Man/Cel5B, a Bifunctional Enzyme Having the Highest Mannanase Activity in the Hyperthermic Environment

A combined model based on lung CT imaging and clinical characteristics for the diagnosis of AIDS with infection of Talaromyces marneffei

OBJECTIVE

To construct a combined model based on the CT and clinical characteristics of acquired immune deficiency syndrome (AIDS) with infection of Talaromyces marneffei (TM) and evaluate the diagnostic efficacy of the combined model.

METHODS

A retrospective analysis was conducted on 225 patients with AIDS patients with pulmonary infection admitted to the Shanghai Public Health Clinical Center from February 2012 to October 2022. Based on the final microbiological test results, they were divided into a group infected with TM and a group not infected with TM. Univariate and multivariate analyses were conducted on the lung CT imaging and clinical characteristics of these 225 patients. A nomogram was used to construct a combined model, and a calibration plot was drawn to test the diagnostic efficacy of the combined model.

RESULTS

Multivariate logistic regression analysis showed that fever, rash, elevated PLT, elevated Hb, CD4+T lymphocyte count < 50/ul, and lung CT histology features including diffuse punctate and nodular shadows, mass-like consolidation, consolidation shadows, single or multiple lung abscesses or cyst shadows, and pleural effusion were independent risk factors for the diagnosis of AIDS with TM infection (P < 0.05). The construction of a joint model using nomogram and calibration plot showed that the constructed joint model had a high degree of fit.

CONCLUSION

The combined model constructed in this study has certain clinical value for evaluating whether AIDS co-infection is caused by TM.

CLINICAL TRIAL

Not applicable.

Expression and characterization of a novel microbial GH9 glucanase, IDSGLUC9-4, isolated from sheep rumen

OBJECTIVE

This study aimed to identify and characterize a novel endo-β-glucanase, IDSGLUC9-4, from the rumen metatranscriptome of Hu sheep.

METHODS

A novel endo-β-glucanase, IDSGLUC9-4, was heterologously expressed in Escherichia coli and biochemically characterized. The optimal temperature and pH of recombinant IDSGLUC9-4 were determined. Subsequently, substrate specificity of the enzyme was assessed using mixed-linked glucans including barley β-glucan and Icelandic moss lichenan. Thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), matrix assisted laser desorption ionization time of flight mass spectrometry analyses were conducted to determine the products released from polysaccharides and cello-oligosaccharides substrates.

RESULTS

The recombinant IDSGLUC9-4 exhibited temperature and pH optima of 40°C and pH 6.0, respectively. It exclusively hydrolyzed mixed-linked glucans, with significant activity observed for barley β-glucan (109.59±3.61 μmol/mg min) and Icelandic moss lichenan (35.35±1.55 μmol/mg min). TLC and HPLC analyses revealed that IDSGLUC9-4 primarily released cellobiose, cellotriose, and cellotetraose from polysaccharide substrates. Furthermore, after 48 h of reaction, IDSGLUC9-4 removed most of the glucose, indicating transglycosylation activity alongside its endo-glucanase activity.

CONCLUSION

The recombinant IDSGLUC9-4 was a relatively acid-resistant, mesophilic endo-glucanase (EC 3.2.1.4) that hydrolyzed glucan-like substrates, generating predominantly G3 and G4 oligosaccharides, and which appeared to have glycosylation activity. These findings provided insights into the substrate specificity and product profiles of rumen-derived GH9 glucanases and contributed to the expanding knowledge of cellulolytic enzymes and novel herbivore rumen enzymes in general.

Carbohydrate polymer degradation derivatives as possible natural mannanase inhibitors

The role of mannanases is diverse and they are used in many industrial applications, in animal feed, in the food industry and in healthcare. They are also applied in biomass processing, because they play an important role in the breakdown of hemicellulose. Among the mannanase inhibitors, heavy metal ions and general enzyme inhibitors are mainly mentioned. Unfortunately, almost no data are available on carbohydrate-based natural inhibitors of mannanases. According to the literature, carbohydrates do not play an important role in the inhibition of mannanases, so neither do oligosaccharides. This is in contrast to the action and inhibition of other O-glycosyl hydrolases. My hypothesis is that mannanases, like other polysaccharide-degrading enzymes, work in the same way and can be inhibited by oligosaccharides. Evidence from docking and modeling results supports and makes probable the hypothesis that oligosaccharides can inhibit the activity of mannanases, similar to the inhibition of other O-glycosyl hydrolases. Among natural carbohydrate oligomers, several potential mannanase inhibitors have been identified and characterized. In addition to expensive research, it is very important to use research based on cheaper modeling to explore the processes. The results obtained are novel and forward-looking, enabling in-depth and targeted research to be carried out.

