(s):  
Yongtao Zhu ◽  
Lanlan Han ◽  
Kathleen L. Hefferon ◽  
Nicholas R. Silvaggi ◽  
David B. Wilson ◽  
...  
Keyword(s):  
Cell Surface ◽  
Outer Membrane ◽  
Soluble Sugars ◽  
Surface Proteins ◽  
Cellulolytic Enzymes ◽  
Crystalline Cellulose ◽  
Cell Fractionation ◽  
Unknown Mechanism ◽  
Content Type ◽  
Cytophaga Hutchinsonii

ABSTRACTThe soil bacteriumCytophaga hutchinsoniiactively digests crystalline cellulose by a poorly understood mechanism. Genome analyses identified nine genes predicted to encode endoglucanases with roles in this process. No predicted cellobiohydrolases, which are usually involved in the utilization of crystalline cellulose, were identified. Chromosomal deletions were performed in eight of the endoglucanase-encoding genes:cel5A,cel5B,cel5C,cel9A,cel9B,cel9C,cel9E, andcel9F. Each mutant retained the ability to digest crystalline cellulose, although the deletion ofcel9Ccaused a modest decrease in cellulose utilization. Strains with multiple deletions were constructed to identify the critical cellulases. Cells of a mutant lacking bothcel5Bandcel9Cwere completely deficient in growth on cellulose. Cell fractionation and biochemical analyses indicate that Cel5B and Cel9C are periplasmic nonprocessive endoglucanases. The requirement of periplasmic endoglucanases for cellulose utilization suggests that cellodextrins are transported across the outer membrane during this process. Bioinformatic analyses predict that Cel5A, Cel9A, Cel9B, Cel9D, and Cel9E are secreted across the outer membrane by the type IX secretion system, which has been linked to cellulose utilization. These secreted endoglucanases may perform the initial digestion within amorphous regions on the cellulose fibers, releasing oligomers that are transported into the periplasm for further digestion by Cel5B and Cel9C. The results suggest that both cell surface and periplasmic endoglucanases are required for the growth ofC. hutchinsoniion cellulose and that novel cell surface proteins may solubilize and transport cellodextrins across the outer membrane.IMPORTANCEThe bacteriumCytophaga hutchinsoniidigests crystalline cellulose by an unknown mechanism. It lacks processive cellobiohydrolases that are often involved in cellulose digestion. Critical cellulolytic enzymes were identified by genetic analyses. Intracellular (periplasmic) nonprocessive endoglucanases performed an important role in cellulose utilization. The results suggest a model involving partial digestion at the cell surface, solubilization and uptake of cellodextrins across the outer membrane by an unknown mechanism, and further digestion within the periplasm. The ability to sequester cellodextrins and digest them intracellularly may limit losses of soluble cellobiose to other organisms.C. hutchinsoniiuses an unusual approach to digest cellulose and is a potential source of novel proteins to increase the efficiency of conversion of cellulose into soluble sugars and biofuels.

scholarly journals FLP-FRT-Based Method To Obtain Unmarked Deletions ofCHU_3237(porU) and Large Genomic Fragments of Cytophaga hutchinsonii

2014 ◽  
Vol 80 (19) ◽  
pp. 6037-6045 ◽  
Author(s):  
Ying Wang ◽  
Zhiquan Wang ◽  
Jing Cao ◽  
Zhiwei Guan ◽  
Xuemei Lu
Keyword(s):  
Cellulose Degradation ◽  
Degradation Mechanism ◽  
Signal Peptidase ◽  
Crystalline Cellulose ◽  
Cellulolytic Bacterium ◽  
Efficient Tool ◽  
Content Type ◽  
Cytophaga Hutchinsonii ◽  
Recombination System ◽  
Colony Spreading

