Effect of pretreatment of hydrothermally processed rice straw with laccase-displaying yeast on ethanol fermentation

Ergosterol and Its Metabolites Induce Ligninolytic Activity in the Lignin-Degrading Fungus Phanerochaete sordida YK-624

White-rot fungi are the most important group of lignin biodegraders. Phanerochaete sordida YK-624 has higher ligninolytic activity than that of model white-rot fungi. However, the underlying mechanism responsible for lignin degradation by white-rot fungi remains unknown, and the induced compounds isolated from white-rot fungi for lignin degradation have never been studied. In the present study, we tried to screen ligninolytic-inducing compounds produced by P. sordida YK-624. After large-scale incubation of P. sordida YK-624, the culture and mycelium were separated by filtration. After the separation and purification, purified compounds were analyzed by high-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance. The sterilized unbleached hardwood kraft pulp was used for the initial evaluation of ligninolytic activity. Ergosterol was isolated and identified and it induced the lignin-degrading activity of this fungus. Moreover, we investigated ergosterol metabolites from P. sordida YK-624, and the ergosterol metabolites ergosta-4,7,22-triene-3,6-dione and ergosta-4,6,8(14),22-tetraen-3-one were identified and then chemically synthesized. These compounds significantly improved the lignin-degrading activity of the fungus. This is the first report on the ligninolytic-inducing compounds produced by white-rot fungi.

Laccase mediated delignification of wasted and non-food agricultural biomass: Recent developments and challenges

Utilization of microbial laccases is considered as the cleaner and target specific biocatalytic mechanism for the recovery of cellulose and hemicelluloses from nonfood and wasted agricultural, lignocellulosic biomass (LCB). The extent of lignin removal by laccase depends on the biochemical composition of biomass and the redox potential (E⁰) of the biocatalyst. Intensive research efforts are going on all over the world for the recognition of appropriate and easily available agricultural lignocellulosic feedstocks to exploit maximally for the production of value-added bioproducts and biofuels. In such circumstances, laccase can play a major role as a leading biocatalyst and potent substitute for chemical based deconstruction of the lignocellulosic materials. The limited commercialization of laccase at an industrial scale has been feasible due to its full working efficiency mostly expressed in the presence of cost intensive redox mediators only. Although, recently there are some reports that came on the mediator free biocatalysis of enzyme but still not considerably explored and neither understood in depth. The present review will address the various research gaps and shortcomings that acted as the big hurdles before the complete exploitation of laccases at an industrial scale. Further, this article also reveals insights on different microbial laccases and their diverse functional environmental conditions that affect the deconstruction process of LCB.

Development of Targeted Protein-Displaying Technology with a Novel Carbon Material

This study reports a new carbon material and its specific display of targeted protein. The properties of the carbon materials fabricated with carbon black MOGUL^® were analyzed. The carbon materials were spherical structures with 55.421 µm as a median value. The specific surface area, pore volume, average pore diameter, and total of the acidic functional group were 130 m²·g^-1, 0.55 cm³·g^-1, 17.2 nm, and 0.29 mEq·g^-1, respectively. The adsorption-desorption isoform of the carbon materials showed type IV of the hysteresis loop as defined by IUPAC, indicating non-uniform mesoporous structures (2-50 nm). The distribution of the log differential pore volume also indicated non-uniform porous structures because (i) the difference between the average pore size and the most frequent pore size was significant and (ii) the σ value was larger than the average value regarding the pore sizes. However, 10-90% of the integrated values of the log differential pore volume were 57.4% of the total integrated values, and the distribution was similar to the Gauss distribution model. Although the value of the total of the acidic functional group was 2.5-5.4 times lower than the values of the HPLC columns, the carbon materials require good scaffold quality rather than good HPLC quality. Therefore, the amounts could be enough for the scaffold of biotin hydrazide. To demonstrate the property of displaying the targeted proteins, carbon materials displaying biotin hydrazide by covalent bonding were prepared and avidin-labeled horse radish peroxidase (HRP) was bound to the biotin region. The carbon materials were porous structures, so the unspecific adsorption of HRP was estimated. Then, the maintenance ratios of HRP activities were analyzed in the repeated-use-with-wash processes after each evaluation, resulting in the activities of HRP on the carbon materials being treated with biotin hydrazide being significantly maintained compared to that of the ones without biotin hydrazide. The study revealed the properties of the carbon materials and indicated the display of HRP, suggesting that the carbon materials could be a new material for displaying targeted proteins.

