Characterization of an unusual cold-active beta-glucosidase belonging to family 3 of the glycoside hydrolases from the psychrophilic isolate Paenibacillus sp. strain C7

Novel glycosidase from Paenibacillus lactis 154 hydrolyzing the 28-O-β-D-glucopyranosyl ester bond of oleanane-type saponins

Oleanane-type ginsenosides are a class of compounds with remarkable pharmacological activities. However, the lack of effective preparation methods for specific rare ginsenosides has hindered the exploration of their pharmacological properties. In this study, a novel glycoside hydrolase PlGH3 was cloned from Paenibacillus lactis 154 and heterologous expressed in Escherichia coli. Sequence analysis revealed that PlGH3 consists of 749 amino acids with a molecular weight of 89.5 kDa, exhibiting the characteristic features of the glycoside hydrolase 3 family. The enzymatic characterization results of PlGH3 showed that the optimal reaction pH and temperature was 8 and 50 °C by using p-nitrophenyl-β-D-glucopyranoside as a substrate, respectively. The Km and kcat values towards ginsenoside Ro were 79.59 ± 3.42 µM and 18.52 s-1, respectively. PlGH3 exhibits a highly specific activity on hydrolyzing the 28-O-β-D-glucopyranosyl ester bond of oleanane-type saponins. The mechanism of hydrolysis specificity was then presumably elucidated through molecular docking. Eventually, four kinds of rare oleanane-type ginsenosides (calenduloside E, pseudoginsenoside RP1, zingibroside R1, and tarasaponin VI) were successfully prepared by biotransforming total saponins extracted from Panax japonicus. This study contributes to understanding the mechanism of enzymatic hydrolysis of the GH3 family and provides a practical route for the preparation of rare oleanane-type ginsenosides through biotransformation. KEY POINTS: • The glucose at C-28 in oleanane-type saponins can be directionally hydrolyzed. • Mechanisms to interpret PlGH3 substrate specificity by molecular docking. • Case of preparation of low-sugar alternative saponins by directed hydrolysis.

Structural and functional insights of a cold-adaptive β-glucosidase with very high glucose tolerance from Microbacterium sp. CIAB417

A gene glu1 (WP_243232135.1) coding for β-glucosidase from the genome of Microbacterium sp. CIAB417 was characterized for its cold adaptive nature and tolerance to high levels of glucose and ethanol. The phylogenetic analysis suggested the close association of glu1 with a similar gene from a mesophilic bacterium Microbacterium indicum. The purified recombinant GLU1 displayed its optimal activity and stability at pH 5 and temperature 30ᴼC. Additionally, the presence of L3 loop in GLU1 suggested its cold adaptive nature. The glucose tolerant Gate keeper residues (Leu 174 & Trp 169) with a distance of ∼ 6.953 Å between them was also predicted in GLU1. The GLU1 enzyme showed ≥ 95% and ≥ 40% relative activity in the presence of 5 M glucose and 20% ethanol. The V_max, Km, and K_cat values of GLU1 for cellobiose substrate were observed to be 45.22 U/mg, 3.5 mM, and 41.0157 s^-1, respectively. The GLU1 was found to be highly efficient in hydrolysis of celloologosaccharides (C2-C5), lactose and safranal picrocrocin into glucose. Hence, cold adaptive GLU1 with very high glucose and ethanol tolerance could be very useful in bio-refinery, dairy, and flavor industries.

A shotgun approach to explore the bacterial diversity and a brief insight into the glycoside hydrolases of Samiti lake located in the Eastern Himalayas

BACKGROUND

The Himalayas have always been an enigma and, being biodiversity hotspots, are considered extremely important from an ecological point of view. Recent advances in studies regarding high-altitude lakes have garnered relevant importance as these habitats could harbor potential psychrophilic and psychrotrophic microbes with bio-prospective applications. Contemplating the above scenario, the present study has been undertaken to understand the diversity and the functional capacities of the microbes thriving in this lake.

RESULTS

In our present study on Samiti Lake, the abundance of Proteobacteria as the major phylum was seen in both the soil and water samples. Incase of the ABSLW (water) and ABS1 (soil) sample, 148,066 and 239,754 predicted genes, were taken for functional analysis. The KEGG analysis showed that ABSLW and ABS1 had 122,911 and 160,268, genes assigned to KO terms respectively. Whereas in case of COG functional analysis, 104,334 and 130,191 genes were assigned to different COG classes for ABSLW and ABS1 respectively. Further, on studying the glycoside hydrolases, an abundance of GH13, GH2, GH3, GH43, and GH23 in both the soil and water samples were seen.

CONCLUSION

Our study has provided a comprehensive report about the bacterial diversity and functional capacities of microbes thriving in Samiti Lake.  It has also thrown some light on the occurrence of glycoside hydrolases in this region, as they have numerous biotechnological applications in different sectors.

Biotechnological potential of psychrophilic microorganisms as the source of cold-active enzymes in food processing applications

Microorganisms striving in extreme environments and exhibiting optimal growth and reproduction at low temperatures, otherwise known as psychrophilic microorganisms, are potential sources of cold-active enzymes. Owing to higher stability and cold activity, these enzymes are gaining enormous attention in numerous industrial bioprocesses. Applications of several cold-active enzymes have been established in the food industry, e.g., β-galactosidase, pectinase, proteases, amylases, xylanases, pullulanases, lipases, and β-mannanases. The enzyme engineering approaches and the accumulating knowledge of protein structure and function have made it possible to improve the catalytic properties of interest and express the candidate enzyme in a heterologous host for a higher level of enzyme production. This review compiles the relevant and recent information on the potential uses of different cold-active enzymes in the food industry.

