scholarly journals Cellulase-Xylanase Synergy in Designer Cellulosomes for Enhanced Degradation of a Complex Cellulosic Substrate

mBio ◽  
2010 ◽  
Vol 1 (5) ◽  
Author(s):  
Sarah Moraïs ◽  
Yoav Barak ◽  
Jonathan Caspi ◽  
Yitzhak Hadar ◽  
Raphael Lamed ◽  
...  
Keyword(s):  
Wheat Straw ◽  
Alternative Energy ◽  
Glycoside Hydrolases ◽  
Synergistic Activity ◽  
Molecular Architecture ◽  
Major Barrier ◽  
Content Type ◽  
Cellulosic Substrate ◽  
Combined Action ◽  
Designer Cellulosome

ABSTRACTDesigner cellulosomes are precision-engineered multienzyme complexes in which the molecular architecture and enzyme content are exquisitely controlled. This system was used to examine enzyme cooperation for improved synergy amongThermobifida fuscaglycoside hydrolases. TwoT. fuscacellulases, Cel48A exoglucanase and Cel5A endoglucanase, and twoT. fuscaxylanases, endoxylanases Xyn10B and Xyn11A, were selected as enzymatic components of a mixed cellulase/xylanase-containing designer cellulosome. The resultant mixed multienzyme complex was fabricated on a single scaffoldin subunit bearing all four enzymes. Conversion ofT. fuscaenzymes to the cellulosomal mode followed by their subsequent incorporation into a tetravalent cellulosome led to assemblies with enhanced activity (~2.4-fold) on wheat straw as a complex cellulosic substrate. The enhanced synergy was caused by the proximity of the enzymes on the complex compared to the free-enzyme systems. The hydrolytic properties of the tetravalent designer cellulosome were compared with the combined action of two separate divalent cellulase- and xylanase-containing cellulosomes. Significantly, the tetravalent designer cellulosome system exhibited an ~2-fold enhancement in enzymatic activity compared to the activity of the mixture of two distinct divalent scaffoldin-borne enzymes. These results provide additional evidence that close proximity between cellulases and xylanases is key to the observed concerted degradation of the complex cellulosic substrate in which the integrated enzymes complement each other by promoting access to the relevant polysaccharide components of the substrate. The data demonstrate that cooperation among xylanases and cellulases can be augmented by their integration into a single designer cellulosome.IMPORTANCEGlobal efforts towards alternative energy programs are highlighted by processes for converting plant-derived carbohydrates to biofuels. The major barrier in such processes is the inherent recalcitrance to enzymatic degradation of cellulose combined with related associated polysaccharides. The multienzyme cellulosome complexes, produced by anaerobic bacteria, are considered to be the most efficient systems for degradation of plant cell wall biomass. In the present work, we have employed a synthetic biology approach by producing artificial designer cellulosomes of predefined enzyme composition and architecture. The engineered tetravalent cellulosome complexes contain two different types of cellulases and two distinct xylanases. Using this approach, enhanced synergistic activity was observed on wheat straw, a natural recalcitrant substrate. The present work strives to gain insight into the combined action of cellulosomal enzyme components towards the development of advanced systems for improved degradation of cellulosic material.

scholarly journals Contribution of a Xylan-Binding Module to the Degradation of a Complex Cellulosic Substrate by Designer Cellulosomes

2010 ◽  
Vol 76 (12) ◽  
pp. 3787-3796 ◽  
Author(s):  
Sarah Moraïs ◽  
Yoav Barak ◽  
Jonathan Caspi ◽  
Yitzhak Hadar ◽  
Raphael Lamed ◽  
...  
Keyword(s):  
Wheat Straw ◽  
Plant Cell Wall ◽  
Proximity Effects ◽  
Synergistic Activity ◽  
Wild Type ◽  
Cellulosic Substrate ◽  
Specific Degradation ◽  
Designer Cellulosome ◽  
Insight Into ◽  
Enhance Activity

