Engineering a thermostable highly active glucose 6-phosphate dehydrogenase and its application to hydrogen production in vitro

Enzymatic characterization of a thermostable 6-phosphogluconate dehydrogenase from Hydrogenobacter thermophilus and its application for NADH regeneration

6-Phosphogluconate dehydrogenases (6PGDHs) are widely existing as reduced cofactor (NADH/NADPH) regeneration biocatalysts. Herein, a thermostable 6PGDH from Hydrogenobacter thermophilus (Ht6PGDH) was overexpressed in Escherichia coli and enzymologically characterized. Ht6PGDH exhibited exceptional stability and catalytic activity under high-temperature conditions, with an optimum temperature of 85 °C and the ability to maintain high activity for prolonged periods at 70 °C, which could be purified through a one-step heat treatment. Moreover, Ht6PGDH exhibited a preference for NAD+ with a K m value of 0.4 mM and a k cat value of 28.6 s⁻1, demonstrating a significant preference over NADP+. These properties render Ht6PGDH a potentially valuable enzyme for high-temperature bioconversion and in vitro synthetic biosystems. Additional research showed that Ht6PGDH excelled in the regeneration of NADH, achieving efficient lactate production when integrated into an in vitro synthetic biosystem containing lactate dehydrogenase (LDH). Furthermore, the cascade reaction of Ht6PGDH with glucose-6-phosphate dehydrogenase (G6PDH) was explored for NADH regeneration using starch as the substrate, further validating its potential application in complex biosynthetic systems.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04165-6.

Electrodriven ATP Synthesis via a Reconstructed Thylakoid Membrane

Nature produces ATP, the energy currency, by converting solar energy (photophosphorylation) and chemical energy (substrate-level phosphorylation and oxidative phosphorylation). Green electricity, as a significant and sustainable energy carrier, plays a crucial role in achieving a carbon-neutral society. In this work, we established and verified a novel electrodriven phosphorylation method. Spinach thylakoid membranes (TMs), enriched with ATPases, were isolated and constructed into planar TMs (pTMs) on a proton exchange membrane (PEM), effectively imparting the traditional PEM with the biological function of ATP regeneration. Following the optimization of TMs concentration and incubation time, the biological PEM was integrated into a two-compartment electrochemical cell, where ATP was successfully synthesized by ATPase of pTMs, triggered by the proton gradient potential generated during electrochemical water splitting. When a constant voltage of 3 V was applied to the electrochemical cells, ATP was synthesized at a rate of 3.16 μM min-1μgChl -1, approximately twice the rate of ΔpH-driven ATP synthesis. This design offers substantial potential for green energy applications in in vitro biotransformation (ivBT) systems.

High-Throughput Screening Techniques for the Selection of Thermostable Enzymes

The acquisition of a thermostable enzyme is an indispensable prerequisite for its successful implementation in industrial applications and the development of novel functionalities. Various protein engineering approaches, including rational design, semirational design, and directed evolution, have been employed to enhance thermostability. However, all of these approaches require sensitive and reliable high-throughput screening (HTS) technologies to efficiently and rapidly identify variants with improved properties. While numerous reviews focus on modification strategies for enhancing enzyme thermostability, there is a dearth of literature reviewing HTS methods specifically aimed at this objective. Herein, we present a comprehensive overview of various HTS methods utilized for modifying enzyme thermostability across different screening platforms. Additionally, we highlight significant recent examples that demonstrate the successful application of these methods. Furthermore, we address the technical challenges associated with HTS technologies used for screening thermostable enzyme variants and discuss valuable perspectives to promote further advancements in this field. This review serves as an authoritative reference source offering theoretical support for selecting appropriate screening strategies tailored to specific enzymes with the aim of improving their thermostability.

Biomanufacturing by In Vitro Biotransformation (ivBT) Using Purified Cascade Multi-enzymes

In vitro biotransformation (ivBT) refers to the use of an artificial biological reaction system that employs purified enzymes for the one-pot conversion of low-cost materials into biocommodities such as ethanol, organic acids, and amino acids. Unshackled from cell growth and metabolism, ivBT exhibits distinct advantages compared with metabolic engineering, including but not limited to high engineering flexibility, ease of operation, fast reaction rate, high product yields, and good scalability. These characteristics position ivBT as a promising next-generation biomanufacturing platform. Nevertheless, challenges persist in the enhancement of bulk enzyme preparation methods, the acquisition of enzymes with superior catalytic properties, and the development of sophisticated approaches for pathway design and system optimization. In alignment with the workflow of ivBT development, this chapter presents a systematic introduction to pathway design, enzyme mining and engineering, system construction, and system optimization. The chapter also proffers perspectives on ivBT development.