Genome-based engineering of ligninolytic enzymes in fungi

Background

Many fungi grow as saprobic organisms and obtain nutrients from a wide range of dead organic materials. Among saprobes, fungal species that grow on wood or in polluted environments have evolved prolific mechanisms for the production of degrading compounds, such as ligninolytic enzymes. These enzymes include arrays of intense redox-potential oxidoreductase, such as laccase, catalase, and peroxidases. The ability to produce ligninolytic enzymes makes a variety of fungal species suitable for application in many industries, including the production of biofuels and antibiotics, bioremediation, and biomedical application as biosensors. However, fungal ligninolytic enzymes are produced naturally in small quantities that may not meet the industrial or market demands. Over the last decade, combined synthetic biology and computational designs have yielded significant results in enhancing the synthesis of natural compounds in fungi.

Main body of the abstract

In this review, we gave insights into different protein engineering methods, including rational, semi-rational, and directed evolution approaches that have been employed to enhance the production of some important ligninolytic enzymes in fungi. We described the role of metabolic pathway engineering to optimize the synthesis of chemical compounds of interest in various fields. We highlighted synthetic biology novel techniques for biosynthetic gene cluster (BGC) activation in fungo and heterologous reconstruction of BGC in microbial cells. We also discussed in detail some recombinant ligninolytic enzymes that have been successfully enhanced and expressed in different heterologous hosts. Finally, we described recent advance in CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-Cas (CRISPR associated) protein systems as the most promising biotechnology for large-scale production of ligninolytic enzymes.

Short conclusion

Aggregation, expression, and regulation of ligninolytic enzymes in fungi require very complex procedures with many interfering factors. Synthetic and computational biology strategies, as explained in this review, are powerful tools that can be combined to solve these puzzles. These integrated strategies can lead to the production of enzymes with special abilities, such as wide substrate specifications, thermo-stability, tolerance to long time storage, and stability in different substrate conditions, such as pH and nutrients.

Cell-surface engineering of yeasts for whole-cell biocatalysts

Due to the unique advantages comparing with traditional free enzymes and chemical catalysis, whole-cell biocatalysts have been widely used to catalyze reactions effectively, simply and environment friendly. Cell-surface display technology provides a novel and effective approach for improved whole-cell biocatalysts expressing heterologous enzymes on the cell surface. They can overcome the substrate transport limitation of the intracellular expression and provide the enzymes with enhanced properties. Among all the host surface-displaying microorganisms, yeast is ideally suitable for constructing whole cell-surface-displaying biocatalyst, because of the large cell size, the generally regarded as safe (GRAS) status, and the perfect post-translational processing of secreted proteins. Yeast cell-surface display system has been a promising and powerful method for development of novel and improved engineered biocatalysts. In this review, the characterization and principles of yeast cell-surface display and the applications of yeast cell-surface display in engineered whole-cell biocatalysts as well as the improvement of the enzyme efficiency are summarized and discussed.

Surface Display—An Alternative to Classic Enzyme Immobilization

Enzyme immobilization to solid matrices often presents a challenge due to protein conformation sensitivity, desired enzyme purity, and requirements for the particular carrier properties and immobilization technique. Surface display of enzymes at the cell walls of microorganisms presents an alternative that has been the focus of many research groups worldwide in different fields, such as biotechnology, energetics, pharmacology, medicine, and food technology. The range of systems by which a heterologous protein can be displayed at the cell surface allows the appropriate one to be found for almost every case. However, the efficiency of display systems is still quite low. The most frequently used yeast for the surface display of proteins is Saccharomyces cerevisiae. However, apart from its many advantages, Saccharomyces cerevisiae has some disadvantages, such as low robustness in industrial applications, hyperglycosylation of some heterologous proteins, and relatively low efficiency of surface display. Thus, in the recent years the display systems for alternative yeast hosts with better performances including Pichia pastoris, Hansenula polymorpha, Blastobotrys adeninivorans, Yarrowia lipolytica, Kluyveromyces marxianus, and others have been developed. Different strategies of surface display aimed to increase the amount of displayed protein, including new anchoring systems and new yeast hosts are reviewed in this paper.