ABSTRACT Conversion of components of the Thermobifida fusca free-enzyme system to the cellulosomal mode using the designer cellulosome approach can be employed to discover the properties and inherent advantages of the cellulosome system. In this article, we describe the conversion of the T. fusca xylanases Xyn11A and Xyn10B and their synergistic interaction in the free state or within designer cellulosome complexes in order to enhance specific degradation of hatched wheat straw as a model for a complex cellulosic substrate. Endoglucanase Cel5A from the same bacterium and its recombinant dockerin-containing chimera were also studied for their combined effect, together with the xylanases, on straw degradation. Synergism was demonstrated when Xyn11A was combined with Xyn10B and/or Cel5A, and ∼1.5-fold activity enhancements were achieved by the designer cellulosome complexes compared to the free wild-type enzymes. These improvements in activity were due to both substrate-targeting and proximity effects among the enzymes contained in the designer cellulosome complexes. The intrinsic cellulose/xylan-binding module (XBM) of Xyn11A appeared to be essential for efficient substrate degradation. Indeed, only designer cellulosomes in which the XBM was maintained as a component of Xyn11A achieved marked enhancement in activity compared to the combination of wild-type enzymes. Moreover, integration of the XBM in designer cellulosomes via a dockerin module (separate from the Xyn11A catalytic module) failed to enhance activity, suggesting a role in orienting the parent xylanase toward its preferred polysaccharide component of the complex wheat straw substrate. The results provide novel mechanistic insight into the synergistic activity of designer cellulosome components on natural plant cell wall substrates.

scholarly journals Assembly of Xylanases into Designer Cellulosomes Promotes Efficient Hydrolysis of the Xylan Component of a Natural Recalcitrant Cellulosic Substrate

mBio ◽  
2011 ◽  
Vol 2 (6) ◽  
Author(s):  
Sarah Moraïs ◽  
Yoav Barak ◽  
Yitzhak Hadar ◽  
David B. Wilson ◽  
Yuval Shoham ◽  
...  
Keyword(s):  
Cell Wall ◽  
Wheat Straw ◽  
Enzymatic Degradation ◽  
Plant Cell Wall ◽  
Anaerobic Bacteria ◽  
Synergistic Action ◽  
Cellulosic Biomass ◽  
Thermobifida Fusca ◽  
Content Type ◽  
Designer Cellulosome

ABSTRACTIn nature, the complex composition and structure of the plant cell wall pose a barrier to enzymatic degradation. Nevertheless, some anaerobic bacteria have evolved for this purpose an intriguing, highly efficient multienzyme complex, the cellulosome, which contains numerous cellulases and hemicellulases. The rod-like cellulose component of the plant cell wall is embedded in a colloidal blend of hemicelluloses, a major component of which is xylan. In order to enhance enzymatic degradation of the xylan component of a natural complex substrate (wheat straw) and to study the synergistic action among different xylanases, we have employed a variation of the designer cellulosome approach by fabricating a tetravalent complex that includes the three endoxylanases ofThermobifida fusca(Xyn10A, Xyn10B, and Xyn11A) and an Xyl43A β-xylosidase from the same bacterium. Here, we describe the conversion of Xyn10A and Xyl43A to the cellulosomal mode. The incorporation of the Xyl43A enzyme together with the three endoxylanases into a common designer cellulosome served to enhance the level of reducing sugars produced during wheat straw degradation. The enhanced synergistic action of the four xylanases reflected their immediate juxtaposition in the complex, and these tetravalent xylanolytic designer cellulosomes succeeded in degrading significant (~25%) levels of the total xylan component of the wheat straw substrate. The results suggest that the incorporation of xylanases into cellulosome complexes is advantageous for efficient decomposition of recalcitrant cellulosic substrates—a distinction previously reserved for cellulose-degrading enzymes.IMPORTANCEXylanases are important enzymes for our society, due to their variety of industrial applications. Together with cellulases and other glycoside hydrolases, xylanases may also provide cost-effective conversion of plant-derived cellulosic biomass into soluble sugars en route to biofuels as an alternative to fossil fuels. Xylanases are commonly found in multienzyme cellulosome complexes, produced by anaerobic bacteria, which are considered to be among the most efficient systems for degradation of cellulosic biomass. Using a designer cellulosome approach, we have incorporated the entire xylanolytic system of the bacteriumThermobifida fuscainto defined artificial cellulosome complexes. The combined action of these designer cellulosomes versus that of the wild-type free xylanase system was then compared. Our data demonstrated that xylanolytic designer cellulosomes displayed enhanced synergistic activities on a natural recalcitrant wheat straw substrate and could thus serve in the development of advanced systems for improved degradation of lignocellulosic material.

