Interactions between soil compositions and the wheat root microbiome under drought stress: From an in silico to in planta perspective

As wheat (Triticum aestivum) is an important staple food across the world, preservation of stable yields and increased productivity are major objectives in breeding programs. Drought is a global concern because its adverse impact is expected to be amplified in the future due to the current climate change. Here, we analyzed the effects of edaphic, environmental, and host factors on the wheat root microbiomes collected in soils from six regions in Belgium. Amplicon sequencing analysis of unplanted soil and wheat root endosphere samples indicated that the microbial community variations can be significantly explained by soil pH, microbial biomass, wheat genotype, and soil sodium and iron levels. Under drought stress, the biodiversity in the soil decreased significantly, but increased in the root endosphere community, where specific soil parameters seemingly determine the enrichment of bacterial groups. Indeed, we identified a cluster of drought-enriched bacteria that significantly correlated with soil compositions. Interestingly, integration of a functional analysis further revealed a strong correlation between the same cluster of bacteria and β-glucosidase and osmoprotectant proteins, two functions known to be involved in coping with drought stress. By means of this in silico analysis, we identified amplicon sequence variants (ASVs) that could potentially protect the plant from drought stress and validated them in planta. Yet, ASVs based on 16S rRNA sequencing data did not completely distinguish individual isolates because of their intrinsic short sequences. Our findings support the efforts to maintain stable crop yields under drought conditions through implementation of root microbiome analyses.

Characterization of a glucose-stimulated β-glucosidase from Microbulbifer sp. ALW1

Glucose-tolerant and/or glucose-stimulated β-glucosidase is of great interest for its industrial utilization in enzymatic digestion of lignocellulosic biomass for biofuel production. In this study, a new gene of β-glucosidase MaGlu1A was cloned from an alginate-degrading marine bacterium Microbulbifer sp. ALW1. The gene of MaGlu1A encoded a 472-amino acid protein classified into the glycosyl hydrolase family 1 (GH1). The recombinant β-glucosidase was overexpressed and purified from Escherichia coli with a molecular mass of 65.0 kDa. Structure analysis illustrated the catalytic acid/base residue Glu186 and nucleophilic residue Glu370 in the enzyme. MaGlu1A displayed optimal activity at 40 °C and pH 4.5, respectively. It had substrate preference to the aryl-β-glycosidic bonds with glucose, fucose, and galactose moieties, in addition to cellobiose. MaGlu1A demonstrated strong stimulation to the supplemental glucose. Site-directed mutagenesis suggested an essential role of Asn242 in glucose stimulation. The enzymatic characterization of MaGlu1A provides general information about its catalytic properties facilitating its practical applications.

Glucosidase Inhibitors Screening in Microalgae and Cyanobacteria Isolated from the Amazon and Proteomic Analysis of Inhibitor Producing Synechococcus sp. GFB01

Microalgae and cyanobacteria are good sources for prospecting metabolites of biotechnological interest, including glucosidase inhibitors. These inhibitors act on enzymes related to various biochemical processes; they are involved in metabolic diseases, such as diabetes and Gaucher disease, tumors and viral infections, thus, they are interesting hubs for the development of new drugs and therapies. In this work, the screening of 63 environmental samples collected in the Brazilian Amazon found activity against β-glucosidase, of at least 60 min, in 13.85% of the tested extracts, with Synechococcus sp. GFB01 showing inhibitory activity of 90.2% for α-glucosidase and 96.9% against β-glucosidase. It was found that the nutritional limitation due to a reduction in the concentration of sodium nitrate, despite not being sufficient to cause changes in cell growth and photosynthetic apparatus, resulted in reduced production of α and β-glucosidase inhibitors and differential protein expression. The proteomic analysis of cyanobacteria isolated from the Amazon is unprecedented, with this being the first work to evaluate the protein expression of Synechococcus sp. GFB01 subjected to nutritional stress. This evaluation helps to better understand the metabolic responses of this organism, especially related to the production of inhibitors, adding knowledge to the industrial potential of these cyanobacterial compounds.