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.

Optimization of extracellular ethanol-tolerant β-glucosidase production from a newly isolated Aspergillus sp. DHE7 via solid state fermentation using jojoba meal as substrate: purification and biochemical characterization for biofuel preparation

BACKGROUND

The increasing demand and the continuous depletion in fossil fuels have persuaded researchers to investigate new sources of renewable energy. Bioethanol produced from cellulose could be a cost-effective and a viable alternative to petroleum. It is worth note that β-glucosidase plays a key role in the hydrolysis of cellulose and therefore in the production of bioethanol. This study aims to investigate a simple and standardized method for maximization of extracellular β-glucosidase production from a novel fungal isolate under solid-state fermentation using agro-industrial residues as the sole source of carbon and nitrogen. Furthermore, purification and characterization of β-glucosidase were performed to determine the conditions under which the enzyme displayed the highest performance.

RESULTS

A fungus identified genetically as a new Aspergillus sp. DHE7 was found to exhibit the highest extracellular β-glucosidase production among the sixty fungal isolates tested. Optimization of culture conditions improved the enzyme biosynthesis by 2.1-fold (174.6 ± 5.8 U/g of dry substrate) when the fungus grown for 72 h at 35 °C on jojoba meal with 60% of initial substrate moisture, pH 6.0, and an inoculum size of 2.54 × 107 spores/mL. The enzyme was purified to homogeneity through a multi-step purification process. The purified β-glucosidase is monomeric with a molecular mass of 135 kDa as revealed by the SDS-PAGE analysis. Optimum activity was observed at 60 °C and pH of 6.0, with a remarkable pH and thermal stability. The enzyme retained about 79% and 53% of its activity, after 1 h at 70 °C and 80 °C, respectively. The purified β-glucosidase hydrolysed a wide range of substrates but displaying its greater activity on p-nitrophenyl-β-D-glucopyranoside and cellobiose. The values of Km and Vmax on p-nitrophenyl β-D-glucopyranoside were 0.4 mM and 232.6 U/mL, respectively. Purified β-glucosidase displayed high catalytic activity (improved by 25%) in solutions contained ethanol up to 15%.

CONCLUSION

β-glucosidase characteristics associated with its ability to hydrolyse cellobiose, underscore its utilization in improving the quality of food and beverages. In addition, taking into consideration that the final concentration of ethanol produced by the conventional methods is about 10%, suggests its use in ethanol-containing industrial processes and in the saccharification processes for bioethanol production.

A Novel Glucose-Tolerant GH1 β-Glucosidase and Improvement of Its Glucose Tolerance Using Site-Directed Mutation

A novel GH1 β-glucosidase gene (bgla) from marine bacterium was sequenced and expressed in Escherichia coli. After purification by Ni²⁺ affinity chromatography, the recombinant protein was characterized. The purified recombinant enzyme showed maximum activity at 40 °C, pH 7.5 and was stable between temperatures that range from 4 to 30 °C and over the pH range of 6-10. The enzyme displayed a high tolerance to glucose and maximum stimulation at the presence of 100 mM glucose. To improve glucose tolerance of the enzyme, a site-directed mutation (f171w) was introduced into β-glucosidase. The recombinant F171W showed a higher glucose tolerance than the wild type and maintained more than 40% residual activity at the presence of 4 M glucose. Additionally, the recombinant enzymes showed notable tolerance to ethanol. These properties suggest the enzymes may have potential applications for the fermentation of lignocellulosic sugars and the production of biofuels.

Extremophile - An Adaptive Strategy for Extreme Conditions and Applications

The concurrence of microorganisms in niches that are hostile like extremes of temperature, pH, salt concentration and high pressure depends upon novel molecular mechanisms to enhance the stability of their proteins, nucleic acids, lipids and cell membranes. The structural, physiological and genomic features of extremophiles that make them capable of withstanding extremely selective environmental conditions are particularly fascinating. Highly stable enzymes exhibiting several industrial and biotechnological properties are being isolated and purified from these extremophiles. Successful gene cloning of the purified extremozymes in the mesophilic hosts has already been done. Various extremozymes such as amylase, lipase, xylanase, cellulase and protease from thermophiles, halothermophiles and psychrophiles are of industrial interests due to their enhanced stability at forbidding conditions. In this review, we made an attempt to point out the unique features of extremophiles, particularly thermophiles and psychrophiles, at the structural, genomic and proteomic levels, which allow for functionality at harsh conditions focusing on the temperature tolerance by them.

Possible role of β-galactosidase in rheumatoid arthritis

Objective: To investigate the potential role of β-galactosidase in altering immunoglobulin G (IgG) galactosylation in serum of rheumatoid arthritis (RA).Methods: The expression level and activity of β-galactosidase in serum and CD 19⁺ B cells were measured by enzyme-linked immune sorbent assay (ELISA). The effect of β-galactosidase on the N-glycan changes in serum from mice intravenously treated with β-galactosidase was observed by linear ion-trap quadrupole-electrospray ionization mass spectrometry (LTQ-ESI-MS). We established a collagen-induced arthritis (CIA) rat model to explore the biological function of β-galactosidase in RA.Results: The expression level of β-galactosidase in serum of 32 patients was elevated when compared with those of 30 healthy controls. The activity and expression level of β-galactosidase in CD19⁺ B cells from RA patients was higher than those from healthy controls. The ratio of m/z 1142/937 was reduced in mice treated with β-galactosidase when compared with normal mice. We found that β-galactosidase was implicated in the development of inflammation by affecting body weight and elevating the expression level of interleukin-6, tumor necrosis factor-α, and rheumatoid factor in the serum.Conclusions: Our results suggested the high level of β-galactosidase in B cells and serum of RA patients and revealed that altered β-galactosidase may be implicated in the progression of inflammation.