scholarly journals Establishment of a Simple Lactobacillus plantarum Cell Consortium for Cellulase-Xylanase Synergistic Interactions

2013 ◽  
Vol 79 (17) ◽  
pp. 5242-5249 ◽  
Author(s):  
Sarah Moraïs ◽  
Naama Shterzer ◽  
Inna Rozman Grinberg ◽  
Geir Mathiesen ◽  
Vincent G. H. Eijsink ◽  
...  
Keyword(s):  
Wheat Straw ◽  
Lactobacillus Plantarum ◽  
Plant Biomass ◽  
Soluble Sugar ◽  
Acid Tolerance ◽  
Cellulolytic Bacterium ◽  
Synergistic Activity ◽  
Heterologous Proteins ◽  
Content Type ◽  
Highly Active

ABSTRACTLactobacillus plantarumis an attractive candidate for bioprocessing of lignocellulosic biomass due to its high metabolic variability, including its ability to ferment both pentoses and hexoses, as well as its high acid tolerance, a quality often utilized in industrial processes. This bacterium grows naturally on biomass; however, it lacks the inherent ability to deconstruct lignocellulosic substrates. As a first step toward engineering lignocellulose-converting lactobacilli, we have introduced genes coding for a GH6 cellulase and a GH11 xylanase from a highly active cellulolytic bacterium intoL. plantarum. For this purpose, we employed the recently developed pSIP vectors for efficient secretion of heterologous proteins. Both enzymes were secreted byL. plantarumat levels estimated at 0.33 nM and 3.3 nM, for the cellulase and xylanase, respectively, in culture at an optical density at 600 nm (OD600) of 1. Transformed cells demonstrated the ability to degrade individually either cellulose or xylan and wheat straw. When mixed together to form a two-strain cell-based consortium secreting both cellulase and xylanase, they exhibited synergistic activity in the overall release of soluble sugar from wheat straw. This result paves the way toward metabolic harnessing ofL. plantarumfor novel biorefining applications, such as production of ethanol and polylactic acid directly from plant biomass.

scholarly journals Deconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes

mBio ◽  
2012 ◽  
Vol 3 (6) ◽  
Author(s):  
Sarah Moraïs ◽  
Ely Morag ◽  
Yoav Barak ◽  
Dan Goldman ◽  
Yitzhak Hadar ◽  
...  
Keyword(s):  
Wheat Straw ◽  
Plant Cell Wall ◽  
Soluble Sugar ◽  
Cellulosic Biomass ◽  
Thermobifida Fusca ◽  
Cellulolytic Bacterium ◽  
Artificial Enzyme ◽  
Wild Type ◽  
Content Type ◽  
Designer Cellulosome

ABSTRACTLignocellulosic biomass, the most abundant polymer on Earth, is typically composed of three major constituents: cellulose, hemicellulose, and lignin. The crystallinity of cellulose, hydrophobicity of lignin, and encapsulation of cellulose by the lignin-hemicellulose matrix are three major factors that contribute to the observed recalcitrance of lignocellulose. By means of designer cellulosome technology, we can overcome the recalcitrant properties of lignocellulosic substrates and thus increase the level of native enzymatic degradation. In this context, we have integrated six dockerin-bearing cellulases and xylanases from the highly cellulolytic bacterium,Thermobifida fusca, into a chimeric scaffoldin engineered to bear a cellulose-binding module and the appropriate matching cohesin modules. The resultant hexavalent designer cellulosome represents the most elaborate artificial enzyme composite yet constructed, and the fully functional complex achieved enhanced levels (up to 1.6-fold) of degradation of untreated wheat straw compared to those of the wild-type free enzymes. The action of these designer cellulosomes on wheat straw was 33 to 42% as efficient as the natural cellulosomes ofClostridium thermocellum. In contrast, the reduction of substrate complexity by chemical or biological pretreatment of the substrate removed the advantage of the designer cellulosomes, as the free enzymes displayed higher levels of activity, indicating that enzyme proximity between these selected enzymes was less significant on pretreated substrates. Pretreatment of the substrate caused an increase in activity for all the systems, and the native cellulosome completely converted the substrate into soluble saccharides.IMPORTANCECellulosic biomass is a potential alternative resource which could satisfy future demands of transportation fuel. However, overcoming the natural lignocellulose recalcitrance remains challenging. Current research and development efforts have concentrated on the efficient cellulose-degrading strategies of cellulosome-producing anaerobic bacteria. Cellulosomes are multienzyme complexes capable of converting the plant cell wall polysaccharides into soluble sugar products en route to biofuels as an alternative to fossil fuels. Using a designer cellulosome approach, we have constructed the largest form of homogeneous artificial cellulosomes reported to date, which bear a total of six different cellulases and xylanases from the highly cellulolytic bacteriumThermobifida fusca. These designer cellulosomes were comparable in size to natural cellulosomes and displayed enhanced synergistic activities compared to their free wild-type enzyme counterparts. Future efforts should be invested to improve these processes to approach or surpass the efficiency of natural cellulosomes for cost-effective production of biofuels.