ABSTRACTCytophaga hutchinsoniiis a widely distributed cellulolytic bacterium in the phylumBacteroidetes. It can digest crystalline cellulose rapidly without free cellulases or cellulosomes. The mechanism of its cellulose utilization remains a mystery. We developed an efficient method based on a linear DNA double-crossover and FLP-FRT recombination system to obtain unmarked deletions of both single genes and large genomic fragments inC. hutchinsonii. Unmarked deletion ofCHU_3237(porU), an ortholog of the C-terminal signal peptidase of a type IX secretion system (T9SS), resulted in defects in colony spreading, cellulose degradation, and protein secretion, indicating that it is a component of the T9SS and that T9SS plays an important role in cellulose degradation byC. hutchinsonii. Furthermore, deletions of four large genomic fragments were obtained using our method, and the sizes of the excised fragments varied from 9 to 19 kb, spanning from 6 to 22 genes. The customized FLP-FRT method provides an efficient tool for more rapid progress in the cellulose degradation mechanism and other physiological aspects ofC. hutchinsonii.

scholarly journals Novel Outer Membrane Protein Involved in Cellulose and Cellooligosaccharide Degradation by Cytophaga hutchinsonii

2014 ◽  
Vol 80 (15) ◽  
pp. 4511-4518 ◽  
Author(s):  
Xiaofei Ji ◽  
Ying Wang ◽  
Cong Zhang ◽  
Xinfeng Bai ◽  
Weican Zhang ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Cell Surface ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Cellulose Degradation ◽  
Outer Membrane Proteins ◽  
Cellulolytic Enzymes ◽  
Content Type ◽  
Cytophaga Hutchinsonii ◽  
Glucosidase Activity

ABSTRACTCytophaga hutchinsoniiis an aerobic cellulolytic soil bacterium which was reported to use a novel contact-dependent strategy to degrade cellulose. It was speculated that cellooligosaccharides were transported into the periplasm for further digestion. In this study, we reported that most of the endoglucanase and β-glucosidase activity was distributed on the cell surface ofC. hutchinsonii. Cellobiose and part of the cellulose could be hydrolyzed to glucose on the cell surface. However, the cell surface cellulolytic enzymes were not sufficient for cellulose degradation byC. hutchinsonii. An outer membrane protein, CHU_1277, was disrupted by insertional mutation. Although the mutant maintained the same endoglucanase activity and most of the β-glucosidase activity, it failed to digest cellulose, and its cellooligosaccharide utilization ability was significantly reduced, suggesting that CHU_1277 was essential for cellulose degradation and played an important role in cellooligosaccharide utilization. Further study of cellobiose hydrolytic ability of the mutant on the enzymatic level showed that the β-glucosidase activity in the outer membrane of the mutant was not changed. It revealed that CHU_1277 played an important role in assisting cell surface β-glucosidase to exhibit its activity sufficiently. Studies on the outer membrane proteins involved in cellulose and cellooligosaccharide utilization could shed light on the mechanism of cellulose degradation byC. hutchinsonii.

scholarly journals Cytophaga hutchinsonii gldN, Encoding a Core Component of the Type IX Secretion System, Is Essential for Ion Assimilation, Cellulose Degradation, and Cell Motility

2020 ◽  
Vol 86 (11) ◽  
Author(s):  
Lijuan Gao ◽  
Zhiwei Guan ◽  
Peng Gao ◽  
Weican Zhang ◽  
Qingsheng Qi ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Metal Ion ◽  
Cellulose Degradation ◽  
Secretion System ◽  
Crystalline Cellulose ◽  
Core Component ◽  
Content Type ◽  
Cytophaga Hutchinsonii ◽  
Growth Defects ◽  
Type Ix Secretion System