Secretome characterization of the lignocellulose-degrading fungi Pycnoporus sanguineus and Ganoderma resinaceum growing on Panicum prionitis biomass

C4 grasses are common species in rangelands around the world and represent an attractive option for second-generation biofuel production. Although they display high polysaccharide content and reach great levels of biomass accumulation, there is a major technical issue to be addressed before they can be used for bioethanol industrial production: lignin removal. Concerning this, Pycnoporus and Ganoderma fungal genera have been highlighted due to their ability to hydrolyze lignocellulose in biological pretreatments. Our goals here were to evaluate the pretreatment efficiency using the secretome of species from Pycnoporus and Ganoderma spp. harvested from a glucose-free inductive medium (using a C4 grass) and to identify the fungal enzymatic activities responsible for the lignin degradation and glucose release. Our results show that P. sanguineus secretome exhibits a higher activity of lignocellulolytic enzymes such as cellulases, xylanases, laccases, and manganese peroxidases compared with that from G. resinaceum. Interestingly, zymograms in the presence of 2 M glucose suggest that a β-glucosidase isoform from P. sanguineus could be glucose tolerant. The proteomic approach carried out allowed the identification of 73 and 180 different proteins in G. resinaceum and P. sanguineus secretomes, respectively, which were functionally classified in five main categories and a miscellaneous group. These results open new avenues for future experimental work that lead to a deeper comprehension and a greater application of the mechanisms underlying lignocellulosic biomass degradation.

Highly enhanced activity and stability via affinity induced immobilization β-glucosidase from Aspergillus niger onto amino-based silica for the biotransformation of ginsenoside Rb1

In this study, an enzyme immobilization method for the effective biotransformation of ginsenoside Rb1 to impart activity and stability was developed. Using a hydrolase enzyme model, β-glucosidase from Aspergillus niger, immobilization within chemically affinity-linked amino-based silica provided an immobilization efficiency 5.86-fold higher than that of free enzyme. Compared with the free enzyme, the immobilized enzyme functioned optimally at a wider pH range and had higher thermostability. The optimum pH for the free and immobilized enzymes was 5.5. The optimal reaction temperature of the immobilized enzyme was 45 °C, which was 5 °C higher than that of the free enzyme. The Michaelis constant (K_m) values before and after immobilization were 0.482 mmol•L^-1 and 0.387 mmol•L^-1, respectively. The catalytic rate (K_cat) for the immobilized and free enzymes was 22.269 mmol•L^-1and 8.800 mmol•L^-1, respectively, and the catalytic efficiency (K_cat/K_m) activity of the immobilized enzyme was 3.30-fold higher than that of the free enzyme. The immobilized enzyme could preserve 97 % of the activity after 45 cycles of repeated use. The high catalytic activity and significant operational stability are beneficial for industrial applications.

In through the out door: Biochemical mechanisms affecting flavonoid glycoside catabolism in plants

Plants are the sole source of flavonoids, a chemical category that includes flavonols. For the most part, flavonols occur as glycosides with numerous postulated biological roles in plants, including photoprotection, modulation of hormone translocation, and sequestration of reactive oxygen species. Flavonol glycosides are often considered as dead-end metabolites because related flavonoids (i.e., anthocyanins) occur in terminal tissues such as flowers and fruit, but recent evidence points to their turnover in planta, including developing photosynthetic tissues. Although microbial degradation pathways for flavonol glycosides of plant origin are well described, plant catabolic pathways are little studied by comparison. This review will address our current understanding of biochemical processes leading to the loss of flavonol glycosides in plants, with a specific emphasis on the evidence for flavonol-specific β-glucosidases. Complete elucidation of these catabolic pathways is dependent on the identification of regiospecific modifying steps, including enzymes associated with the hydrolysis of rhamnosylated flavonols, as well as flavonol peroxidation and their encoding genes. Herein, we highlight challenges for the identification of hypothetical plant α-rhamnosidases and peroxidases involved in flavonol glycoside degradation, and the potential biological role of this catabolism in mitigating oxidative stress in developing and postharvest plant tissues.

Citric acid and enzyme-assisted modification of flavonoids from celery (Apium graveolens) extract and their anti-inflammatory activity in HMC-1.2 cells

Apium graveolens (celery) of the family Apiaceae contains bioactive compounds including luteolin and apigenin. The purpose of this study was to increase the extraction yield of apigenin and luteolin in celery extract using green technology and to evaluate their biological activities. The results showed that CA and β-glucosidase-assisted celery extraction transformed apiin in the celery to apigenin with an increase in luteolin concentration. The CA and β-glucosidase-treated celery extract (CAGE) improved the anti-inflammatory properties of celery extract by inhibiting the expression and production of inflammatory cytokines (IL-6, IL-8, IL-31, and TNF-α) in IL-33-stimulated mast cells (HMC-1.2 cells). Their mechanism of action was tied to the inhibition of ERK, JNK, IKKα, IκBα, and NF-κB activation by CAGE in the stimulated cells. In conclusion, CA and enzyme treatment can be considered as a useful biotechnology tool for the improvement of bioactive compounds in celery and hence improve on their bioactivity. PRACTICAL APPLICATIONS: Apium graveolens commonly called celery is an edible agricultural product cultivated throughout the world and known as a "superfood." Celery contains bioactive compounds including apigenin and luteolin that contribute to their described biological activities. However, extracting celery using normal extraction procedures such as hot water and ethanol methods yields only a small amount of apigenin and luteolin. In the present study, we introduced an eco-friendly method using citric and β-glucosidase to obtain apigenin and luteolin-rich celery extract with improved anti-inflammatory activities. The present work will spark studies on the conversion of less biologically active compounds in functional food materials to more active compounds using CA and β-glucosidase, and the development of functional food with specifically enriched bioactive substances at the industrial levels.