scholarly journals Glycoside Hydrolases Degrade Polymicrobial Bacterial Biofilms in Wounds

2016 ◽  
Vol 61 (2) ◽  
Author(s):  
Derek Fleming ◽  
Laura Chahin ◽  
Kendra Rumbaugh
Keyword(s):  
Glycoside Hydrolase ◽  
Bacterial Population ◽  
Chronic Wounds ◽  
Glycoside Hydrolases ◽  
Bacterial Biofilms ◽  
Planktonic Cells ◽  
Content Type ◽  
Biomass Dissolution

ABSTRACT The persistent nature of chronic wounds leaves them highly susceptible to invasion by a variety of pathogens that have the ability to construct an extracellular polymeric substance (EPS). This EPS makes the bacterial population, or biofilm, up to 1,000-fold more antibiotic tolerant than planktonic cells and makes wound healing extremely difficult. Thus, compounds which have the ability to degrade biofilms, but not host tissue components, are highly sought after for clinical applications. In this study, we examined the efficacy of two glycoside hydrolases, α-amylase and cellulase, which break down complex polysaccharides, to effectively disrupt Staphylococcus aureus and Pseudomonas aeruginosa monoculture and coculture biofilms. We hypothesized that glycoside hydrolase therapy would significantly reduce EPS biomass and convert bacteria to their planktonic state, leaving them more susceptible to conventional antimicrobials. Treatment of S. aureus and P. aeruginosa biofilms, grown in vitro and in vivo, with solutions of α-amylase and cellulase resulted in significant reductions in biomass, dissolution of the biofilm, and an increase in the effectiveness of subsequent antibiotic treatments. These data suggest that glycoside hydrolase therapy represents a potential safe, effective, and new avenue of treatment for biofilm-related infections.

Problems of adoption of solar power and subsequent switching behavior: an exploration in India

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Subhadip Roy ◽  
Subhalaxmi Mohapatra
Keyword(s):  
Behavioral Intentions ◽  
Structural Equation ◽  
Alternative Energy ◽  
Solar Power ◽  
Switching Behavior ◽  
Energy Sources ◽  
Energy Usage ◽  
Content Type ◽  
Household Level ◽  
Alternative Energy Sources

Purpose The challenges and factors of household adoption and the use of alternative energy sources have been a point of discussion among researchers. The purpose of this study is to apply a variant of the unified theory of adoption and use of technology (i.e. UTAUT 2) to explore the effect of various constructs that influence technology adoption on the consumers’ intention to adopt (and use) solar power generators (SPG) at the household level and the subsequent switching behavior. Design/methodology/approach Based on survey data collected from six cities in India (n = 1,246), factor analysis and structural equation modeling are applied for data analysis and testing the study hypotheses. Findings The results of the structural equation model found UTAUT constructs performance expectancy, effort expectancy, social influence and hedonic to positively affect behavioral intentions to adopt SPG. However, facilitating conditions and perceived value was not found to affect behavioral intentions to adopt SPG. Behavioral intentions to adopt SPG was found to positively influence the switching behavior. Research limitations/implications The present study augments the domain of alternative energy usage behavior by applying the UTAUT 2 in the adoption of alternative energy sources (namely, solar) and subsequent switching behavior from traditional sources at the household level. Practical implications The findings from the present study will guide the marketers and policymakers on the consumer attitudinal and behavioral aspects of solar energy usage at the household level and subsequent switching behavior. Originality/value The present study is novel as it moves beyond household-level behavioral intention to use solar energy and includes the switching behavior to shift to solar power from traditional energy sources.