Pomegranate Extract Augments Energy Expenditure Counteracting the Metabolic Stress Associated with High-Fat-Diet-Induced Obesity

Obesity is associated to a low grade of chronic inflammation leading to metabolic stress, insulin resistance, metabolic syndrome, dislipidemia, cardiovascular disease, and even cancer. A Mediterranean diet has been shown to reduce systemic inflammatory factors, insulin resistance, and metabolic syndrome. In this scenario, precision nutrition may provide complementary approaches to target the metabolic alterations associated to “unhealthy obesity”. In a previous work, we described a pomegranate extract (PomE) rich in punicalagines to augment markers of browning and thermogenesis in human differentiated adipocytes and to augment the oxidative respiratory capacity in human differentiated myocytes. Herein, we have conducted a preclinical study of high-fat-diet (HFD)-induced obesity where PomE augments the systemic energy expenditure (EE) contributing to a reduction in the low grade of chronic inflammation and insulin resistance associated to obesity. At the molecular level, PomE promotes browning and thermogenesis in adipose tissue, reducing inflammatory markers and augmenting the reductive potential to control the oxidative stress associated to the HFD. PomE merits further investigation as a complementary approach to alleviate obesity, reducing the low grade of chronic inflammation and metabolic stress.

Stoichiometric Conversion of Maltose for Biomanufacturing by In Vitro Synthetic Enzymatic Biosystems

Maltose is a natural α-(1,4)-linked disaccharide with wide applications in food industries and microbial fermentation. However, maltose has scarcely been used for in vitro biosynthesis, possibly because its phosphorylation by maltose phosphorylase (MP) yields β-glucose 1-phosphate (β-G1P) that cannot be utilized by α-phosphoglucomutase (α-PGM) commonly found in in vitro synthetic enzymatic biosystems previously constructed by our group. Herein, we designed an in vitro synthetic enzymatic reaction module comprised of MP, β-phosphoglucomutase (β-PGM), and polyphosphate glucokinase (PPGK) for the stoichiometric conversion of each maltose molecule to two glucose 6-phosphate (G6P) molecules. Based on this synthetic module, we further constructed two in vitro synthetic biosystems to produce bioelectricity and fructose 1,6-diphosphate (FDP), respectively. The 14-enzyme biobattery achieved a Faraday efficiency of 96.4% and a maximal power density of 0.6 mW/cm2, whereas the 5-enzyme in vitro FDP-producing biosystem yielded 187.0 mM FDP from 50 g/L (139 mM) maltose by adopting a fed-batch substrate feeding strategy. Our study not only suggests new application scenarios for maltose but also provides novel strategies for the high-efficient production of bioelectricity and value-added biochemicals.

Efficient Asymmetric Synthesis of (S)-N-Boc-3-Hydroxypiperidine by Coexpressing Ketoreductase and Glucose Dehydrogenase

(S)-N-Boc-3-hydroxypiperidine is an important intermediate of the anticancer drug ibrutinib and is mainly synthesized by the asymmetric reduction catalyzed by ketoreductase coupled with glucose dehydrogenase at present. In this study, the coexpression recombinant strains E. coli/pET28-K-rbs-G with single promoter and E. coli/pETDuet-K-G with double promoters were first constructed for the coexpression of ketoreductase and glucose dehydrogenase in the same cell. Then, the catalytic efficiency of E. coli/pET28-K-rbs-G for synthesizing (S)-N-Boc-3-hydroxypiperidine was found to be higher than that of E. coli/pETDuet-K-G due to the more balanced activity ratio and higher catalytic activity. On this basis, the catalytic conditions of E. coli/pET28-K-rbs-G were further optimized, and finally both the conversion of the reaction and the optical purity of the product were higher than 99%. In the end, the cell-free extract was proved to be a better catalyst than the whole cell with the improved catalytic efficiency of different recombinant strains. This study developed a better coexpression strategy for ketoreductase and glucose dehydrogenase by investigating the effect of activity ratios and forms of the biocatalysts on the catalytic efficiency deeply, which provided a research basis for the efficient synthesis of chiral compounds.