The Statistical Optimisation of Recombinant β-glucosidase Production through a Two-Stage, Multi-Model, Design of Experiments Approach

β-glucosidases are a class of enzyme that are widely distributed in the living world, with examples noted in plants, fungi, animals and bacteria. They offer both hydrolysis and synthesis capacity for a wide range of biotechnological processes. However, the availability of native, or the production of recombinant β-glucosidases, is currently a bottleneck in the widespread industrial application of this enzyme. In this present work, the production of recombinant β-glucosidase from Streptomyces griseus was optimised using a Design of Experiments strategy, comprising a two-stage, multi-model design. Three screening models were comparatively employed: Fractional Factorial, Plackett-Burman and Definitive Screening Design. Four variables (temperature, incubation time, tryptone, and OD600 nm) were experimentally identified as having statistically significant effects on the production of S.griseus recombinant β-glucosidase in E. coli BL21 (DE3). The four most influential variables were subsequently used to optimise recombinant β-glucosidase production, employing Central Composite Design under Response Surface Methodology. Optimal levels were identified as: OD600 nm, 0.55; temperature, 26 °C; incubation time, 12 h; and tryptone, 15 g/L. This yielded a 2.62-fold increase in recombinant β-glucosidase production, in comparison to the pre-optimised process. Affinity chromatography resulted in homogeneous, purified β-glucosidase that was characterised in terms of pH stability, metal ion compatibility and kinetic rates for p-nitrophenyl-β-D-glucopyranoside (pNPG) and cellobiose catalysis.

Overexpression and characterization of a novel cold-adapted and salt-tolerant GH1 β-glucosidase from the marine bacterium Alteromonas sp. L82

A novel gene (bgl) encoding a cold-adapted β-glucosidase was cloned from the marine bacterium Alteromonas sp. L82. Based on sequence analysis and its putative catalytic conserved region, Bgl belonged to the glycoside hydrolase family 1. Bgl was overexpressed in E. coli and purified by Ni²⁺ affinity chromatography. The purified recombinant β-glucosidase showed maximum activity at temperatures between 25°C to 45°C and over the pH range 6 to 8. The enzyme lost activity quickly after incubation at 40°C. Therefore, recombinant β-glucosidase appears to be a cold-adapted enzyme. The addition of reducing agent doubled its activity and 2 M NaCl did not influence its activity. Recombinant β-glucosidase was also tolerant of 700 mM glucose and some organic solvents. Bgl had a K_m of 0.55 mM, a V_max of 83.6 U/mg, a k_cat of 74.3 s^-1 and k_cat/K_m of 135.1 at 40°C, pH 7 with 4-nitrophenyl-β-D-glucopyranoside as a substrate. These properties indicate Bgl may be an interesting candidate for biotechnological and industrial applications.

Characterization of a β-glucosidase from Paenibacillus species and its application for succinic acid production from sugarcane bagasse hydrolysate

In this study, a β-glucosidase from Paenibacillus sp. M1 was expressed in E. coli BL21(DE3), purified and characterized. The specific activity of purified BglA was 137.64U·mg^-1 protein with optimal temperature and pH of 50°C and 6.0. Furthermore, BglA shows excellent adaption to various environmental factors such as temperature, pH and metal ions. Engineered E. coli Suc260 was further reconstructed by overexpressing the β-glucosidase for achieving direct cellobiose utilization, which could efficiently utilize the pretreated sugarcane bagasses hydrolysate (SBH) consisting of 25.30g·L^-1 cellobiose, 9.70g·L^-1 glucose, 5.90g·L^-1 arabinose and 7.10g·L^-1 xylose. As a result, 26.50g·L^-1 and 24.30g·L^-1 succinic acid were produced by strain Suc260(pTbglA) from cellobiose and SBH with corresponding yields of 88.30% and 89.20% using dual-phase fermentation, respectively. This study indicated that incomplete enzymatic hydrolysate of SCB will be a potential feedstock for succinic acid production.

Insight into the bacterial diversity of fermentation woad dye vats as revealed by PCR-DGGE and pyrosequencing

The bacterial diversity in fermenting dye vats with woad (Isatis tinctoria L.) prepared and maintained in a functional state for approximately 12 months was examined using a combination of culture-dependent and -independent PCR-DGGE analyses and next-generation sequencing of 16S rRNA amplicons. An extremely complex ecosystem including taxa potentially contributing to both indigo reduction and formation, as well as indigo degradation was found. PCR-DGGE analyses revealed the presence of Paenibacillus lactis, Sporosarcina koreensis, Bacillus licheniformis, and Bacillus thermoamylovorans, while Bacillus thermolactis, Bacillus pumilus and Bacillus megaterium were also identified but with sequence identities lower than 97%. Dominant operational taxonomic units (OTUs) identified by pyrosequencing included Clostridium ultunense, Tissierella spp., Alcaligenes faecalis, Erysipelothrix spp., Enterococcus spp., Virgibacillus spp. and Virgibacillus panthothenicus, while sub-dominant OTUs included clostridia, alkaliphiles, halophiles, bacilli, moderately thermophilic bacteria, lactic acid bacteria, Enterobacteriaceae, aerobes, and even photosynthetic bacteria. Based on the current knowledge of indigo-reducing bacteria, it is considered that indigo-reducing bacteria constituted only a small fraction in the unique microcosm detected in the natural indigo dye vats.