The Role of Yeast-Surface-Display Techniques in Creating Biocatalysts for Consolidated BioProcessing

Climate change is directly linked to the rapid depletion of our non-renewable fossil resources and has posed concerns on sustainability. Thus, imploring the need for us to shift from our fossil based economy to a sustainable bioeconomy centered on biomass utilization. The efficient bioconversion of lignocellulosic biomass (an ideal feedstock) to a platform chemical, such as bioethanol, can be achieved via the consolidated bioprocessing technology, termed yeast surface engineering, to produce yeasts that are capable of this feat. This approach has various strategies that involve the display of enzymes on the surface of yeast to degrade the lignocellulosic biomass, then metabolically convert the degraded sugars directly into ethanol, thus elevating the status of yeast from an immobilization material to a whole-cell biocatalyst. The performance of the engineered strains developed from these strategies are presented, visualized, and compared in this article to highlight the role of this technology in moving forward to our quest against climate change. Furthermore, the qualitative assessment synthesized in this work can serve as a reference material on addressing the areas of improvement of the field and on assessing the capability and potential of the different yeast surface display strategies on the efficient degradation, utilization, and ethanol production from lignocellulosic biomass.

Yeast Hosts for the Production of Recombinant Laccases: A Review

Laccases are multi-copper oxidoreductases which catalyze the oxidation of a wide range of substrates during the simultaneous reduction of oxygen to water. These enzymes, originally found in fungi, plants, and other natural sources, have many industrial and biotechnological applications. They are used in the food, textile, pulp, and paper industries, as well as for bioremediation purposes. Although natural hosts can provide relatively high levels of active laccases after production optimization, heterologous expression can bring, moreover, engineered enzymes with desired properties, such as different substrate specificity or improved stability. Hence, diverse hosts suitable for laccase production are reviewed here, while the greatest emphasis is placed on yeasts which are commonly used for industrial production of various proteins. Different approaches to optimize the laccase expression and activity are also discussed in detail here.

Functional expression, production, and biochemical characterization of a laccase using yeast surface display technology

A Trametes versicolor laccase was functionally expressed on the membrane surface of Saccharomyces cerevisiae EBY100. Laccase expression was increased 6.57-fold by medium optimization and surpassed production by the native strain. Maximal laccase and biomass production reached 19 735 ± 1719 Ug^-1 and 6.22 ± 0.53 gL^-1 respectively, after 2 d of culture. Optimum oxidization of all substrates by laccase was observed at pH 3. Laccase showed high affinity towards substrates used with Km (mM) and Vmax (μmol min^-1) values of 0.57 ± 0.0047 and 24.55 ± 0.64, 1.52 ± 0.52 and 9.25 ± 1.78, and 2.67 ± 0.12 and 11.26 ± 0.75, were reported for ABTS, 2, 6-DMP and GUA, respectively. EDTA and NaN₃ displayed none competitive inhibition towards laccase activity. The optimum temperature for activity was 50 °C; however, the enzyme was stable over a wide range of temperatures (25-70 °C). The biologically immobilized laccase showed high reusability towards phenolic substrates and low reusability with non-phenolic substrates. High affinity for a diversity phenolic compounds and great ethanol tolerance substantiates this laccase/yeast biocatalyst potential for application in the production of bioethanol.

Complete biodegradation of chlorpyrifos by engineered Pseudomonas putida cells expressing surface-immobilized laccases

The long-term abuse use of chlorpyrifos-like pesticides in agriculture and horticulture has resulted in significant soil or water contamination and a worldwide ecosystem threat. In this study, the ability of a solvent-tolerant bacterium, Pseudomonas putida MB285, with surface-displayed bacterial laccase, to biodegrade chlorpyrifos was investigated. The results of compositional analyses of the degraded products demonstrate that the engineered MB285 was capable of completely eliminating chlorpyrifos via direct biodegradation, as determined by high-performance liquid chromatography and gas chromatography-mass spectrometry assays. Two intermediate metabolites, namely 3,5,6-trichloro-2-pyridinol (TCP) and diethyl phosphate, were temporarily detectable, verifying the joint and stepwise degradation of chlorpyrifos by surface laccases and certain cellular enzymes, whereas the purified free laccase incompletely degraded chlorpyrifos into TCP. The degradation reaction can be conducted over a wide range of pH values (2-7) and temperatures (5-55 °C) without the need for Cu(2+). Bioassays using Caenorhabditis elegans as an indicator organism demonstrated that the medium was completely detoxified of chlorpyrifos by degradation. Moreover, the engineered cells exhibited a high capacity of repeated degradation and good performance in continuous degradation cycles, as well as a high capacity to degrade real effluents containing chlorpyrifos. Therefore, the developed system exhibited a high degradation capacity and performance and constitutes an improved approach to address chlorpyrifos contamination in chlorpyrifos-remediation practice.