Unusual substrate specificity in GH family 12: structure-function analysis of glucanases Bgh12A and Xgh12B from Aspergillus cervinus, and Egh12 from Thielavia terrestris

In this study, we compared the properties and structures of three fungal GH12 enzymes: the strict endoglucanase Bgh12A and the xyloglucanase Xgh12B from Aspergillus cervinus, and the endoglucanase Egh12 from Thielavia terrestris combining activity on linear β-glucan and branched xyloglucan. Egh12 from T. terrestris was produced in Pichia pastoris, purified, and characterized as a thermostable enzyme with maximal activity at 70 ºC and a half-life time of 138 min at 65 °C. We for the first time demonstrated that the GH12 endoglucanases Egh12 and Bgh12A, but not the strict xyloglucanase Xgh12B, hydrolyzed (1,3)-β-linkages in (1,3;1,4)-β-D-glucooligosaccharides and had transglycosylase activity on (1,3)-β-D-glucooligosaccharides. Phylogenetic analysis indicated that Egh12 from T. terrestris and Bgh12A from A. cervinus are more related than Bgh12A and Xgh12B isolated from one strain. The X-ray structure of Bgh12A was determined with 2.17 Å resolution and compared with 3D-homology models of Egh12 and Xgh12B. The enzymes have a β-jelly roll structure with a catalytic cleft running across the protein. Comparative analysis and a docking study demonstrated the importance of endoglucanase-specific loop 1 partly covering the catalytic cleft for correct placement of the linear substrates. Variability in substrate specificity between the GH12 endoglucanases is determined by non-conservative residues in structural loops framing the catalytic cleft. A residue responsible for the thermostability of Egh12 was predicted. The key structural elements and residues described in this study may serve as potential targets for modification aimed at the improvement of enzymatic properties. KEY POINTS: • Thermostable endoglucanase Egh12 from T. terrestris was produced in P. pastoris, purified, and characterized • The X-ray structure of GH12 endoglucanase Bgh12A from A. cervinus was resolved • GH12 endoglucanases, but not GH12 xyloglucanases, hydrolyze (1,3)-β-linkages in (1,3;1,4)-β-D-glucooligosaccharides.

Photoswitchable Enzymatic Biofuel Cell Based on Fusion Protein with Natural Photoreceptor Vivid

Enzymatic biofuel cells (EBFCs) have increasingly been the subject of research, but the control of the EBFC output remains difficult. In this study, we fuse glucose 6-phosphate dehydrogenase (G6PDH) and diaphorase (DI) with the natural photoreceptor Vivid named "Mag". The output current and power density of EBFCs with the fusion protein exhibit a sensitive and efficient response to blue light. Following optimizations, the power density increases nearly 4-fold from 1.32 to 6.26 μW cm^-2, whereas the current rises from 5.9 to 10.8 μA after 20 min of illumination, dropping back within 30 min under dark conditions.

Yeast Surface Display for In Vitro Biosynthetic Pathway Reconstruction

The enzymes immobilized through yeast surface display (YSD) can be used in in vitro metabolic pathway reconstruction as alternatives to the enzymes isolated or purified through conventional biochemistry methods. They can be easily prepared by growing and collecting yeast cells harboring display constructs. This may provide an economical method for enriching certain enzymes for biochemistry characterization and application. Herein, we took the advantage of one-pot cascade reactions catalyzed by YSD-immobilized enzymes in the mevalonate pathway to produce geraniol in vitro. YSD-immobilized enzymes of 10 cascade reactions for geraniol production, together with optimization of catalytic components, cofactor regeneration, and byproduct removal, achieved a final yield of 7.55 mg L^-1 after seven cycles. This study demonstrated that it is feasible to reconstitute a complex multi-enzymatic system for the chemical biosynthesis in vitro by exploiting YSD-immobilized cascade enzymes.