Biotransformation of Polyphenols in Apple Pomace Fermented by β-Glucosidase-Producing Lactobacillus rhamnosus L08

Apple pomace, the main by-product in apple processing, is a cheap source of bioactive compounds that could be used in the food industry. However, the value of this by-product is still far from being fully realized. In this study, 11 strains of Lactobacillus strains were assayed for β-glucosidase activity, and only Lactobacillus rhamnosus L08 (L. rhamnosus L08) showed high cell-membrane associated β-glucosidase activity. We then evaluated the effects of fermentation of apple pomace using the selected strain, focusing on the biotransformation of polyphenols and antioxidant capacity. We found that L. rhamnosus L08 fermentation significantly reduced the contents of quercitrin and phlorizin in apple pomace, while increasing the contents of quercetin and phloretin. The contents of gallic acid, epicatechin acid, caffeic acid, and ferulic acid were also increased in apple pomace after fermentation. In addition, the antioxidant activities of apple pomace were enhanced during fermentation, based on the bioconversion of phenolic profiles. Our results demonstrate that lactic acid bacteria fermentation is a promising approach to enhance the bioactivity of phenolic compounds in apple pomace. Moreover, this study demonstrates that, as a valuable processing by-product with bioactive components, apple pomace can be used in the food industry to provide economic benefits.

β-Glucosidase and β-Galactosidase-Mediated Transglycosylation of Steviol Glycosides Utilizing Industrial Byproducts

Stevia rebaudiana Bertoni is a plant cultivated worldwide due to its use as a sweetener. The sweet taste of stevia is attributed to its numerous steviol glycosides, however, their use is still limited, due to their bitter aftertaste. The transglycosylation of steviol glycosides, aiming at the improvement of their taste, has been reported for many enzymes, however, glycosyl hydrolases are not extensively studied in this respect. In the present study, a β-glucosidase, MtBgl3a, and a β-galactosidase, TtbGal1, have been applied in the transglycosylation of two steviol glycosides, stevioside and rebaudioside A. The maximum conversion yields were 34.6 and 33.1% for stevioside, while 25.6 and 37.6% were obtained for rebaudioside A conversion by MtBgl3a and TtbGal1, respectively. Low-cost industrial byproducts were employed as sugar donors, such as cellulose hydrolyzate and acid whey for TtbGal1- and MtBgl3a- mediated bioconversion, respectively. LC-HRMS analysis identified the formation of mono- and di- glycosylated products from stevioside and rebaudioside A. Overall, the results of the present work indicate that both biocatalysts can be exploited for the design of a cost-effective process for the modification of steviol glycosides.

Electrochemical microgap immunosensors for selective detection of pathogenic Aspergillus niger

Aspergillus niger (A. niger) is a well-known allergenic, harmful fungus in the indoor environment that can cause asthmatic symptoms and atopy. Previous immunosensing approach suffers from an insufficient detection limit, mainly because there are no techniques for target amplification. We report an electrochemical immunosensor that selectively quantifies the A. niger based on the detection of extracellular proteins by using a specific interaction with antibody. The sensor was designed to show a decrease in redox current upon binding of the antigens secreted from A. niger onto an antibody-immobilized surface between the interdigitated electrodes. The extracellular proteins were profiled by LC-MS/MS to identify the antigens existing in the A. niger solution. Since the targets of the sensor are the proteins, its sensitivity and selectivity remain almost intact even after filtration of the spores. It was also found that the use of secretion promoter in the sampling stage greatly improved the sensor's limit of detection (LOD) for the spores. By this, the LOD was lowered by a few orders of magnitude so as to reach the value as low as ~10¹ spores/mL.