Biochemical characterization of a novel β-galactosidase from Paenibacillus barengoltzii suitable for lactose hydrolysis and galactooligosaccharides synthesis

A β-galactosidase gene (PbBGal2A) was cloned from Paenibacillus barengoltzii and expressed in Escherichia coli. The in silico analysis of the deduced amino acid sequences revealed that PbBGal2A shared the highest identity of 40% with the characterized glycoside hydrolase (GH) family 2 β-galactosidase from Actinobacillus pleuropneumoniae. The recombinant β-galactosidase (PbBGal2A) was purified with a molecular mass of 124.2kDa on SDS-PAGE. The optimal pH and temperature of PbBGal2A were determined to be pH 7.5 and 45°C, respectively. PbBGal2A was stable within pH 6.0-8.0 and up to 45°C. It completely hydrolyzed the lactose in milk and whey powder solution. In addition, PbBGal2A exhibited high transglycosylation activity and a maximum yield of 47.9% (w/w) for galactooligosaccharides (GOS) production was obtained in 8h at a lactose concentration of 350g/L. These properties make PbBGal2A an ideal candidate for commercial use in the production of lactose-free milk and GOS.

Catabolism of Glycoconjugates in Chronic Otitis Media with Cholesteatoma

Chronic ear disease with cholesteatoma is characterized by an intrusion of keratinizing stratified squamous epithelium into the middle ear manifesting bone resorption at the interface of the perimatrix. The aim of our study was to investigate the markers of a catabolic process associated with several chronic inflammatory states. We assessed the level of catabolism of glycoconjugates in assays of cholesteatoma extracts, quantifying two lysosomal exoglycosidases: alpha-mannosidase (alpha-MAN) and beta-galactosidase (beta-GAL). Cholesteatomas (n = 15) and normal adult postauricular skin served as controls (n = 15) were collected from the patients during surgery owing to chronic otitis media. To assess exoglycosidase activity, release of p-nitrophenol from p-nitrophenol derivatives of alpha-mannose and beta-galactose was used. In 13 of 15 specimens, we observed significantly higher activity of investigated enzymes in cholesteatoma tissue compared with control tissue (postauricular skin). The mean activity of alpha-MAN from the cholesteatoma cells was 1.76 +/- 1.10 nkat/g wet tissue and 0.61 +/- 0.21 nkat/g wet tissue in the control probes. The mean activity of beta-GAL from the cholesteatoma cells was 1.77 +/- 1.07 nkat/g wet tissue and 0.87 +/- 0.20 nkat/g wet tissue in the control probes. Catabolic reactions involving glycoproteins, glycolipids, and proteoglycans may play a role in cholesteatoma-related bone resorption. The present data indicating that the lysosomal exoglycosidases alpha-MAN and beta-GAL are significantly and consistently elevated suggest the need to further correlations assessment between levels of alpha-MAN and beta-GAL and cholesteatoma behavior. Further research should also evaluate the relative importance of these particular exoglycosidases in manifesting bone resorption in considering the spectrum of identified inflammatory mediators.

Molecular cloning and expression of thermostable glucose-tolerant β-glucosidase of Penicillium funiculosum NCL1 in Pichia pastoris and its characterization

A partial peptide sequence of β-glucosidase isoform (Bgl4) of Penicillium funiculosum NCL1 was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The cDNA (bgl4) encoding Bgl4 protein was cloned from P. funiculosum NCL1 RNA by consensus RT-PCR. The bgl4 gene encoded 857 amino acids that contained catalytic domains specific for glycoside hydrolase family 3. The cDNA was over-expressed in Pichia pastoris KM71H and the recombinant protein (rBgl4) was purified with the specific activity of 1,354.3 U/mg. The rBgl4 was a glycoprotein with the molecular weight of ~130 kDa and showed optimal activity at pH 5.0 and 60 °C. The enzyme was thermo-tolerant up to 60 °C for 60 min. The rBgl4 was highly active on aryl substrates with β-glucosidic, β-xylosidic linkages and moderately active on cellobiose and salicin. It showed remarkably high substrate conversion rate of 3,332 and 2,083 μmol/min/mg with the substrates p-nitrophenyl β-glucoside and cellobiose respectively. In addition, the rBgl4 showed tolerance to glucose concentration up to 400 mM. It exhibited twofold increase in glucose yield when supplemented with crude cellulase of Trichoderma reesei Rut-C30 in cellulose hydrolysis. These results suggested that rBgl4 is a thermo- and glucose-tolerant β-glucosidase and is a potential supplement for commercial cellulase in cellulose hydrolysis and thereby assures profitability in bioethanol production.

Cloning, expression and characterization of a pectate lyase from Paenibacillus sp. 0602 in recombinant Escherichia coli

BACKGROUND

Biotechnological applications of microbial pectate lyases (Pels) in plant fiber processing are considered as environmentally friendly. As such, they become promising substitutes for conventional chemical degumming process. Since applications of Pels in various fields are widening, it is necessary to explore new pectolytic microorganisms and enzymes for efficient and effective usage. Here, we describe the cloning, expression, characterization and application of the recombinant Pel protein from a pectolytic bacterium of the genus Paenibacillus in Escherichia coli.

RESULTS

A Pel gene (pelN) was cloned using degenerate PCR and inverse PCR from the chromosomal DNA of Paenibacillus sp. 0602. The open reading frame of pelN encodes a 30 amino acid signal peptide and a 445 amino acid mature protein belonging to the polysaccharide lyase family 1. The maximum Pel activity produced by E. coli in shake flasks reached 2,467.4 U mL⁻¹, and the purified recombinant enzyme exhibits a specific activity of 2,060 U mg⁻¹ on polygalacturonic acid (PGA). The maximum activity was observed in a buffer with 5 mM Ca²⁺ at pH 9.8 and 65°C. PelN displays a half-life of around 9 h and 42 h at 50°C and 45°C, respectively. The biochemical treatment achieved the maximal reduction of percentage weight (30.5%) of the ramie bast fiber.