ABSTRACT The type IX secretion system (T9SS), which is involved in pathogenicity, motility, and utilization of complex biopolymers, is a novel protein secretion system confined to the phylum Bacteroidetes. Cytophaga hutchinsonii, a common cellulolytic soil bacterium belonging to the phylum Bacteroidetes, can rapidly digest crystalline cellulose using a novel strategy. In this study, the deletion mutant of chu_0174 (gldN) was obtained using PY6 medium supplemented with Stanier salts. GldN was verified to be a core component of C. hutchinsonii T9SS, and is indispensable for cellulose degradation, motility, and secretion of C-terminal domain (CTD) proteins. Notably, the ΔgldN mutant showed significant growth defects in Ca2+- and Mg2+-deficient media. These growth defects could be relieved by the addition of Ca2+ or Mg2+. The intracellular concentrations of Ca2+ and Mg2+ were markedly reduced in ΔgldN. These results demonstrated that GldN is essential for the acquisition of trace amounts of Ca2+ and Mg2+, especially for Ca2+. Moreover, an outer membrane efflux protein, CHU_2807, which was decreased in abundance on the outer membrane of ΔgldN, is essential for normal growth in PY6 medium. The reduced intracellular accumulation of Ca2+ and Mg2+ in the Δ2807 mutant indicated that CHU_2807 is involved in the uptake of trace amounts of Ca2+ and Mg2+. This study provides insights into the role of T9SS in metal ion assimilation in C. hutchinsonii. IMPORTANCE The widespread Gram-negative bacterium Cytophaga hutchinsonii uses a novel but poorly understood strategy to utilize crystalline cellulose. Recent studies showed that a T9SS exists in C. hutchinsonii and is involved in cellulose degradation and motility. However, the main components of the C. hutchinsonii T9SS and their functions are still unclear. Our study characterized the function of GldN, which is a core component of the T9SS. GldN was proved to play vital roles in cellulose degradation and cell motility. Notably, GldN is essential for the acquisition of Ca2+ and Mg2+ ions under Ca2+- and Mg2+-deficient conditions, revealing a link between the T9SS and the metal ion transport system. The outer membrane abundance of CHU_2807, which is essential for Ca2+ and Mg2+ uptake in PY6 medium, was affected by the deletion of GldN. This study demonstrated that the C. hutchinsonii T9SS has extensive functions, including cellulose degradation, motility, and metal ion assimilation, and contributes to further understanding of the function of the T9SS in the phylum Bacteroidetes.

scholarly journals A Disulfide Oxidoreductase (CHU_1165) Is Essential for Cellulose Degradation by Affecting Outer Membrane Proteins in Cytophaga hutchinsonii

2020 ◽  
Vol 86 (8) ◽  
Author(s):  
Dong Zhao ◽  
Ying Wang ◽  
Sen Wang ◽  
Weican Zhang ◽  
Qingsheng Qi ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Disulfide Bond ◽  
Cellulose Degradation ◽  
Outer Membrane Proteins ◽  
Hypothetical Protein ◽  
Pleiotropic Effect ◽  
Content Type ◽  
Cytophaga Hutchinsonii ◽  
Disulfide Oxidoreductase