Efficient Biosynthesis of Raspberry Ketone by Engineered Escherichia coli Coexpressing Zingerone Synthase and Glucose Dehydrogenase

Raspberry ketone (RK), the main aroma compound of raspberry fruit, has applications in cosmetics, food industry, and pharmaceutics. In this study, we biosynthesized RK via the catalytic reduction of 4-hydroxybenzylidenacetone using a whole-cell biocatalyst. Reductase RiRZS1 from Rubus idaeus and glucose dehydrogenase SyGDH from Thermoplasma acidophilum were expressed in Escherichia coli to regenerate NADPH for the whole-cell catalytic reaction. Following the optimization of balancing the coexpression of two enzymes in pRSFDuet-1, we obtained 9.89 g/L RK with a conversion rate of 98% and a space-time yield of 4.94 g/(L·h). The optimum conditions are 40 °C, pH 5.5, and a molar ratio of substrate to auxiliary substrate of 1:2.5. Our study findings provide a promising method of biosynthesizing RK.

Strategic aromatic residues in the catalytic cleft of the xyloglucanase MtXgh74 modifying thermostability, mode of enzyme action, and viscosity reduction ability

The thermostable endo-processive xyloglucanase MtXgh74 from Myceliophthora thermophila was used to study the influence of aromatic amino acids in the catalytic cleft on the mode of action and the ability of enzyme to reduce xyloglucan viscosity. The enzyme derivative Mut I with mutations W64A/W67A in the "negative" subsites of the catalytic cleft resulted in a 5.5-fold increase of the K_m value. Mut I produced oligosaccharides of various lengths in addition to xyloglucan building blocks. The W320A/W321A substitutions in the "positive" subsites of the mutated enzyme Mut II catalytic cleft increased the K_m value 54-fold and resulted in an endo-dissociative mode of action. The ability of Mut II to reduce the viscosity of xyloglucan at 50 °C was much better than that of other MtXgh74 variants. Besides, Mut II efficiently reduced viscosity of a natural substrate, the pulp of xyloglucan-containing tamarind seed flour. The K_m, V_max, and k_cat values and viscosity reduction ability of the enzyme derivative Mut III (W320A/W321A/G446Y) returned to levels close to that of MtXgh74. The pattern of xyloglucan hydrolysis by Mut III was typical for endo-processive xyloglucanases. The thermostability of Mut I and Mut II at 60 °C decreased significantly compared to the wild type, whereas the thermostability of Mut III at 60 °C restored almost to the MtXgh74-wt value. All mutants lost the ability to cleave the backbone of xyloglucan building blocks which was a characteristic of MtXgh74. Instead they acquired a low branch removing activity. Molecular dynamics simulations revealed the role of mutated amino acids in the complex action mechanism of GH74 enzymes. KEY POINTS: • Endo-processive mode of action of the xyloglucanase MtXgh74 was altered by rational design. • The endo-dissociative mutant Mut II (W320A/W321A) efficiently reduced XyG viscosity. • The substitutions W320A/W321A/G446Y in Mut III recovered the endo-processive mode. • Mut II can be used to reduce the viscosity of biomass slurries containing tamarind seed flour.

In Vivo, High-Throughput Selection of Thermostable Cyclohexanone Monooxygenase (CHMO)

Cyclohexanone monooxygenase (CHMO) from Acinetobacter sp. NCIMB 9871 is characterized as having wide substrate versatility for the biooxidation of (cyclic) ketones into esters and lactones with high stereospecificity. Despite industrial potential, CHMO usage is restricted by poor thermostability. Limited high-throughput screening tools and challenges in rationally engineering thermostability have impeded CHMO engineering efforts. We demonstrate the application of an aerobic, high-throughput growth selection platform in Escherichia coli (strain MX203) for the discovery of thermostability enhancing mutations for CHMO. The selection employs growth for the easy readout of CHMO activity in vivo, by requiring nicotinamide adenine dinucleotide phosphate (NADPH)-consuming enzymes to restore cellular redox balance. In the presence of the native substrate cyclohexanone, variant CHMO GV (A245G-A288V) was discovered from a random mutagenesis library screened at 42 °C. This variant retained native activity, exhibited ~4.4-fold improvement in residual activity after 30 °C incubation, and demonstrated ~5-fold higher cyclohexanone conversion at 37 °C compared to the wild type. Molecular modeling indicates that CHMO GV experiences more favorable residue packing and supports additional backbone hydrogen bonding. Further rational design resulted in CHMO A245G-A288V-T415C with improved thermostability at 45 °C. Our platform for oxygenase evolution enabled the rapid engineering of protein stability critical for industrial scalability.