CONCLUSIONS

This work represents the first study that describes the extracellular expression of a Pel gene from Paenibacillus species in E. coli. The high yield of the extracellular overexpression, relevant thermostability and efficient degumming using combined treatments indicate its strong potential for large-scale industrial production.

A family 3 glycosyl hydrolase of Dickeya dadantii 3937 is involved in the cleavage of aromatic glucosides

Dickeya dadantii is a phytopathogenic bacterium secreting a large array of plant-cell-wall-degrading enzymes that participate in the infection and maceration of the host plant tissue. Sequencing of the D. dadantii 3937 genome predicted several genes encoding potential glycosidases. One of these genes, bgxA, encodes a protein classified in family 3 of glycosyl hydrolases. Inactivation of bgxA and the use of a gene fusion revealed that this gene is not essential for D. dadantii pathogenicity but that it is expressed during plant infection. The bgxA expression is induced in the presence of glycosidic or non-glycosidic aromatic compounds, notably ferulic acid, cinnamic acid, vanillic acid and salicin. The BgxA enzyme has a principal β-d-glucopyranosidase activity and a secondary β-d-xylopyranosidase activity (ratio 70 : 1). This enzyme activity is inhibited by different aromatic glycosides or phenolic compounds, in particular salicin, arbutin, ferulic acid and vanillic acid. Together, the induction effects and the enzyme inhibition suggest that BgxA is mostly involved in the cleavage of aromatic β-glucosides. There is evidence of functional redundancy in the D. dadantii β-glucoside assimilation pathway. In contrast to other β-glucoside assimilation systems, involving cytoplasmic phospho-β-glucosidases, the cleavage of aromatic glucosides in the periplasmic space by BgxA may avoid the release of a toxic phenolic aglycone into the cytoplasm while still allowing for catabolism of the glucose moiety.

Cloning and characterization of a new broadspecific β-glucosidase from Lactococcus sp. FSJ4

A β-glucosidase gene bglX was cloned from Lactococcus sp. FSJ4 by the method of shotgun. The bglX open reading frame consisted of 1,437 bp, encoding 478 amino acids. SDS-PAGE showed a recombinant bglX monomer of 54 kDa. Substrate specificity study revealed that the enzyme exhibited multifunctional catalysis activity against pNPG, pNPX and pNPGal. This enzyme shows higher activity against aryl glycosides of xylose than those of glucose or galactose. The enzyme exhibited the maximal activity at 40 °C, and the optimal pH was 6.0 with pNPG and 6.5 with pNPX as the substrates. Molecular modeling and substrate docking showed that there should be one active center responsible for the mutifuntional activity in this enzyme, since the active site pocket was substantially wide to allow the entry of pNPG, pNPX and pNPGal, which elucidated the structure-function relationship in substrate specificities. Substrate docking results indicated that Glu180 and Glu377 were the essential catalytic residues of the enzyme. The CDOCKER_ENERGY values obtained by substrate docking indicated that the enzyme has higher activity against pNPX than those of pNPG and pNPGal. These observations are in conformity with the results obtained from experimental investigation. Therefore, such substrate specificity makes this β-glucosidase of great interest for further study on physiological and catalytic reaction processes.

Identification and characterization of a Mucilaginibacter sp. strain QM49 β-glucosidase and its use in the production of the pharmaceutically active minor ginsenosides (S)-Rh1 and (S)-Rg2

Here, we isolated and characterized a new ginsenoside-transforming β-glucosidase (BglQM) from Mucilaginibacter sp. strain QM49 that shows biotransformation activity for various major ginsenosides. The gene responsible for this activity, bglQM, consists of 2,346 bp and is predicted to encode 781 amino acid residues. This enzyme has a molecular mass of 85.6 kDa. Sequence analysis of BglQM revealed that it could be classified into glycoside hydrolase family 3. The enzyme was overexpressed in Escherichia coli BL21(DE3) using a maltose binding protein (MBP)-fused pMAL-c2x vector system containing the tobacco etch virus (TEV) proteolytic cleavage site. Overexpressed recombinant BglQM could efficiently transform the protopanaxatriol-type ginsenosides Re and Rg1 into (S)-Rg2 and (S)-Rh1, respectively, by hydrolyzing one glucose moiety attached to the C-20 position at pH 8.0 and 30°C. The Km values for p-nitrophenyl-β-d-glucopyranoside, Re, and Rg1 were 37.0 ± 0.4 μM and 3.22 ± 0.15 and 1.48 ± 0.09 mM, respectively, and the Vmax values were 33.4 ± 0.6 μmol min(-1) mg(-1) of protein and 19.2 ± 0.2 and 28.8 ± 0.27 nmol min(-1) mg(-1) of protein, respectively. A crude protopanaxatriol-type ginsenoside mixture (PPTGM) was treated with BglQM, followed by silica column purification, to produce (S)-Rh1 and (S)-Rg2 at chromatographic purities of 98% ± 0.5% and 97% ± 1.2%, respectively. This is the first report of gram-scale production of (S)-Rh1 and (S)-Rg2 from PPTGM using a novel ginsenoside-transforming β-glucosidase of glycoside hydrolase family 3.