ABSTRACT Cytophaga hutchinsonii cells can bind to the surface of insoluble cellulose and degrade it by utilizing a novel cell contact-dependent mechanism, in which the outer membrane proteins may play important roles. In this study, the deletion of a gene locus, chu_1165, which encodes a hypothetical protein with 32% identity with TlpB, a disulfide oxidoreductase in Flavobacterium psychrophilum, caused a complete cellulolytic defect in C. hutchinsonii. Further study showed that cells of the Δ1165 strain could not bind to cellulose, and the levels of many outer membrane proteins that can bind to cellulose were significantly decreased. The N-terminal region of CHU_1165 is anchored to the cytoplasmic membrane with five predicted transmembrane helices, and the C-terminal region is predicted to stretch to the periplasm and has a similar thioredoxin (Trx) fold containing a Cys-X-X-Cys motif that is conserved in disulfide oxidoreductases. Recombinant CHU_1165His containing the Cys-X-X-Cys motif was able to reduce the disulfide bonds of insulin in vitro. Site-directed mutation showed that the cysteines in the Cys-X-X-Cys motif and at residues 106 and 108 were indispensable for the function of CHU_1165. Western blotting showed that CHU_1165 was in an oxidized state in vivo, suggesting that it may act as an oxidase to catalyze disulfide bond formation. However, many of the decreased outer membrane proteins that were essential for cellulose degradation contained no or one cysteine, and mutation of the cysteine in these proteins did not affect cellulose degradation, indicating that CHU_1165 may have an indirect or pleiotropic effect on the function of these outer membrane proteins. IMPORTANCE Cytophaga hutchinsonii can rapidly digest cellulose in a contact-dependent manner, in which the outer membrane proteins may play important roles. In this study, a hypothetical protein, CHU_1165, characterized as a disulfide oxidoreductase, is essential for cellulose degradation by affecting the cellulose binding ability of many outer membrane proteins in C. hutchinsonii. Disulfide oxidoreductases are involved in disulfide bond formation. However, our studies show that many of the decreased outer membrane proteins that were essential for cellulose degradation contained no or one cysteine, and mutation of cysteine did not affect their function, indicating that CHU_1165 did not facilitate the formation of a disulfide bond in these proteins. It may have an indirect or pleiotropic effect on the function of these outer membrane proteins. Our study provides an orientation for exploring the proteins that assist in the appropriate conformation of many outer membrane proteins essential for cellulose degradation, which is important for exploring the novel mechanism of cellulose degradation in C. hutchinsonii.

scholarly journals Hypothetical Protein Avin_16040 as the S-Layer Protein of Azotobacter vinelandii and Its Involvement in Plant Root Surface Attachment

2015 ◽  
Vol 81 (21) ◽  
pp. 7484-7495 ◽  
Author(s):  
Pauline Woan Ying Liew ◽  
Bor Chyan Jong ◽  
Nazalan Najimudin
Keyword(s):  
Cell Surface ◽  
Deletion Mutant ◽  
Azotobacter Vinelandii ◽  
Plant Root ◽  
Hypothetical Protein ◽  
Surface Hydrophobicity ◽  
Root Surface ◽  
Bacterial Cells ◽  
Wild Type ◽  
Content Type

ABSTRACTA proteomic analysis of a soil-dwelling, plant growth-promotingAzotobacter vinelandiistrain showed the presence of a protein encoded by the hypotheticalAvin_16040gene when the bacterial cells were attached to theOryza sativaroot surface. AnAvin_16040deletion mutant demonstrated reduced cellular adherence to the root surface, surface hydrophobicity, and biofilm formation compared to those of the wild type. By atomic force microscopy (AFM) analysis of the cell surface topography, the deletion mutant displayed a cell surface architectural pattern that was different from that of the wild type.Escherichia colitransformed with the wild-typeAvin_16040gene displayed on its cell surface organized motifs which looked like the S-layer monomers ofA. vinelandii. The recombinantE. colialso demonstrated enhanced adhesion to the root surface.

scholarly journals An Outer Membrane Protein Involved in the Uptake of Glucose Is Essential for Cytophaga hutchinsonii Cellulose Utilization

2016 ◽  
Vol 82 (6) ◽  
pp. 1933-1944 ◽  
Author(s):  
Hong Zhou ◽  
Xia Wang ◽  
Tengteng Yang ◽  
Weixin Zhang ◽  
Guanjun Chen ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Cellulose Degradation ◽  
Expression Profiles ◽  
Transcriptional Profiling ◽  
Hydrolysis Product ◽  
Transcriptional Responses ◽  
Content Type ◽  
Cytophaga Hutchinsonii