Analysis of Populus glycosyl hydrolase family I members and their potential role in the ABA treatment and drought stress response

Glycoside hydrolase family 1 (GH1) β-glucosidases (BGLUs) are encoded by a large number of genes and are involved in many developmental processes and stress responses in plants. Due to their importance in plant growth and development, genome-wide analyses have been conducted in the model plant species Arabidopsis thaliana, rice and maize but not in woody plant species, which have important economic and ecological value. In this study, we systematically analyzed Populus BGLUs (PtBGLUs) and demonstrated the involvement of several genes under stress conditions. Forty-four PtBGLUs were identified in Populus databases; these genes were located on 11 chromosomes, and the proteins of several PtBGLU genes were highly similar. More than 90% of PtBGLUs contain three conserved motifs. Collinearity results showed that 44 PtBGLU genes resulted from 12 tandem and 5 segmental duplication events. Phylogenetic analysis revealed that 128 BGLU genes from Populus trichocarpa, A. thaliana and Oryza sativa could be classified into 4 subgroups and subgroup Ⅱ and Ⅳ were differently having PtBGLUs and AtBGLUs. We further investigated whether several PtBGLUs responded to drought stress and ABA treatment, and the results showed that most of the selected BGLU genes were expressed in response to stress, which is consistent with previous studies involving rice and Arabidopsis homologous genes. Large numbers of stress-, hormone-, and development-related elements in the PtBGLU promoters suggest that BGLU genes may be involved in complex networks. Taken together, our results provide valuable information for an improved understanding of β-glucosidase function in woody plants.

Structural basis for transglycosylation in glycoside hydrolase family GH116 glycosynthases

Glycosynthases are glycoside hydrolase mutants that can synthesize oligosaccharides or glycosides from an inverted donor without hydrolysis of the products. Although glycosynthases have been characterized from a variety of glycoside hydrolase (GH) families, family GH116 glycosynthases have yet to be reported. We produced the Thermoanaerobacterium xylanolyticum TxGH116 nucleophile mutants E441D, E441G, E441Q and E441S and compared their glycosynthase activities to the previously generated E441A mutant. The TxGH116 E441G and E441S mutants exhibited highest glycosynthase activity to transfer glucose from α-fluoroglucoside (α-GlcF) to cellobiose acceptor, while E441D had low but significant activity as well. The E441G, E441S and E441A variants showed broad specificity for α-glycosyl fluoride donors and p-nitrophenyl glycoside acceptors. The structure of the TxGH116 E441A mutant with α-GlcF provided the donor substrate complex, while soaking of the TxGH116 E441G mutant with α-GlcF resulted in cellooligosaccharides extending from the +1 subsite out of the active site, with glycerol in the -1 subsite. Soaking of E441A or E441G with cellobiose or cellotriose gave similar acceptor substrate complexes with the nonreducing glucosyl residue in the +1 subsite. Combining structures with the ligands from the TxGH116 E441A with α-GlcF crystals with that of E441A or E441G with cellobiose provides a plausible structure of the catalytic ternary complex, which places the nonreducing glucosyl residue O4 2.5 Å from the anomeric carbon of α-GlcF, thereby explaining its apparent preference for production of β-1,4-linked oligosaccharides. This functional and structural characterization provides the background for development of GH116 glycosynthases for synthesis of oligosaccharides and glycosides of interest.

Dissecting Cellular Function and Distribution of β-Glucosidases in Trichoderma reesei

Trichoderma reesei has 11 putative β-glucosidases in its genome, playing key parts in the induction and production of cellulase. Nevertheless, the reason why the T. reesei genome encodes so many β-glucosidases and the distinct role each β-glucosidase plays in cellulase production remain unknown. In the present study, the cellular function and distribution of 10 known β-glucosidases (CEL3B, CEL3E, CEL3F, CEL3H, CEL3J, CEL1A, CEL3C, CEL1B, CEL3G, and CEL3D) were explored in T. reesei, leaving out BGL1 (CEL3A), which has been well investigated. We found that the overexpression of cel3b or cel3g significantly enhanced extracellular β-glucosidase production, whereas the overexpression of cel1b severely inhibited cellulase production by cellulose, resulting in nearly no growth of T. reesei. Four types of cellular distribution patterns were observed for β-glucosidases in T. reesei: (i) CEL3B, CEL3E, CEL3F, and CEL3G forming clearly separated protein secretion vesicles in the cytoplasm; (ii) CEL3H and CEL3J diffusing the whole endomembrane as well as the cell membrane with protein aggregation, like a reticular network; (iii) CEL1A and CEL3D in vacuoles; (iv) and CEL3C in the nucleus. β-glucosidases CEL1A, CEL3B, CEL3E, CEL3F, CEL3G, CEL3H, and CEL3J were identified as extracellular, CEL3C and CEL3D as intracellular, and CEL1B as unknown. The extracellular β-glucosidases CEL3B, CEL3E, CEL3F, CEL3H, and CEL3G were secreted through a tip-directed conventional secretion pathway, and CEL1A, via a vacuole-mediated pathway that was achieved without any signal peptide, while CEL3J was secreted via an unconventional protein pathway bypassing the endoplasmic reticulum (ER) and Golgi.