A rumen-derived bifunctional glucanase/mannanase uncanonically releases oligosaccharides with a high degree of polymerization preferentially from branched substrates

Glycoside hydrolases (GHs) are known to depolymerize polysaccharides into oligo-/mono-saccharides, they are extensively used as additives for both animals feed and our food. Here we reported the characterization of IDSGH5-14(CD), a weakly-acidic mesophilic bifunctional mannanase/glucanase of GH5, originally isolated from sheep rumen microbes. Biochemical characterization studies revealed that IDSGH5-14(CD) exhibited preferential hydrolysis of mannan-like and glucan-like substrates. Interestingly, the enzyme exhibited significantly robust catalytic activity towards branched-substrates compared to linear polysaccharides (P < 0.05). Substrate hydrolysis pattern indicated that IDSGH5-14(CD) predominantly liberated oligosaccharides with a degree of polymerization (DP) of 3-7 as the end products, dramatically distinct from canonical endo-acting enzymes. Comparative modeling revealed that IDSGH5-14(CD) was mainly comprised of a (β/α)8-barrel-like structure with a spacious catalytic cleft on surface, facilitating the enzyme to target high-DP or branched oligosaccharides. Molecular dynamics (MD) simulations further suggested that the branched-ligand, 64-α-D-galactosyl-mannohexose, was steadily accommodated within the catalytic pocket via a two-sided clamp formed by the aromatic residues. This study first reports a bifunctional GH5 enzyme that predominantly generates high-DP oligosaccharides, preferentially from branched-substrates. This provides novel insights into the catalytic mechanism and molecular underpinnings of polysaccharide depolymerization, with potential implications for feed additive development and high-DP oligosaccharides preparation.

Thermophilic β-mannanases from bacteria: production, resources, structural features and bioengineering strategies

β-mannanases are pivotal enzymes that cleave the mannan backbone to release short chain mannooligosaccharides, which have tremendous biotechnological applications including food/feed, prebiotics and biofuel production. Due to the high temperature conditions in many industrial applications, thermophilic mannanases seem to have great potential to overcome the thermal impediments. Thus, structural analysis of thermostable β-mannanases is extremely important, as it could open up new avenues for genetic engineering, and protein engineering of these enzymes with enhanced properties and catalytic efficiencies. Under this scope, the present review provides a state-of-the-art discussion on the thermophilic β-mannanases from bacterial origin, their production, engineering and structural characterization. It covers broad insights into various molecular biology techniques such as gene mutagenesis, heterologous gene expression, and protein engineering, that are employed to improve the catalytic efficiency and thermostability of bacterial mannanases for potential industrial applications. Further, the bottlenecks associated with mannanase production and process optimization are also discussed. Finally, future research related to bioengineering of mannanases with novel protein expression systems for commercial applications are also elaborated.

Mining thermophiles for biotechnologically relevant enzymes: evaluating the potential of European and Caucasian hot springs

The development of sustainable and environmentally friendly industrial processes is becoming very crucial and demanding for the rapid implementation of innovative bio-based technologies. Natural extreme environments harbor the potential for discovering and utilizing highly specific and efficient biocatalysts that are adapted to harsh conditions. This review focuses on extremophilic microorganisms and their enzymes (extremozymes) from various hot springs, shallow marine vents, and other geothermal habitats in Europe and the Caucasus region. These hot environments have been partially investigated and analyzed for microbial diversity and enzymology. Hotspots like Iceland, Italy, and the Azores harbor unique microorganisms, including bacteria and archaea. The latest results demonstrate a great potential for the discovery of new microbial species and unique enzymes that can be explored for the development of Circular Bioeconomy.Different screening approaches have been used to discover enzymes that are active at extremes of temperature (up 120 °C), pH (0.1 to 11), high salt concentration (up to 30%) as well as activity in the presence of solvents (up to 99%). The majority of published enzymes were revealed from bacterial or archaeal isolates by traditional activity-based screening techniques. However, the latest developments in molecular biology, bioinformatics, and genomics have revolutionized life science technologies. Post-genomic era has contributed to the discovery of millions of sequences coding for a huge number of biocatalysts. Both strategies, activity- and sequence-based screening approaches, are complementary and contribute to the discovery of unique enzymes that have not been extensively utilized so far.

Microbial β-glucanases: production, properties, and engineering

Lignocellulosic biomass, which mainly consists of cellulose and hemicellulose, is the most abundant renewable biopolymer on earth. β-Glucanases are glycoside hydrolases (GHs) that hydrolyze β-glucan, one of the dominant components of the plant cell wall, into cello-oligosaccharides and glucose. Among them, endo-β-1,4-glucanase (EC 3.2.1.4), exo-glucanase/cellobiohydrolase (EC 3.2.1.91), and β-glucosidase (EC 3.2.1.21) play critical roles in the digestion of glucan-like substrates. β-Glucanases have attracted considerable interest within the scientific community due to their applications in the feed, food, and textile industries. In the past decade, there has been considerable progress in the discovery, production, and characterization of novel β-glucanases. Advances in the development of next-generation sequencing techniques, including metagenomics and metatranscriptomics, have unveiled novel β-glucanases isolated from the gastrointestinal microbiota. The study of β-glucanases is beneficial for research and development of commercial products. In this study, we review the classification, properties, and engineering of β-glucanases.