Cloning, overexpression, purification, and characterization of a polyextremophilic β-galactosidase from the Antarctic haloarchaeon Halorubrum lacusprofundi

Background

Halorubrum lacusprofundi is a cold-adapted halophilic archaeon isolated from Deep Lake, a perennially cold and hypersaline lake in Antarctica. Its genome sequencing project was recently completed, providing access to many genes predicted to encode polyextremophilic enzymes active in both extremely high salinity and cold temperatures.

Results

Analysis of the genome sequence of H. lacusprofundi showed a gene cluster for carbohydrate utilization containing a glycoside hydrolase family 42 β-galactosidase gene, named bga. In order to study the biochemical properties of the β-galactosidase enzyme, the bga gene was PCR amplified, cloned, and expressed in the genetically tractable haloarchaeon Halobacterium sp. NRC-1 under the control of a cold shock protein (cspD2) gene promoter. The recombinant β-galactosidase protein was produced at 20-fold higher levels compared to H. lacusprofundi, purified using gel filtration and hydrophobic interaction chromatography, and identified by SDS-PAGE, LC-MS/MS, and ONPG hydrolysis activity. The purified enzyme was found to be active over a wide temperature range (−5 to 60°C) with an optimum of 50°C, and 10% of its maximum activity at 4°C. The enzyme also exhibited extremely halophilic character, with maximal activity in either 4 M NaCl or KCl. The polyextremophilic β-galactosidase was also stable and active in 10–20% alcohol-aqueous solutions, containing methanol, ethanol, n-butanol, or isoamyl alcohol.

Conclusion

The H. lacusprofundi β-galactosidase is a polyextremophilic enzyme active in high salt concentrations and low and high temperature. The enzyme is also active in aqueous-organic mixed solvents, with potential applications in synthetic chemistry. H. lacuprofundi proteins represent a significant biotechnology resource and for developing insights into enzyme catalysis under water limiting conditions. This study provides a system for better understanding how H. lacusprofundi is successful in a perennially cold, hypersaline environment, with relevance to astrobiology.

Partial Characterization of α-Galactosidic Activity from the Antarctic Bacterial Isolate, Paenibacillus sp. LX-20 as a Potential Feed Enzyme Source

An Antarctic bacterial isolate displaying extracellular α-galactosidic activity was named Paenibacillus sp. LX-20 based on 16S rRNA gene sequence analysis. Optimal activity for the LX-20 α-galactosidase occurred at pH 6.0–6.5 and 45°C. The enzyme immobilized on the smart polymer Eudragit L-100 retained 70% of its original activity after incubation for 30 min at 50°C, while the free enzyme retained 58% of activity. The enzyme had relatively high specificity for α-D-galactosides such as p-nitrophenyl-α-galactopyranoside, melibiose, raffinose and stachyose, and was resistant to some proteases such as trypsin, pancreatin and pronase. Enzyme activity was almost completely inhibited by Ag⁺, Hg²⁺, Cu²⁺, and sodium dodecyl sulfate, but activity was not affected by β-mercaptoethanol or EDTA. LX-20 α-galactosidase may be potentially useful as an additive for soybean processing in the feed industry.

Possible role of α-mannosidase and β-galactosidase in larynx cancer

Background

Lysosomal exoglycosidases, such as α-mannosidases (MAN) and β-galactosidases (GAL), are found in different glycoside hydrolase sequence-based families. Considerable research has proved plays the role of MAN, which play a key role in the modification and diversification of hybrid N-glycans, processes with strong cellular links to cancer. Therefore the study aim was to investigate the activities of MAN and GAL in larynx cancer compared to controls.

Material and methods

Larynx cancer (n = 21) and normal healthy tissue (n = 21) were collected from patients during total laryngectomy. A biopsy of macroscopically healthy tissue in the area of the lower 1/3 of omohyoid muscle was taken for frozen sections in each case and these served as controls. The release of p-nitrophenol from p-nitrophenol derivatives of MAN and GAL was used.

Results

In all specimens we observed significantly higher activity of investigated enzymes in larynx cancer compared with controls. The mean release of MAN from activated cells was 3.702 ±1.3245 nkat/g wet tissue compared to controls (1.614 ±0.8220 nkat/g wet tissue). The mean release of GAL from the activated cells was 3.383 ±2.1980 nkat/g wet tissue compared to controls (2.137 ±1.3685 nkat/g wet tissue). Differences in observed activity were statistically significant.

Conclusion

The present data indicate that MAN and GAL are significantly and consistently elevated in larynx cancer growth. It also means that catabolic reactions involving glycoproteins, glycolipids and proteoglycans may play a role in larynx cancer. Further research should also evaluate the relative importance of these particular exoglycosidases in indicating the progress of the disease in considering the spectrum of identified marker mediators.

A highly efficient β-glucosidase from the buffalo rumen fungus Neocallimastix patriciarum W5

BACKGROUND

Cellulose, which is the most abundant renewable biomass on earth, is a potential bio-resource of alternative energy. The hydrolysis of plant polysaccharides is catalyzed by microbial cellulases, including endo-β-1,4-glucanases, cellobiohydrolases, cellodextrinases, and β-glucosidases. Converting cellobiose by β-glucosidases is the key factor for reducing cellobiose inhibition and enhancing the efficiency of cellulolytic enzymes for cellulosic ethanol production.