Droplet-Based Microfluidic High Throughput Screening of Corynebacterium glutamicum for Efficient Heterologous Protein Production and Secretion

With emerging interests in heterologous production of proteins such as antibodies, growth factors, nanobodies, high-quality protein food ingredients, etc. the demand for efficient production hosts increases. Corynebacterium glutamicum is an attractive industrial host with great secretion capacity to produce therapeutics. It lacks extracellular protease and endotoxin activities and easily achieves high cell density. Therefore, this study focuses on improving protein production and secretion in C. glutamicum with the use of droplet-based microfluidic (DBM) high throughput screening. A library of C. glutamicum secreting β-glucosidase was generated using chemical mutagenesis coupled with DBM screening of 200,000 mutants in just 20 min. Among 100 recovered mutants, 16 mutants exhibited enhanced enzyme secretion capacity, 13 of which had unique mutation profiles. Whole-genome analysis showed that approximately 50–150 SNVs had occurred on the chromosome per mutant. Functional enrichment analysis of genes with non-synonymous mutations showed overrepresentation of genes involved in protein synthesis and secretion relevant biological processes, such as DNA and ribosome RNA synthesis, protein secretion and energy turnover. Two mutants JCMT1 and JCMT8 exhibited the highest secretion with a six and a fivefold increase in the β-glucosidase activity in the supernatant, respectively, relative to the reference strain JC0190. After plasmid curing, a new plasmid with the gene encoding α-amylase was cloned into these two mutants. The new strains SB024 and SB025 also exhibited a five and a sixfold increase in α-amylase activity in the supernatant, respectively, relative to the reference strain SB023. The results demonstrate how DBM screening can serve as a powerful development tool to improve cell factories for the production and secretion of heterologous proteins.

Characterization of the β-Glucosidase activity in indigenous yeast isolated from wine regions in China

β-glucosidase is a pivotal enzyme that hydrolyzes bound volatile aromatic compounds. However, the activity of β-glucosidase in winemaking and the mechanism by which it affects the flavor and taste of wines have not been fully investigated. In this study, we profiled the characteristics of β-glucosidase derived from wine-related yeasts isolated from different wine-making regions in China, and analyzed the enzyme activity from different parts of the cells under aerobic and anaerobic conditions. A total of 56 strains of wine-related yeasts producing β-glucosidases were screened using the YNB-C medium (YNB 6.7 g L^-1 , cellobiose 5 g L^-1 , pH 5.0). We found that strain Clavispora lusitaniae C117 produced the highest enzyme activity (152.39 µmol pNP ml^-1 h^-1 ). In most strains, β-glucosidase were located in whole cells (periplasmic space) and permeabilized cells (intracellular). The non-Saccharomyces species had the highest enzymatic activity in a strain-dependent manner. Under aerobic conditions, C. lusitaniae C117, Hanseniaspora guilliermondii A27-3-4, Metschnikowia pulcherrima F-1-6, and Pichia anomala C84 had the highest β-glucosidase activity. We further investigated the β-glucosidase activity during the wine fermentation and the effects of sugar, pH, temperature, and ethanol on the enzyme activities of P. anomala C84 and commercial Saccharomyces yeast strains RC212 and VL1. The presence of fructose, glucose, and sucrose strongly inhibited enzyme activity. Similarly, low pH and low temperature inhibited the activity of β-glucosidase, whereas ethanol promoted enzyme activity. Our findings provide a theoretical basis on understanding the different yeast characteristics of β-glucosidase and their potential application for further improving wine aroma complexity.

[Relationships between stoichiometric characteristics of soil enzymatic activities and environmental factors in parallel valleys of western Yunnan, China.]

The valleyes of Hengduan Mountains contain the landscapes with high heterogeneity as well as high diversity of climate and vegetation types. To explore the soil cycling of four elements (C, N, P, S) across the parallel valleys of Nujiang River, Lancang River, Jinsha River and Yuanjiang River in western Yunnan, we collected top soils (0-10 cm) in forests, grasslands, and croplands. The activities of soil enzymes, including β-glucosidase (BG), β-N-acetylglucosaminidase (NAG), acid phosphatase (AP), and sulfatase (SU), which drive the soil C, N, P and S cycling, were determined. We analyzed the relationships of soil enzymatic activities and their stoichiometric characteristics with environmental factors. The activities of both AP and NAG had significant difference among different basins and different land types. The activities of AP, BG, NAG and SU were significantly positively related with each other. From southeast to northwest, the activities of BG, NAG, and SU increased with the altitude. Across all basins, the ecoenzymatic ratios of soils always ranked as AP:SU > BG:SU > NAG:SU > BG:NAG > BG:AP > NAG:AP. Compared with forest and grassland soil, cropland soils in each watershed had a higher BG:NAG and a lower NAG:AP (except Yuanjiang River basin). Moreover, AP:SU, BG:SU and NAG:SU of cropland soils were lower than those of forest and grassland in Yuanjiang River basin. However, they were higher than forest and lower than grassland in both Lancang River basin and Jinsha River basin. Soil enzyme activities and enzymatic stoichiometry were affected by physicochemical properties of soil, climate, and location, with the most contribution from soil physicochemical properties. Agricultural land use significantly affected the stoichiometry of C:N:P acquiring enzymes in soils by reducing the activity of N-degrading enzymes relative, resulting in the increases of BG:NAG and the decreases of NAG:AP. Agricultural activities had limited effects on other enzymatic stoichiometries.