Production of dicarboxylic acids from novel unsaturated fatty acids by laccase-catalyzed oxidative cleavage

The establishment of renewable biofuel and chemical production is desirable because of global warming and the exhaustion of petroleum reserves. Sebacic acid (decanedioic acid), the material of 6,10-nylon, is produced from ricinoleic acid, a carbon-neutral material, but the process is not eco-friendly because of its energy requirements. Laccase-catalyzing oxidative cleavage of fatty acid was applied to the production of dicarboxylic acids using hydroxy and oxo fatty acids involved in the saturation metabolism of unsaturated fatty acids in Lactobacillus plantarum as substrates. Hydroxy or oxo fatty acids with a functional group near the carbon-carbon double bond were cleaved at the carbon-carbon double bond, hydroxy group, or carbonyl group by laccase and transformed into dicarboxylic acids. After 8 h, 0.58 mM of sebacic acid was produced from 1.6 mM of 10-oxo-cis-12,cis-15-octadecadienoic acid (αKetoA) with a conversion rate of 35% (mol/mol). This laccase-catalyzed enzymatic process is a promising method to produce dicarboxylic acids from biomass-derived fatty acids.

Establishment of cell surface engineering and its development

Cell surface display of proteins/peptides has been established based on mechanisms of localizing proteins to the cell surface. In contrast to conventional intracellular and extracellular (secretion) expression systems, this method, generally called an arming technology, is particularly effective when using yeasts as a host, because the control of protein folding that is often required for the preparation of proteins can be natural. This technology can be employed for basic and applied research purposes. In this review, I describe various strategies for the construction of engineered yeasts and provide an outline of the diverse applications of this technology to industrial processes such as the production of biofuels and chemicals, as well as bioremediation and health-related processes. Furthermore, this technology is suitable for novel protein engineering and directed evolution through high-throughput screening, because proteins/peptides displayed on the cell surface can be directly analyzed using intact cells without concentration and purification. Functional proteins/peptides with improved or novel functions can be created using this beneficial, powerful, and promising technique.

Reconstruction of thermotolerant yeast by one-point mutation identified through whole-genome analyses of adaptively-evolved strains

Saccharomyces cerevisiae is used as a host strain in bioproduction, because of its rapid growth, ease of genetic manipulation, and high reducing capacity. However, the heat produced during the fermentation processes inhibits the biological activities and growth of the yeast cells. We performed whole-genome sequencing of 19 intermediate strains previously obtained during adaptation experiments under heat stress; 49 mutations were found in the adaptation steps. Phylogenetic tree revealed at least five events in which these strains had acquired mutations in the CDC25 gene. Reconstructed CDC25 point mutants based on a parental strain had acquired thermotolerance without any growth defects. These mutations led to the downregulation of the cAMP-dependent protein kinase (PKA) signaling pathway, which controls a variety of processes such as cell-cycle progression and stress tolerance. The one-point mutations in CDC25 were involved in the global transcriptional regulation through the cAMP/PKA pathway. Additionally, the mutations enabled efficient ethanol fermentation at 39 °C, suggesting that the one-point mutations in CDC25 may contribute to bioproduction.

Exoproteome analysis of Clostridium cellulovorans in natural soft-biomass degradation

Clostridium cellulovorans is an anaerobic, cellulolytic bacterium, capable of effectively degrading various types of soft biomass. Its excellent capacity for degradation results from optimization of the composition of the protein complex (cellulosome) and production of non-cellulosomal proteins according to the type of substrates. In this study, we performed a quantitative proteome analysis to determine changes in the extracellular proteins produced by C. cellulovorans for degradation of several types of natural soft biomass. C. cellulovorans was cultured in media containing bagasse, corn germ, rice straw (natural soft biomass), or cellobiose (control). Using an isobaric tag method and a liquid chromatograph equipped with a long monolithic silica capillary column/mass spectrometer, we identified 372 proteins in the culture supernatant. Of these, we focused on 77 saccharification-related proteins of both cellulosomal and non-cellulosomal origins. Statistical analysis showed that 18 of the proteins were specifically produced during degradation of types of natural soft biomass. Interestingly, the protein Clocel_3197 was found and commonly involved in the degradation of every natural soft biomass studied. This protein may perform functions, in addition to its known metabolic functions, that contribute to effective degradation of natural soft biomass.