RESULTS

In this study, a cDNA encoding β-glucosidase was isolated from the buffalo rumen fungus Neocallimastix patriciarum W5 and is named NpaBGS. It has a length of 2,331 bp with an open reading frame coding for a protein of 776 amino acid residues, corresponding to a theoretical molecular mass of 85.1 kDa and isoelectric point of 4.4. Two GH3 catalytic domains were found at the N and C terminals of NpaBGS by sequence analysis. The cDNA was expressed in Pichia pastoris and after protein purification, the enzyme displayed a specific activity of 34.5 U/mg against cellobiose as the substrate. Enzymatic assays showed that NpaBGS was active on short cello-oligosaccharides from various substrates. A weak activity in carboxymethyl cellulose (CMC) digestion indicated that the enzyme might also have the function of an endoglucanase. The optimal activity was detected at 40°C and pH 5 ~ 6, showing that the enzyme prefers a weak acid condition. Moreover, its activity could be enhanced at 50°C by adding Mg2+ or Mn2+ ions. Interestingly, in simultaneous saccharification and fermentation (SSF) experiments using Saccharomyces cerevisiae BY4741 or Kluyveromyces marxianus KY3 as the fermentation yeast, NpaBGS showed advantages in cell growth, glucose production, and ethanol production over the commercial enzyme Novo 188. Moreover, we showed that the KY3 strain engineered with the NpaNGS gene can utilize 2 % dry napiergrass as the sole carbon source to produce 3.32 mg/ml ethanol when Celluclast 1.5 L was added to the SSF system.

CONCLUSION

Our characterizations of the novel β-glucosidase NpaBGS revealed that it has a preference of weak acidity for optimal yeast fermentation and an optimal temperature of ~40°C. Since NpaBGS performs better than Novo 188 under the living conditions of fermentation yeasts, it has the potential to be a suitable enzyme for SSF.

Identification and characterization of psychrotolerant sporeformers associated with fluid milk production and processing

Psychrotolerant spore-forming bacteria represent a major challenge to the goal of extending the shelf life of pasteurized dairy products. The objective of this study was to identify prominent phylogenetic groups of dairy-associated aerobic sporeformers and to characterize representative isolates for phenotypes relevant to growth in milk. Analysis of sequence data for a 632-nucleotide fragment of rpoB showed that 1,288 dairy-associated isolates (obtained from raw and pasteurized milk and from dairy farm environments) clustered into two major divisions representing (i) the genus Paenibacillus (737 isolates, including the species Paenibacillus odorifer, Paenibacillus graminis, and Paenibacillus amylolyticus sensu lato) and (ii) Bacillus (n = 467) (e.g., Bacillus licheniformis sensu lato, Bacillus pumilus, Bacillus weihenstephanensis) and genera formerly classified as Bacillus (n = 84) (e.g., Viridibacillus spp.). When isolates representing the most common rpoB allelic types (ATs) were tested for growth in skim milk broth at 6°C, 6/9 Paenibacillus isolates, but only 2/8 isolates representing Bacillus subtypes, grew >5 log CFU/ml over 21 days. In addition, 38/40 Paenibacillus isolates but only 3/47 Bacillus isolates tested were positive for β-galactosidase activity (including some isolates representing Bacillus licheniformis sensu lato, a common dairy-associated clade). Our study confirms that Paenibacillus spp. are the predominant psychrotolerant sporeformers in fluid milk and provides 16S rRNA gene and rpoB subtype data and phenotypic characteristics facilitating the identification of aerobic spore-forming spoilage organisms of concern. These data will be critical for the development of detection methods and control strategies that will reduce the introduction of psychrotolerant sporeformers and extend the shelf life of dairy products.

Expression and characterization of a cold-active and xylose-stimulated β-glucosidase from Marinomonas MWYL1 in Escherichia coli

The gene encoding a cold-active and xylose-stimulated β-glucosidase of Marinomonas MWYL1 was synthesized and expressed in Escherichia coli. The recombinant enzyme (reBglM1) was purified and characterized. The molecular mass of the purified reBglM1 determined by SDS-PAGE agree with the calculated values (50.6 Da). Optima of temperature and pH for enzyme activity were 40 °C and 7.0, respectively. The enzyme exhibited about 20% activity at 5 °C and was stable over the range of pH 5.5-10.0. The presence of xylose significantly enhanced enzyme activity even at higher concentrations up to 600 mM, with maximal stimulatory effect (about 1.45-fold) around 300 mM. The enzyme is active with both glucosides and galactosides and showed high catalytic efficiency (k (cat) = 500.5 s(-1)) for oNPGlc. These characterizations enable the enzyme to be a promising candidate for industrial applications.

A novel low-temperature-active β-glucosidase from symbiotic Serratia sp. TN49 reveals four essential positions for substrate accommodation

A 2,373-bp full-length gene (bglA49) encoding a 790-residue polypeptide (BglA49) with a calculated mass of 87.8 kDa was cloned from Serratia sp. TN49, a symbiotic bacterium isolated from the gut of longhorned beetle (Batocera horsfieldi) larvae. The deduced amino acid sequence of BglA49 showed the highest identities of 80.1% with a conceptually translated protein from Pantoea sp. At-9b (EEW02556), 38.3% with the identified glycoside hydrolase (GH) family 3 β-glucosidase from Clostridium stercorarium NCBI 11754 (CAB08072), and <15.0% with the low-temperature-active GH 3 β-glucosidases from Shewanella sp. G5 (ABL09836) and Paenibacillus sp. C7 (AAX35883). The recombinant enzyme (r-BglA49) was expressed in Escherichia coli and displayed the typical characteristics of low-temperature-active enzymes, such as low temperature optimum (showing apparent optimal activity at 35°C), activity at low temperatures (retaining approximately 60% of its maximum activity at 20°C and approximately 25% at 10°C). Compared with the thermophilic GH 3 β-glucosidase, r-BglA49 had fewer hydrogen bonds and salt bridges and less proline residues. These features might relate to the increased structure flexibility and higher catalytic activity at low temperatures of r-BglA49. The molecular docking study of four GH 3 β-glucosidases revealed five conserved positions contributing to substrate accommodation, among which four positions of r-BglA49 (R192, Y228, D260, and E449) were identified to be essential based on site-directed mutagenesis analysis.