Study on the diversity of non-Saccharomyces yeasts in Chinese wine regions and their potential in improving wine aroma by β-glucosidase activity analyses

This work investigated the diversity of non-Saccharomyces yeasts in main Chinese wine producing area, and discuss their potential in wine fermentation through analyzing their β-glucosidase activity. Grapes from 44 vineyards of 9 regions were detected and a total of 395 non-Saccharomyces were identified and categorized into 16 genera, 28 species. In which, 85 non-Saccharomyces yeasts were primarily screened based on pNPG method and Bradford method, and then evaluated by β-glucosidase environmental adaptability, substrate affinity and enzyme activity. Two selected strains were then inoculated individually or sequentially with commercial Saccharomyces cerevisiae into Gewürztraminer grape juice to detect the physiochemical indexes by HPLC and aroma compound by HS-SPME/GC-MS-FID. The results showed both non-Saccharomyces sequential inoculations increased the total aroma content, while the Candida glabrata strain D18 significantly increased the typicality and complexity of the floral and fruity aroma in Gewürztraminer wines, demonstrated its potential in wine fermentation.

Unconventional β-Glucosidases: A Promising Biocatalyst for Industrial Biotechnology

β-Glucosidases primarily catalyze removal of terminal glucosyl residues from a variety of glucoconjugates and also perform transglycosylation and reverse hydrolysis. These catalytic properties can be readily exploited for degradation of lignocellulosic biomass as well as for pharmaceutical, food and flavor industries. β-Glucosidases have been either isolated in the native form from the producer organism or recombinantly expressed and gaged for their biochemical properties and substrate specificities. Although almond and Aspergillus niger have been instantly recognizable sources of β-glucosidases utilized for various applications, an intricate pool of novel β-glucosidases from different sources can provide their potent replacements. Moreover, one can envisage the better efficacy of these novel candidates in biofuel and biorefinery industries facilitating efficient degradation of biomass. This article reviews properties of the novel β-glucosidases such as glucose tolerance and activation, substrate specificity, and thermostability which can be useful for their applications in lignocellulose degradation, food industry, and pharmaceutical industry in comparison with the β-glucosidases from the conventional sources. Such β-glucosidases have potential for encouraging white biotechnology.

Effects of Bacillus subtilis and its metabolites on corn silage quality

Cellulolytic micro-organisms are potent silage inoculants that decrease the fibrous content in silage and increase the fibre digestibility and nutritional value of silage. This study aimed to evaluate the effects of Bacillus subtilis CCMA 0087 and its enzyme β-glucosidase on the nutritional value and aerobic stability of corn silage after 30 and 60 days of storage. We compared the results among silage without inoculant (SC) and silages inoculated with B. subtilis 8 log₁₀ CFU per kg forage (SB8), 9 log₁₀ CFU per kg forage (SB9) and 9·84 log₁₀ CFU per kg forage + β-glucosidase enzyme (SBE). No differences were observed in the levels of dry matter, crude protein and neutral detergent fibre due to the different treatments or storage times of the silos. Notably, the population of spore-forming bacteria increased in the SB9-treated silage. At 60 days of ensiling, the largest populations of lactic acid bacteria were found in silages treated with SB8 and SBE. Yeast populations were low for all silages, irrespective of the different treatments, and the presence of filamentous fungi was observed only in the SBE-treated silage. Among all silage treatments, SB9 treatment resulted in the highest aerobic stability.