Modifying Yeast Tolerance to Inhibitory Conditions of Ethanol Production Processes

Saccharomyces cerevisiae strains having a broad range of substrate utilization, rapid substrate consumption, and conversion to ethanol, as well as good tolerance to inhibitory conditions are ideal for cost-competitive ethanol production from lignocellulose. A major drawback to directly design S. cerevisiae tolerance to inhibitory conditions of lignocellulosic ethanol production processes is the lack of knowledge about basic aspects of its cellular signaling network in response to stress. Here, we highlight the inhibitory conditions found in ethanol production processes, the targeted cellular functions, the key contributions of integrated -omics analysis to reveal cellular stress responses according to these inhibitors, and current status on design-based engineering of tolerant and efficient S. cerevisiae strains for ethanol production from lignocellulose.

Cell surface engineering of industrial microorganisms for biorefining applications

In order to decrease carbon emissions and negative environmental impacts of various pollutants, biofuel/biochemical production should be promoted for replacing fossil-based industrial processes. Utilization of abundant lignocellulosic biomass as a feedstock has recently become an attractive option. In this review, we focus on recent efforts of cell surface display using industrial microorganisms such as Escherichia coli and yeast. Cell surface display is used primarily for endowing cellulolytic activity on the host cells, and enables direct fermentation to generate useful fuels and chemicals from lignocellulosic biomass. Cell surface display systems are systematically summarized, and the drawbacks/perspectives as well as successful application of surface display for industrial biotechnology are discussed.

Cell-surface display of enzymes by the yeast Saccharomyces cerevisiae for synthetic biology

In yeast cell-surface displays, functional proteins, such as cellulases, are genetically fused to an anchor protein and expressed on the cell surface. Saccharomyces cerevisiae, which is often utilized as a cell factory for the production of fuels, chemicals, and proteins, is the most commonly used yeast for cell-surface display. To construct yeast cells with a desired function, such as the ability to utilize cellulose as a substrate for bioethanol production, cell-surface display techniques for the efficient expression of enzymes on the cell membrane need to be combined with metabolic engineering approaches for manipulating target pathways within cells. In this Minireview, we summarize the recent progress of biorefinery fields in the development and application of yeast cell-surface displays from a synthetic biology perspective and discuss approaches for further enhancing cell-surface display efficiency.

Development of new tolerant strains to hydrophilic and hydrophobic organic solvents by the yeast surface display methodology

Yeast surface display is a research methodology based on anchoring functional proteins and peptides onto the surface of the cells of this eukaryotic organism. Its development has resulted in the construction of a good number of new whole-cell biocatalysts with diverse applications in biotechnology, pharmacy, and medicine. In this work, we describe the design of new yeast strains in which several proteins and peptides have been introduced at the N-terminal position of protein agglutinin Aga2p. In all cases, proteins were correctly expressed and displayed on the cell surface according to the western blot, fluorescence microscopy, and fluorescence-activated cell sorting (FACS) analyses. The introduction of a glycosylable, Ser/Thr-rich protein (S1) resulted in improved resistance to ethanol, nonane, and dimethyl sulfoxide (DMSO) stress. The protein with a very high hydrophobic content (S2d) proved to confer tolerance to acetonitrile, ethanol, nonane, salt, and sodium dodecyl sulfate (SDS). The introduction of five leucine residues at the N-terminal position of S1 and S2 resulted in similar or increased resistance to the above-mentioned stress conditions. The adverse effects described in a previous work, when these residues were introduced into the N-terminus of Aga2p, with no other protein acting as a spacer, were not observed. Indeed, these strains grew better in the presence of hydrophilic solvents such as acetonitrile and ethanol. The new strains reported in this work have biotechnological potentiality given their behavior under adverse conditions of interest for biocatalytic and industrial processes.