Glycoside hydrolase subfamily GH5_57 features a highly redesigned catalytic interface to process complex hetero-β-mannans

Glycoside hydrolase family 5 (GH5) harbors diverse substrate specificities and modes of action, exhibiting notable molecular adaptations to cope with the stereochemical complexity imposed by glycosides and carbohydrates such as cellulose, xyloglucan, mixed-linkage β-glucan, laminarin, (hetero)xylan, (hetero)mannan, galactan, chitosan, N-glycan, rutin and hesperidin. GH5 has been divided into subfamilies, many with higher functional specificity, several of which have not been characterized to date and some that have yet to be discovered with the exploration of sequence/taxonomic diversity. In this work, the current GH5 subfamily inventory is expanded with the discovery of the GH5_57 subfamily by describing an endo-β-mannanase (CapGH5_57) from an uncultured Bacteroidales bacterium recovered from the capybara gut microbiota. Biochemical characterization showed that CapGH5_57 is active on glucomannan, releasing oligosaccharides with a degree of polymerization from 2 to 6, indicating it to be an endo-β-mannanase. The crystal structure, which was solved using single-wavelength anomalous diffraction, revealed a massively redesigned catalytic interface compared with GH5 mannanases. The typical aromatic platforms and the characteristic α-helix-containing β6–α6 loop in the positive-subsite region of GH5_7 mannanases are absent in CapGH5_57, generating a large and open catalytic interface that might favor the binding of branched substrates. Supporting this, CapGH5_57 contains a tryptophan residue adjacent and perpendicular to the cleavage site, indicative of an anchoring site for a substrate with a substitution at the −1 glycosyl moiety. Taken together, these results suggest that despite presenting endo activity on glucomannan, CapGH5_57 may have a new type of substituted heteromannan as its natural substrate. This work demonstrates the still great potential for discoveries regarding the mechanistic and functional diversity of this large and polyspecific GH family by unveiling a novel catalytic interface sculpted to recognize complex heteromannans, which led to the establishment of the GH5_57 subfamily.

Modifying Thermostability and Reusability of Hyperthermophilic Mannanase by Immobilization on Glutaraldehyde Cross-Linked Chitosan Beads

In the current study, the purified β-mannanase (Man/Cel5B) from Thermotoga maritima was immobilized on glutaraldehyde cross-linked chitosan beads. The immobilization of Man/Cel5B on chitosan beads was confirmed by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. After immobilization, the protein loading efficiency and immobilization yield were found to be 73.3% and 71.8%, respectively. The optimum pH for both free and immobilized enzymes was found to be pH 5.5. However, the optimum temperature of immobilized Man/Cel5B increased by 10 °C, from 85 °C (free Man/Cel5B) to 95 °C (Immobilized). The half-life of free and immobilized enzymes was found to be 7 h and 9 h, respectively, at 85 °C owing to the higher thermostability of immobilized Man/Cel5B. The increase in thermostability was also demonstrated by an increase in the energy of deactivation (209 kJmol⁻¹) for immobilized enzyme compared to its native form (92 kJmol⁻¹), at 85 °C. Furthermore, the immobilized Man/Cel5B displayed good operational stability as it retained 54% of its original activity after 15 repeated catalytic reactions concerning its free form.

Genus Thermotoga: A valuable home of multifunctional glycoside hydrolases (GHs) for industrial sustainability

Nature is a dexterous and prolific chemist for cataloging a number of hostile niches that are the ideal residence of various thermophiles. Apart from having other species, these subsurface environments are considered a throne of bacterial genus Thermotoga. The genome sequence of Thermotogales encodes complex and incongruent clusters of glycoside hydrolases (GHs), which are superior to their mesophilic counterparts and play a prominent role in various applications due to their extreme intrinsic stability. They have a tremendous capacity to use a wide variety of simple and multifaceted carbohydrates through GHs, formulate fermentative hydrogen and bioethanol at extraordinary yield, and catalyze high-temperature reactions for various biotechnological applications. Nevertheless, no stringent rules exist for the thermo-stabilization of biocatalysts present in the genus Thermotoga. These enzymes endure immense attraction in fundamental aspects of how these polypeptides attain and stabilize their distinctive three-dimensional (3D) structures to accomplish their physiological roles. Moreover, numerous genome sequences from Thermotoga species have revealed a significant fraction of genes most closely related to those of archaeal species, thus firming a staunch belief of lateral gene transfer mechanism. However, the question of its magnitude is still in its infancy. In addition to GHs, this genus is a paragon of encapsulins which carry pharmacological and industrial significance in the field of life sciences. This review highlights an intricate balance between the genomic organizations, factors inducing the thermostability, and pharmacological and industrial applications of GHs isolated from genus Thermotoga.