High Diversity of β-Glucosidase-Producing Bacteria and Their Genes Associated with Scleractinian Corals

β-Glucosidase is a microbial cellulose multienzyme that plays an important role in the regulation of the entire cellulose hydrolysis process, which is the rate-limiting step in bacterial carbon cycling in marine environments. Despite its importance in coral reefs, the diversity of β-glucosidase-producing bacteria, their genes, and enzymatic characteristics are poorly understood. In this study, 87 β-glucosidase-producing cultivable bacteria were screened from 6 genera of corals. The isolates were assigned to 21 genera, distributed among three groups: Proteobacteria, Firmicutes, and Actinobacteria. In addition, metagenomics was used to explore the genetic diversity of bacterial β-glucosidase enzymes associated with scleractinian corals, which revealed that these enzymes mainly belong to the glycosidase hydrolase family 3 (GH3). Finally, a novel recombinant β-glucosidase, referred to as Mg9373, encompassing 670 amino acids and a molecular mass of 75.2 kDa, was classified as a member of the GH3 family and successfully expressed and characterized. Mg9373 exhibited excellent tolerance to ethanol, NaCl, and glucose. Collectively, these results suggest that the diversity of β-glucosidase-producing bacteria and genes associated with scleractinian corals is high and novel, indicating great potential for applications in the food industry and agriculture.

[Heterologous expression of a novel β-glucosidase BglD2 and its application in polydatin-hydrolyzing]

A novel β-glucosidase BglD2 with glucose and ethanol tolerant properties was screened and cloned from the deep-sea bacterium Bacillus sp. D1. The application potential of BglD2 toward polydatin-hydrolyzing was also evaluated. BglD2 exhibited the maximal β-glucosidase activity at 45 °C and pH 6.5. BglD2 maintained approximately 50% of its origin activity after incubation at 30 °C and pH 6.5 for 20 h. BglD2 could hydrolyze a variety of substrates containing β (1→3), β (1→4), and β (1→6) bonds. The activity of β-glucosidase was enhanced to 2.0 fold and 2.3 fold by 100 mmol/L glucose and 150 mmol/L xylose, respectively. BglD2 possessed ethanol-stimulated and -tolerant properties. At 30 °C, the activity of BglD2 enhanced to 1.2 fold in the presence of 10% ethanol and even remained 60% in 25% ethanol. BglD2 could hydrolyze polydatin to produce resveratrol. At 35 °C, BglD2 hydrolyzed 86% polydatin after incubation for 2 h. Thus, BglD2 possessed glucose and ethanol tolerant properties and can be used as the potential candidate of catalyst for the production of resveratrol from polydatin.

Fluorescence spectroscopy and molecular docking analysis of the binding of Lactobacillus acidophilus GIM1.208 β-glucosidase with quercetin glycosides

Lactobacillus acidophilus is an important probiotic. The β-glucosidase produced by L. acidophilus GIM1.208 can transform quercetin glycosides of Rosa roxburghii Tratt to release quercetin and improve the functional activity of raw materials. Understanding the interaction and the characteristics of the two will lay a theoretical foundation for the site-directed transformation and functional application of the catalytic active site of enzymes. In our study, using the heterologously expressed and highly stable, purified L. acidophilus GIM1.208 BGL as the strain, the representative quercetin in β-glucosidase and Rosa roxburghii Tratt was preliminarily predicted and explored using ultraviolet-visible absorption spectroscopy. Fluorescence spectroscopy combined with molecular docking was used to determine the interaction characteristics of the glycoside substrates, rutin (Rut) and isoquercitrin (Iso). Results from molecular docking showed that Asp159, Arg56, Iso294, Phe292, and Gly25 were the main residues of β-glucosidase and Rut. Arg56 was found to be the most crucial residue of β-glucosidase and isoquercitrin; the interaction between Rut and Iso and β-glucosidase was mainly driven by hydrogen bonding. The combined free energy of β-glucosidase and Iso was found to be -182.10 kcal/mol, while that of β-glucosidase and Rut was -32.37 kcal/mol. The results of fluorescence spectroscopy showed that the fluorescence intensity of β-glucosidase decreased with an increase in Rut and Iso concentrations. This interaction made β-glucosidase quench endogenous fluorescence, which was static quenching. The binding constants of Rut and Iso with β-glucosidase were determined to be 0.50×10⁷ and 0.31×10⁷ L/mol, respectively, indicating that rutin had a stronger affinity when interacting with β-glucosidase. These findings were consistent with our prediction results determined using molecular docking studies.

A novel β-glucosidase from a hot-spring metagenome shows elevated thermal stability and tolerance to glucose and ethanol