Coriolopsis rigida, a potential model of white-rot fungi that produce extracellular laccases

In the last two decades, a significant amount of work aimed at studying the ability of the white-rot fungus Coriolopsis rigida strain LPSC no. 232 to degrade lignin, sterols, as well as several hazardous pollutants like dyes and aliphatic and aromatic fractions of crude oil, including polycyclic aromatic hydrocarbons, has been performed. Additionally, C. rigida in association with arbuscular mycorrhizal fungi appears to enhance plant growth, albeit the physiological and molecular bases of this effect remain to be elucidated. C. rigida's ability to degrade lignin and lignin-related compounds and the capacity to transform the aromatic fraction of crude oil in the soil might be partially ascribed to its ligninolytic enzyme system. Two extracellular laccases are the only enzymatic components of its lignin-degrading system. We reviewed the most relevant findings regarding the activity and role of C. rigida LPSC no. 232 and its laccases and discussed the work that remains to be done in order to assess, more precisely, the potential use of this fungus and its extracellular enzymes as a model in several applied processes.

Arming Technology in Yeast-Novel Strategy for Whole-cell Biocatalyst and Protein Engineering

Cell surface display of proteins/peptides, in contrast to the conventional intracellular expression, has many attractive features. This arming technology is especially effective when yeasts are used as a host, because eukaryotic modifications that are often required for functional use can be added to the surface-displayed proteins/peptides. A part of various cell wall or plasma membrane proteins can be genetically fused to the proteins/peptides of interest to be displayed. This technology, leading to the generation of so-called "arming technology", can be employed for basic and applied research purposes. In this article, we describe various strategies for the construction of arming yeasts, and outline the diverse applications of this technology to industrial processes such as biofuel and chemical productions, pollutant removal, and health-related processes, including oral vaccines. In addition, arming technology is suitable for protein engineering and directed evolution through high-throughput screening that is made possible by the feature that proteins/peptides displayed on cell surface can be directly analyzed using intact cells without concentration and purification. Actually, novel proteins/peptides with improved or developed functions have been created, and development of diagnostic/therapeutic antibodies are likely to benefit from this powerful approach.

Yeast arming by the Aga2p system: effect of growth conditions in galactose on the efficiency of the display and influence of expressing leucine-containing peptides

The amino or carboxy-terminal regions of certain cell wall proteins are capable of anchoring foreign proteins or peptides on the cell wall of the yeast Saccharomyces cerevisiae. This possibility has resulted in the development of a methodology known as yeast display which has powerful applications in biotechnology, pharmacy, and medicine. This work describes the results of experiments in which the agglutinin Aga2p protein is used as an anchor and several leucine-based peptides have been introduced into its N-terminal or C-terminal position. We found that the sequence of these peptides can affect plasmid stability, growth kinetics, and levels of the fusion protein displayed, and we analyzed how the incubation conditions influence these parameters. Besides, we show that the introduction of these small peptides can modify the properties of cell cover; in particular, fusing five or ten leucine residues to the Aga2p protein results in greater hydrophobicity of the cell wall and also in increased resistance to the presence of the organic solvents acetonitrile and ethanol and to high salt concentrations. The introduction of the RLRLL sequence also results in higher resistance to the exposure of yeast cells to NaCl stress.

Construction of a novel selection system for endoglucanases exhibiting carbohydrate-binding modules optimized for biomass using yeast cell-surface engineering

To permit direct cellulose degradation and ethanol fermentation, Saccharomyces cerevisiae BY4741 (Δsed1) codisplaying 3 cellulases (Trichoderma reesei endoglucanase II [EG], T. reesei cellobiohydrolase II [CBH], and Aspergillus aculeatus β-glucosidase I [BG]) was constructed by yeast cell-surface engineering. The EG used in this study consists of a family 1 carbohydrate-binding module (CBM) and a catalytic module. A comparison with family 1 CBMs revealed conserved amino acid residues and flexible amino acid residues. The flexible amino acid residues were at positions 18, 23, 26, and 27, through which the degrading activity for various cellulose structures in each biomass may have been optimized. To select the optimal combination of CBMs of EGs, a yeast mixture with comprehensively mutated CBM was constructed. The mixture consisted of yeasts codisplaying EG with mutated CBMs, in which 4 flexible residues were comprehensively mutated, CBH, and BG. The yeast mixture was inoculated in selection medium with newspaper as the sole carbon source. The surviving yeast consisted of RTSH yeast (the mutant sequence of CBM: N18R, S23T, S26S, and T27H) and wild-type yeast (CBM was the original) in a ratio of 1:46. The mixture (1 RTSH yeast and 46 wild-type yeasts) had a fermentation activity that was 1.5-fold higher than that of wild-type yeast alone in the early phase of saccharification and fermentation, which indicates that the yeast mixture with comprehensively mutated CBM could be used to select the optimal combination of CBMs suitable for the cellulose of each biomass.