ABSTRACTCytophaga hutchinsoniispecializes in cellulose digestion by employing a collection of novel cell-associated proteins. Here, we identified a novel gene locus, CHU_1276, that is essential forC. hutchinsoniicellulose utilization. Disruption of CHU_1276 inC. hutchinsoniiresulted in complete deficiency in cellulose degradation, as well as compromised assimilation of cellobiose or glucose at a low concentration. Further analysis showed that CHU_1276 was an outer membrane protein that could be induced by cellulose and low concentrations of glucose. Transcriptional profiling revealed that CHU_1276 exerted a profound effect on the genome-wide response to both glucose and Avicel and that the mutant lacking CHU_1276 displayed expression profiles very different from those of the wild-type strain under different culture conditions. Specifically, comparison of their transcriptional responses to cellulose led to the identification of a gene set potentially regulated by CHU_1276. These results suggest that CHU_1276 plays an essential role in cellulose utilization, probably by coordinating the extracellular hydrolysis of cellulose substrate with the intracellular uptake of the hydrolysis product inC. hutchinsonii.

A T9SS Substrate Involved in Crystalline Cellulose Degradation by Affecting Crucial Cellulose Binding Proteins in Cytophaga hutchinsonii

2021 ◽  
Author(s):  
Lijuan Gao ◽  
Yaru Su ◽  
Wenxia Song ◽  
Weican Zhang ◽  
Qingsheng Qi ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Gene Locus ◽  
Cellulose Degradation ◽  
Degradation Mechanism ◽  
Crystalline Cellulose ◽  
Cellulolytic Bacterium ◽  
Cytophaga Hutchinsonii ◽  
Surface Localization ◽  
Cell Surface Localization ◽  
Cellulose Binding

Cytophaga hutchinsonii is an abundant soil cellulolytic bacterium that uses a unique cellulose degradation mechanism different from those that involve free cellulases or cellulosomes. Though several proteins were identified to be important for cellulose degradation, the mechanism used by C. hutchinsonii to digest crystalline cellulose remains a mystery. In this study, chu_0922 was identified by insertional mutation and gene deletion as an important gene locus indispensable for crystalline cellulose utilization. Deletion of chu_0922 resulted in defect in crystalline cellulose utilization. The Δ 0922 mutant completely lost the ability to grow on crystalline cellulose even with extended incubation, and selectively utilized the amorphous region of cellulose leading to the increased crystallinity. As a protein secreted by the type Ⅸ secretion system (T9SS), CHU_0922 was found to be located on the outer membrane, and the outer membrane localization of CHU_0922 relied on the T9SS. Comparative analysis of the outer membrane proteins revealed that the abundance of several cellulose binding proteins, including CHU_1276, CHU_1277, and CHU_1279, was reduced in the Δ 0922 mutant. Further study showed that CHU_0922 is crucial for the full expression of the gene cluster containing chu_1276 , chu_1277 , chu_1278 , chu_1279 , and chu_1280 ( cel9C ), which is essential for cellulose utilization. Moreover, CHU_0922 is required for the cell surface localization of CHU_3220, a cellulose binding protein that is essential for crystalline cellulose utilization. Our study provides insights into the complex system that C. hutchinsonii uses to degrade crystalline cellulose. IMPORTANCE The widespread aerobic cellulolytic bacterium Cytophaga hutchinsonii , belonging to the phylum Bacteroidetes , utilizes a novel mechanism to degrade crystalline cellulose. No genes encoding proteins specialized in loosening or disruption the crystalline structure of cellulose were identified in the genome of C. hutchinsonii , except for chu_3220 and chu_1557 . The crystalline cellulose degradation mechanism remains enigmatic. This study identified a new gene locus, chu_0922 , encoding a typical T9SS substrate that is essential for crystalline cellulose degradation. Notably, CHU_0922 is crucial for the normal transcription of chu_1276 , chu_1277 , chu_1278 , chu_1279 , and chu_1280 ( cel9C ), which play important roles in the degradation of cellulose. Moreover, CHU_0922 participates in the cell surface localization of CHU_3220. These results demonstrated that CHU_0922 plays a key role in the crystalline cellulose degradation network. Our study will promote the uncovering of the novel cellulose utilization mechanism of C. hutchinsonii.