β-glucosidase causes hydrolysis of β-1,4-glycosidic bond in glycosides and oligosaccharides. It is an industrially important enzyme owing to its potential in biomass processing applications. In this study, computational screening of an extreme temperature aquatic habitat metagenomic resource was done, leading to the identification of a novel gene, bgl_M, encoding a β-glucosidase. The comparative protein sequence and homology structure analyses designated it as a GH1 family β-glucosidase. The bgl_M gene was expressed in a heterologous host, Escherichia coli. The purified protein, Bgl_M, was biochemically characterized for β-glucosidase activity. Bgl_M exhibited noteworthy hydrolytic potential towards cellobiose and lactose. Bgl_M, showed substantial catalytic activity in the pH range of 5.0-7.0 and at the temperature 40 °C-70 °C. The enzyme was found quite stable at 50 °C with a loss of hardly 20% after 40 h of heat exposure. Furthermore, any drastically negative effect was not observed on the enzyme's activity in the presence of metal ions, non-ionic surfactants, metal chelating, and denaturing agents. A significantly high glucose tolerance, retaining 80% relative activity at 1 M, and 40% at 5 M glucose, and ethanol tolerance, exhibiting 80% relative activity in 10% ethanol, enrolled Bgl_M as a promising enzyme for cellulose saccharification. Furthermore, its ability to catalyze the hydrolysis of daidzin and polydatin ascertained it as an admirably suited biocatalyst for enhancement of nutritional values in soya and wine industries.

Structural aspects of β-glucosidase of Myceliophthora thermophila (MtBgl3c) by homology modelling and molecular docking

Cellulases are the enzymes with diverse range of industrial applications. Cellulases degrade cellulose into monomeric glucose units by hydrolysing β-1,4-glycosidic bonds. There are three components of cellulases: a) endoglucanase, b) exoglucanase and c) β-glucosidase which act synergistically in cellulose bioconversion. The cellulases are the third largest industrial enzymes with a great potential in bioethanol production. In this investigation, a β-glucosidase of a thermophilic fungus Myceliophthora thermophila (MtBgl3c) was analysed for its structural characterization using in silico approaches. The protein structure of MtBgl3c is unknown, therefore an attempt has been made to model 3D structure using Modeller 9.23 software. The MtBgl3c protein model generated was validated from Verify 3D and ERRAT scores of 89.37% and 71.25%, respectively derived from SAVES. Using RAMPAGE the Ramachandran plot was generated, which predicted the accuracy of the 3D model with 91.5% amino acid residues in the favored region. The ion binding and N-glycosylation sites were also predicted. The generated model was docked with cellobiose to predict the most favorable binding sites of MtBgl3c. The key amino acid residues involved in cellobiose bonding are Val88, Asp106, Asp287, Tyr255, Arg170, Glu514. The catalytic conserved amino residues of MtBgl3c were identified. The dock score of cellobiose with MtBgl3c is much lower (-6.46 kcal/mol) than that of glucose (-5.61 kcal/mol), suggesting its high affinity for cellobiose. The docking data of MtBgl3c with glucose illustrate its tolerance to glucose. The present study provides insight into structural characteristics of the MtBgl3c which can be further validated by experimental data. Highlights3D structure of β-glucosidase (MtBgl3c) of Myceliophthora thermophila is being proposed based on computational analysesThe amino acid residues Asp106, Asp287, Tyr255, Arg170 and Glu514 have been identified to play catalytically important role in substrate bindingDocking and interaction of MtBgl3c with cellobiose and glucose has been confirmedDocking analysis of MtBgl3c with glucose suggested its glucose toleranceThe data would be useful in engineering enzymes for attaining higher catalytic efficiencyCommunicated by Ramaswamy H. Sarma.

Inhibition of β-glucosidase overcomes gastric cancer chemoresistance through inducing lysosomal dysfunction

OBJECTIVE

The clinical management of gastric cancer still remains challenge due to its poor response to chemotherapy. Better understanding the underlying mechanisms is required for the identification of more comprehensive therapies to overcome chemoresistance in gastric cancer.

MATERIALS AND METHODS

GBA1 level was systematically analyzed in gastric cancer patients before and after chemotherapy, and gastric cancer cells exposed to long-term chemo agent's treatment. The roles of GBA1 and its downstream mechanisms were investigated using pharmacological and genetic approaches.

RESULTS

We observed the time-dependent upregulation of GBA1 expression and enzyme activity in multiple gastric cancer cell lines in response to prolonged exposure of 5-FU. It is noted that this phenomenon was also observed in gastric cancer patients after chemotherapy. Interestingly, no significant differences on GBA1 expression were detected between normal and malignant gastric tissues. These suggest that the predominant role of GBA1 is in the development of gastric cancer chemoresistance rather than tumorigenesis. Functional analysis demonstrated that GBA1 inhibition suppressed gastric cancer growth and survival without affecting migration, and augmented 5-FU's efficacy. Consistently, GBA1 inhibition was active against 5-FU-resistant gastric cancer cells. Mechanism studies showed that GBA1 inhibition led to loss of lysosomal integrity and function in 5-FU-resistant gastric cancer cells.

CONCLUSIONS

We are the first to show that inhibition of β-glucosidase (encoded by GBA1) sensitizes gastric cancer to chemotherapy. Our findings demonstrate the therapeutic value of inhibiting GBA1 in gastric cancer, particularly in those who develop chemoresistance.