Engineering of β-Glucosidase Bgl15 with Simultaneously Enhanced Glucose Tolerance and Thermostability To Improve Its Performance in High-Solid Cellulose Hydrolysis

In this study, a Petri-dish-based double-layer high-throughput screening method was established to improve glucose tolerance of β-glucosidase Bgl15. Two beneficial mutations were identified, and the joint mutant 2R1 improved the half-maximal inhibitory concentration of glucose from 0.04 to 2.1 M. The crystal structure of 2R1 was subsequently determined at 2.7 Å. Structure analysis revealed that enhancement of glucose tolerance may be due to improved transglycosylation activity made possible by a hydrophobic binding site for glucose as an acceptor and more stringent control of a putative water channel. To further ameliorate the application potential of the enzyme, it was engineered to increase the half-life at 50 °C from 0.8 h (Bgl15) to 180 h (mutant 5R1). Furthermore, supplementation of 5R1 to the cellulase cocktail significantly improved glucose production from pretreated sugar cane bagasse by 38%. Consequently, this study provided an efficient approach to enhance glucose tolerance and generated a promising catalyst for cellulose saccharification.

Efficient Multi-Enzymes Immobilized on Porous Microspheres for Producing Inositol From Starch

In vitro synthetic enzymatic biosystem is considered to be the next generation of biomanufacturing platform. This biosystem contains multiple enzymes for the implementation of complicated biotransformatiom. However, the hard-to-reuse and instability of multiple enzymes limit the utilization of this biosystem in industrial process. Multi-enzyme immobilization might be a feasible alternative to address these problems. Herein, porous microspheres are used as carriers to co-immobilize multiple enzymes for producing inositol from starch. At first, all the enzymes (i.e., α-glucan phosphorylase aGP, phosphoglucose mutase PGM, inositol 1-phosphate synthase IPS, and inositol monophosphatase IMP) for converting starch to inositol were immobilized on porous microspheres individually to check the effect of immobilization, then all the enzymes are co-immobilized on porous microspheres. Compared to reaction system containing all the individual immobilized enzymes, the reaction system containing the co-immobilized enzymes exhibit ∼3.5 fold of reaction rate on producing inositol from starch. This reaction rate is comparable to that by free enzyme mixture. And the co-immobilized multi-enzyme system show higher thermal stability and recovery stability than free enzyme mixture. After 7 batches, the immobilized enzymes retain 45.6% relative yield, while the free enzyme mixture only retain 13.3% relative yield after 3 batches. Co-immobilization of multiple enzymes on porous microspheres for biomanufacturing would shed light on the application of in vitro synthetic enzymatic biosystem in industrial scale.

A High-Throughput Method for Directed Evolution of NAD(P)+-Dependent Dehydrogenases for the Reduction of Biomimetic Nicotinamide Analogues

Engineering flavin-free NAD(P)⁺-dependent dehydrogenases to reduce biomimetic nicotinamide analogues (mNAD⁺s) is of importance for eliminating the need for costly NAD(P)⁺ in coenzyme regeneration systems. Current redox dye-based screening methods for engineering the mNAD⁺ specificity of dehydrogenases are frequently encumbered by a background signal from endogenous NAD(P) and intracellular reducing compounds, making the detection of low mNAD⁺-based activities a limiting factor for directed evolution. Here, we develop a high-throughput screening method, NAD(P)-eliminated solid-phase assay (NESPA), which can reliably identify mNAD⁺-active mutants of dehydrogenases with a minimal background signal. This method involves (1) heat lysis of colonies to permeabilize the cell membrane, (2) colony transfer onto filter paper, (3) washing to remove endogenous NAD(P) and reducing compounds, (4) enzyme-coupled assay for mNADH-dependent color production, and (5) digital imaging of colonies to identify mNAD⁺-active mutants. This method was used to improve the activity of 6-phosphogluconate dehydrogenase on nicotinamide mononucleotide (NMN⁺). The best mutant obtained after six rounds of directed evolution exhibits a 50-fold enhancement in catalytic efficiency (k _cat/K _M) and a specific activity of 17.7 U/mg on NMN⁺, which is comparable to the wild-type enzyme on its natural coenzyme, NADP⁺. The engineered dehydrogenase was then used to construct an NMNH regeneration system to drive an ene-reductase catalysis. A comparable level of turnover frequency and product yield was observed using the engineered system relative to NADPH regeneration by using the wild-type dehydrogenase. NESPA provides a simple and accurate readout of mNAD⁺-based activities and the screening at high-throughput levels (approximately tens of thousands per round), thus opening up an avenue for the evolution of dehydrogenases with specific activities on mNAD⁺s similar to the levels of natural enzyme/coenzyme pairs.