Is it attractive to invest in alternative energy? Evidence from a five-factor Fama-French model for regional DJSI and renewable stock indexes

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Antonio Garcia-Amate ◽  
Alicia Ramírez-Orellana ◽  
Alfonso A. Rojo Ramirez
Keyword(s):  
Renewable Energy ◽  
Alternative Energy ◽  
Factor Model ◽  
Five Factor Model ◽  
Private Investment ◽  
Ordinary Least Squares ◽  
Green Economy ◽  
Economic Implications ◽  
Content Type ◽  
Thomson Reuters

PurposeThis study aims to examine the attractiveness of the regional Dow Jones Sustainability Indexes (DJSI) and several renewable energy indexes during December 31, 2010 to December 31, 2019. This study uses a risk-return analysis and a set of explanatory factors. Lastly, this study conducts a comparative analysis of these indexes with conventional indexes. Design/methodology/approachThis study uses data from Eikon, a Thomson Reuters database. To analyze the indexes’ behavior, this study uses the indexes’ annual return as of December 31 for each year. Next, this study estimates the Fama and French’s five-factor model using an ordinary least squares regression for regional DJSI and renewable energy indexes. FindingsThe results show that regional DJSIs delivered returns both above and below conventional indexes. In contrast, renewable energy indexes had high betas and negative returns, making them unattractive to investors. Practical implicationsThe results imply the need for public financing programs that support the transition to a sustainable economy and reduce risk and increase the return on private investment. Social implicationsThis study provides insights for policymakers regarding the importance of sustainability indexes in the transition to a green economy. Originality/valueThis study contributes to the growing literature on Fama and French’s five-factor model of sustainability indexes, especially in the current context characterized by intense green political changes. In particular, this study complements the few studies that have addressed the economic implications of renewable energy indexes in markets.

scholarly journals Efficient Plant Biomass Degradation by Thermophilic Fungus Myceliophthora heterothallica

2012 ◽  
Vol 79 (4) ◽  
pp. 1316-1324 ◽  
Author(s):  
Joost van den Brink ◽  
Gonny C. J. van Muiswinkel ◽  
Bart Theelen ◽  
Sandra W. A. Hinz ◽  
Ronald P. de Vries
Keyword(s):  
Wheat Straw ◽  
Plant Biomass ◽  
Hydrolytic Enzymes ◽  
Reaction Times ◽  
Giant Reed ◽  
Thermophilic Fungi ◽  
Biomass Degradation ◽  
Thermostable Enzymes ◽  
Content Type

ABSTRACTRapid and efficient enzymatic degradation of plant biomass into fermentable sugars is a major challenge for the sustainable production of biochemicals and biofuels. Enzymes that are more thermostable (up to 70°C) use shorter reaction times for the complete saccharification of plant polysaccharides compared to hydrolytic enzymes of mesophilic fungi such asTrichodermaandAspergillusspecies. The genusMyceliophthoracontains four thermophilic fungi producing industrially relevant thermostable enzymes. Within this genus, isolates belonging toM. heterothallicawere recently separated from the well-described speciesM. thermophila. We evaluate here the potential ofM. heterothallicaisolates to produce efficient enzyme mixtures for biomass degradation. Compared to the other thermophilicMyceliophthoraspecies, isolates belonging toM. heterothallicaandM. thermophilagrew faster on pretreated spruce, wheat straw, and giant reed. According to their protein profiles andin vitroassays after growth on wheat straw, (hemi-)cellulolytic activities differed strongly betweenM. thermophilaandM. heterothallicaisolates. Compared toM. thermophila,M. heterothallicaisolates were better in releasing sugars from mildly pretreated wheat straw (with 5% HCl) with a high content of xylan. The high levels of residual xylobiose revealed that enzyme mixtures ofMyceliophthoraspecies lack sufficient β-xylosidase activity. Sexual crossing of twoM. heterothallicashowed that progenies had a large genetic and physiological diversity. In the future, this will allow further improvement of the plant biomass-degrading enzyme mixtures ofM. heterothallica.