Biochemical characterization of two novel β-glucosidase genes by metagenome expression cloning

Two novel β-glucosidase genes designated as bgl1D and bgl1E, which encode 172- and 151-aa peptides, respectively, were cloned by function-based screening of a metagenomic library from uncultured soil microorganisms. Sequence analyses indicated that Bgl1D and Bgl1E exhibited lower similarities with some putative β-glucosidases. Functional characterization through high-performance liquid chromatography demonstrated that purified recombinant Bgl1D and Bgl1E proteins hydrolyzed D-glucosyl-β-(1-4)-D-glucose to glucose. Using p-nitrophenyl-β-D-glucoside as substrate, K(m) was 0.54 and 2.11 mM, and k(cat)/K(m) was 1489 and 787 mM(-1) min(-1) for Bgl1D and Bgl1E, respectively. The optimum pH and temperature for Bgl1D was pH 10.0 and 30°C, while the optimum values for Bgl1E were pH 10.0 and 25°C. Bgl1D exhibited habitat-specific characteristics, including higher activity in lower temperature and at high concentrations of AlCl(3) and LiCl. Bgl1D also displayed remarkable activity across a broad pH range (5.5-10.5), making it a potential candidate for industrial applications.

High-level expression of barley beta-D-glucan exohydrolase HvExoI from a codon-optimized cDNA in Pichia pastoris

The native beta-d-glucan exohydrolase isoenzyme ExoI from barley seedlings, designated HvExoI, was the first GH3 glycoside hydrolase, for which a crystal structure was determined. A precise understanding of relationships between structure and function in this enzyme has been gained by structural and enzymatic studies. To allow testing of hypotheses gained from these studies, an efficient system for expression of HvExoI in Pichia pastoris was developed using a codon-optimized cDNA. Protein expression at a temperature of 20 degrees C yielded a recombinant enzyme, designated rHvExoI, which had molecular masses of 70-110 kDa due to heavy glycosylation at Asn221, Asn498 and Asn600, the three sites of N-glycosylation in native HvExoI. Most of the N-linked carbohydrate could be removed from rHvExoI, resulting in N-deglycosylated rHvExoI with a substantially decreased molecular mass of 67 kDa. rHvExoI was able to hydrolyse barley (1,3;1,4)-beta-D-glucan, laminarin and lichenans. The catalytic efficiency value k(cat)/K(M) of rHvExoI with barley (1,3;1,4)-beta-D-glucan was similar to that reported for native HvExoI. Further, laminaribiose, cellobiose and gentiobiose were formed through transglycosylation reactions with 4-nitrophenyl beta-D-glucoside and barley (1,3;1,4)-beta-D-glucan. Overall, the biochemical properties of rHvExoI were similar to those reported for native HvExoI, although differences were seen in thermostabilities and hydrolytic rates of certain beta-linked glucosides.

Directed evolution of a beta-galactosidase from Pyrococcus woesei resulting in increased thermostable beta-glucuronidase activity

We performed directed evolution on a chemically synthesized 1,533-bp recombinant beta-galactosidase gene from Pyrococcus woesei. More than 200,000 variant colonies in each round of directed evolution were screened using the pYPX251 vector and host strain Rosetta-Blue (DE3). One shifted beta-galactosidase to beta-glucuronidase mutant, named YG6762, was obtained after four rounds of directed evolution and screening. This mutant had eight mutated amino acid residues. T29A, V213I, L217M, N277H, I387V, R491C, and N496D were key mutations for high beta-glucuronidase activity, while E414D was not essential because the mutation did not lead to a change in beta-glucuronidase activity. The amino acid site 277 was the most essential because mutating H back to N resulted in a 50% decrease in beta-glucuronidase activity at 37 degrees C. We also demonstrated that amino acid 277 was the most essential site, as the mutation from N to H resulted in a 1.5-fold increase in beta-glucuronidase activity at 37 degrees C. Although most single amino acid changes lead to less than a 20% increase in beta-glucuronidase activity, the YG6762 variant, which was mutated at all eight amino acid sites, had a beta-glucuronidase activity that was about five and seven times greater than the wild-type enzyme at 37 and 25 degrees C, respectively.

Construction of a low-temperature protein expression system using a cold-adapted bacterium, Shewanella sp. strain Ac10, as the host

A recombinant protein expression system working at low temperatures is expected to be useful for the production of thermolabile proteins. We constructed a low-temperature expression system using an Antarctic cold-adapted bacterium, Shewanella sp. strain Ac10, as the host. We evaluated the promoters for proteins abundantly produced at 4 degrees C in this bacterium to express foreign proteins. We used 27 promoters and a broad-host-range vector, pJRD215, to produce beta-lactamase in Shewanella sp. strain Ac10. The maximum yield was obtained when the promoter for putative alkyl hydroperoxide reductase (AhpC) was used and the recombinant cells were grown to late stationary phase. The yield was 91 mg/liter of culture at 4 degrees C and 139 mg/liter of culture at 18 degrees C. We used this system to produce putative peptidases, PepF, LAP, and PepQ, and a putative glucosidase, BglA, from a psychrophilic bacterium, Desulfotalea psychrophila DSM12343. We obtained 48, 7.1, 28, and 5.4 mg/liter of culture of these proteins, respectively, in a soluble fraction. The amounts of PepF and PepQ produced by this system were greater than those produced by the Escherichia coli T7 promoter system.