Heterologous expression and characterization of glycoside hydrolase with its potential applications in hyperthermic environment

With the progressive focus on renewable energy via biofuels production from lignocellulosic biomass, cellulases are the key enzymes that play a fundamental role in this regard. This study aims to unravel the characteristics of Thermotoga maritima MSB8 (Tma) (a hyperthermophile from hot springs) thermostable glycoside hydrolase enzyme. Here, a glycoside hydrolase gene of Thermotoga maritima (Tma) was heterologously expressed and characterized. The gene was placed in the pQE-30 expression vector under the T5 promotor, and the construct pQE-30-Gh was then successfully integrated into Escherichia coli BL21 (DH5α) genome by transformation. Sequence of the glycoside hydrolase contained an open reading frame of 2.124 kbp, encoded a polypeptide of 721 amino acid residues. The molecular weight of the recombinant protein estimated was 79 kDa. The glycoside hydrolase was purified by Ni⁺²-NTA affinity chromatography and its enzymatic activity was investigated. The recombinant enzyme is highly stable within an extreme pH range (2.0–7.0) and highly thermostable at 80 °C for 72 h indicating its viability in hyperthermic environment and acidic nature. Moreover, the Ca²⁺ and Mn²⁺ introduction stimulated the residual activity of recombinant enzyme. Conclusively, the thermostable glycoside hydrolase possesses potential to be exploited for industrial applications at hyperthermic environment.

Valorization Potential of a Novel Bacterial Strain, Bacillus altitudinis RSP75, towards Lignocellulose Bioconversion: An Assessment of Symbiotic Bacteria from the Stored Grain Pest, Tribolium castaneum

Bioconversion of lignocellulose into renewable energy and commodity products faces a major obstacle of inefficient saccharification due to its recalcitrant structure. In nature, lignocellulose is efficiently degraded by some insects, including termites and beetles, potentially due to the contribution from symbiotic gut bacteria. To this end, the presented investigation reports the isolation and characterization of cellulolytic bacteria from the gut system of red flour beetle, Tribolium castaneum. Out of the 15 isolated bacteria, strain RSP75 showed the highest cellulolytic activities by forming a clearance zone of 28 mm in diameter with a hydrolytic capacity of ~4.7. The MALDI-TOF biotyping and 16S rRNA gene sequencing revealed that the strain RSP75 belongs to Bacillus altitudinis. Among the tested enzymes, B. altitudinis RSP75 showed maximum activity of 63.2 IU/mL extract for xylanase followed by β-glucosidase (47.1 ± 3 IU/mL extract) which were manifold higher than previously reported activities. The highest substrate degradation was achieved with wheat husk and corn cob powder which accounted for 69.2% and 54.5%, respectively. The scanning electron microscopy showed adhesion of the bacterial cells with the substrate which was further substantiated by FTIR analysis that depicted the absence of the characteristic cellulose bands at wave numbers 1247, 1375, and 1735 cm^-1 due to hydrolysis by the bacterium. Furthermore, B. altitudinis RSP75 showed co-culturing competence with Saccharomyces cerevisiae for bioethanol production from lignocellulose as revealed by GC-MS analysis. The overall observations signify the gut of T. castaneum as a unique and impressive reservoir to prospect for lignocellulose-degrading bacteria that can have many biotechnological applications, including biofuels and biorefinery.

Epiphytic bet-mannanase producing bacterial strains

Dry remains of the herbal species of the plantain (Plantago major), the wormwood (Artemisia vulgaris) and the reed grass (Calamagrostis acutiflora) were used as a natural source for isolation of β- mannanase producing strains. They were isolated by using the carob gum as a single source of carbon and energy. Each chosen plant species was found to be colonized with a single dominant epiphytic group of microorganism, although the plants had been collected in the same location. Bacillus circulans was only found in P. major, Bacillus subtilis on A. vulgaris, whereas Pantoea sp. was found in C. acutiflora. Identification of the taxonomy affiliation of the isolated β-mannanase producers allowed using the formerly proposed primers for PCR cloning of β-mannanase genes previously occurred in the respective bacterial species. This approach let us cloning 330 bp fragment of β-mannanase genes from B. circulans and B. subtilis and 1000 bp fragment of β-mannanase gene from Pantoea sp. Testing the enzymatic activity of the isolated strains by staining the carob gum hydrolysis zones on the plates with Congo Red was carried out. As a result, the maximum activity was found in Pantoea sp.