Protein engineering for bioreduction of carboxylic acids

Carboxylic acids (CAs) are widespread in Nature. A prominent example is fatty acids, a major constituent of lipids. CAs are potentially economical precursors for bio-based products such as bio-aldehydes and bio-alcohols. However, carboxylate reduction is a challenging chemical transformation due to the thermodynamic stability of carboxylate. Carboxylic acid reductases (CARs), found in bacteria and fungi, offer a good solution to this challenge. These enzymes catalyse the NADPH- and ATP-dependent reduction of aliphatic and aromatic CAs. This review summarised all the protein engineering work that has been done on these versatile biocatalysts to date. The intricate catalytic mechanism and structure of CARs prompted us to first examine their domain architecture to facilitate the subsequent discussion of various protein engineering strategies. This then led to a survey of assays to detect aldehyde formation and to monitor aldenylation activity. Strategies for NADPH and ATP regeneration were also incorporated, as they are deemed vital to developing preparative-scale biocatalytic process and high-throughput screening systems. The objectives of the review are to consolidate CAR engineering research, stimulate interest, discussion or debate, and advance the field of bioreduction.

Acceleration of cellodextrin phosphorolysis for bioelectricity generation from cellulosic biomass by integrating a synthetic two-enzyme complex into an in vitro synthetic enzymatic biosystem

BACKGROUND

Cellulosic biomass, the earth's most abundant renewable resource, can be used as substrates for biomanufacturing biofuels or biochemicals via in vitro synthetic enzymatic biosystems in which the first step is the enzymatic phosphorolysis of cellodextrin to glucose 1-phosphate (G1P) by cellodextrin phosphorylase (CDP). However, almost all the CDPs prefer cellodextrin synthesis to phosphorolysis, resulting in the low reaction rate of cellodextrin phosphorolysis for biomanufacturing.

RESULTS

To increase the reaction rate of cellodextrin phosphorolysis, synthetic enzyme complexes containing CDP and phosphoglucomutase (PGM) were constructed to convert G1P to glucose 6-phosphate (G6P) rapidly, which is an important intermediate for biomanufacturing. Four self-assembled synthetic enzyme complexes were constructed with different spatial organizations based on the high-affinity and high-specific interaction between cohesins and dockerins from natural cellulosomes. Thus, the CDP-PGM enzyme complex with the highest enhancement of initial reaction rate was integrated into an in vitro synthetic enzymatic biosystem for generating bioelectricity from cellodextrin. The in vitro biosystem containing the best CDP-PGM enzyme complex exhibited a much higher current density (3.35-fold) and power density (2.14-fold) than its counterpart biosystem containing free CDP and PGM mixture.

CONCLUSIONS

Hereby, we first reported bioelectricity generation from cellulosic biomass via in vitro synthetic enzymatic biosystems. This work provided a strategy of how to link non-energetically favorable reaction (cellodextrin phosphorolysis) and energetically favorable reaction (G1P to G6P) together to circumvent unfavorable reaction equilibrium and shed light on improving the reaction efficiency of in vitro synthetic enzymatic biosystems through the construction of synthetic enzyme complexes.

Enhancing the Thermostability of Highly Active and Glucose-Tolerant β-Glucosidase Ks5A7 by Directed Evolution for Good Performance of Three Properties

A high-performance β-glucosidase for efficient cellulose hydrolysis needs to excel in thermostability, catalytic efficiency, and resistance to glucose inhibition. However, it is challenging to achieve superb properties in all three aspects in a single enzyme. In this study, a hyperactive and glucose-tolerant β-glucosidase Ks5A7 was employed as the starting point. Four rounds of random mutagenesis were then performed, giving rise to a thermostable mutant 4R1 with five amino acid substitutions. The half-life of 4R1 at 50 °C is 8640-fold that of Ks5A7 (144 h vs 1 min). Meanwhile, 4R1 had a higher specific activity (374.26 vs 243.18 units·mg^-1) than the wild type with a similar glucose tolerance. When supplemented to Celluclast 1.5L, the mutant significantly enhanced the hydrolysis of pretreated sugar cane bagasse, improving the released glucose concentration by 44%. With excellent performance in thermostability, activity, and glucose tolerance, 4R1 will serve as an exceptional catalyst for industrial applications.