How useful are smartphones for learning? Perceptions and practices of Library and Information Science students from Hong Kong and Japan

2015 ◽  
Vol 33 (4) ◽  
pp. 545-561 ◽  
Author(s):  
Zvjezdana Dukic ◽  
Dickson K.W. Chiu ◽  
Patrick Lo
Keyword(s):  
Hong Kong ◽  
Information Needs ◽  
Information Science ◽  
Academic Learning ◽  
Library And Information Science ◽  
Theory Approach ◽  
Convenience Sample ◽  
Major Barrier ◽  
Content Type ◽  
Actual Use

Purpose – The purpose of this paper is to provide an overview of higher education students’ experiences in using smartphones for learning purposes, and their perceptions of the suitability of smartphones for learning. Design/methodology/approach – A qualitative research method is applied to data collection and analysis by following the grounded theory approach. Data were gathered by an online focus group involving Library and Information Science (LIS) students from University of Hong Kong and University of Tsukuba (Japan). Findings – LIS students at both universities regularly use smartphones for communication, socializing, entertainment and other daily information needs. The findings show that LIS students commonly use smartphones for learning and consider smartphones to be very useful for their academic work. They use smartphones to access course materials, search library catalog, discuss course assignments with peers, take notes, etc. Although both academic libraries involved offer a variety of services for mobile devices, these services are still not used frequently. A major barrier to using smartphone for academic learning is the smartphone’s small screen. Research limitations/implications – The study relies on a convenience sample, restricted to students from two universities, one from Hong Kong and the other from Japan. Further research on a larger sample is recommended. Originality/value – The study adds to the knowledge of smartphone actual use for learning purposes and provides study participants’ insights on the usefulness of smartphones for learning.

scholarly journals Semimechanistic Pharmacokinetic/Pharmacodynamic Modeling of Fosfomycin and Sulbactam Combination against Carbapenem-Resistant Acinetobacter baumannii

2021 ◽  
Vol 65 (5) ◽  
Author(s):  
Sazlyna Mohd Sazlly Lim ◽  
Aaron J. Heffernan ◽  
Jason A. Roberts ◽  
Fekade B. Sime
Keyword(s):  
Acinetobacter Baumannii ◽  
Treatment Options ◽  
Pharmacodynamic Modeling ◽  
Synergistic Activity ◽  
Bacterial Burden ◽  
Target Attainment ◽  
Content Type ◽  
Carbapenem Resistant ◽  
Time Kill

ABSTRACT Due to limited treatment options for carbapenem-resistant Acinetobacter baumannii (CR-AB) infections, antibiotic combinations are now considered potential treatments for CR-AB. This study aimed to explore the utility of fosfomycin-sulbactam combination (FOS/SUL) therapy against CR-AB isolates. Synergism of FOS/SUL against 50 clinical CR-AB isolates was screened using the checkerboard method. Thereafter, time-kill studies against two CR-AB isolates were performed. The time-kill data were described using a semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model. Monte Carlo simulations were then performed to estimate the probability of stasis, 1-log kill, and 2-log kill after 24 h of combination therapy. The FOS/SUL combination demonstrated a synergistic effect against 74% of isolates. No antagonism was observed. The MIC50 and MIC90 of FOS/SUL were decreased 4- to 8-fold, compared to the monotherapy MIC50 and MIC90. In the time-kill studies, the combination displayed bactericidal activity against both isolates and synergistic activity against one isolate at the highest clinically achievable concentrations. Our PK/PD model was able to describe the interaction between fosfomycin and sulbactam in vitro. Bacterial kill was mainly driven by sulbactam, with fosfomycin augmentation. FOS/SUL regimens that included sulbactam at 4 g every 8 h demonstrated a probability of target attainment of 1-log10 kill at 24 h of ∼69 to 76%, compared to ∼15 to 30% with monotherapy regimens at the highest doses. The reduction in the MIC values and the achievement of a moderate PTA of a 2-log10 reduction in bacterial burden demonstrated that FOS/SUL may potentially be effective against some CR-AB infections.

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