scholarly journals Inactivation of Cellobiose Dehydrogenases Modifies the Cellulose Degradation Mechanism of Podospora anserina

2016 ◽  
Vol 83 (2) ◽  
Author(s):  
Narumon Tangthirasunun ◽  
David Navarro ◽  
Sona Garajova ◽  
Didier Chevret ◽  
Laetitia Chan Ho Tong ◽  
...  
Keyword(s):  
Plant Biomass ◽  
Cellulose Degradation ◽  
Degradation Mechanism ◽  
Podospora Anserina ◽  
Cellulosic Biomass ◽  
Striking Difference ◽  
Crystalline Cellulose ◽  
Minor Role ◽  
Wild Type ◽  
Content Type

ABSTRACT Conversion of biomass into high-value products, including biofuels, is of great interest to developing sustainable biorefineries. Fungi are an inexhaustible source of enzymes to degrade plant biomass. Cellobiose dehydrogenases (CDHs) play an important role in the breakdown through synergistic action with fungal lytic polysaccharide monooxygenases (LPMOs). The three CDH genes of the model fungus Podospora anserina were inactivated, resulting in single and multiple CDH mutants. We detected almost no difference in growth and fertility of the mutants on various lignocellulose sources, except on crystalline cellulose, on which a 2-fold decrease in fertility of the mutants lacking P. anserina CDH1 (PaCDH1) and PaCDH2 was observed. A striking difference between wild-type and mutant secretomes was observed. The secretome of the mutant lacking all CDHs contained five beta-glucosidases, whereas the wild type had only one. P. anserina seems to compensate for the lack of CDH with secretion of beta-glucosidases. The addition of P. anserina LPMO to either the wild-type or mutant secretome resulted in improvement of cellulose degradation in both cases, suggesting that other redox partners present in the mutant secretome provided electrons to LPMOs. Overall, the data showed that oxidative degradation of cellulosic biomass relies on different types of mechanisms in fungi. IMPORTANCE Plant biomass degradation by fungi is a complex process involving dozens of enzymes. The roles of each enzyme or enzyme class are not fully understood, and utilization of a model amenable to genetic analysis should increase the comprehension of how fungi cope with highly recalcitrant biomass. Here, we report that the cellobiose dehydrogenases of the model fungus Podospora anserina enable it to consume crystalline cellulose yet seem to play a minor role on actual substrates, such as wood shavings or miscanthus. Analysis of secreted proteins suggests that Podospora anserina compensates for the lack of cellobiose dehydrogenase by increasing beta-glucosidase expression and using an alternate electron donor for LPMO.

scholarly journals Metabolic Engineering of Clostridium cellulolyticum for Production of Isobutanol from Cellulose

2011 ◽  
Vol 77 (8) ◽  
pp. 2727-2733 ◽  
Author(s):  
Wendy Higashide ◽  
Yongchao Li ◽  
Yunfeng Yang ◽  
James C. Liao
Keyword(s):  
Metabolic Engineering ◽  
Consolidated Bioprocessing ◽  
Cellulose Degradation ◽  
Crystalline Cellulose ◽  
Cellulolytic Activity ◽  
Keto Acid ◽  
Acid Biosynthesis ◽  
Content Type ◽  
Clostridium Cellulolyticum ◽  
Alcohol Synthesis

ABSTRACTProducing biofuels directly from cellulose, known as consolidated bioprocessing, is believed to reduce costs substantially compared to a process in which cellulose degradation and fermentation to fuel are accomplished in separate steps. Here we present a metabolic engineering example for the development of aClostridium cellulolyticumstrain for isobutanol synthesis directly from cellulose. This strategy exploits the host's natural cellulolytic activity and the amino acid biosynthesis pathway and diverts its 2-keto acid intermediates toward alcohol synthesis. Specifically, we have demonstrated the first production of isobutanol to approximately 660 mg/liter from crystalline cellulose by using this microorganism.

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