Characterization of salt-tolerant β-glucosidase with increased thermostability under high salinity conditions from Bacillus sp. SJ-10 isolated from jeotgal, a traditional Korean fermented seafood

Postbiotic potential of Bacillus velezensis KMU01 cell-free supernatant for the alleviation of obesity in mice

Attention toward the preventive effects of postbiotics on metabolic diseases has increased because of greater stability and safety over probiotics. However, studies regarding the bioactive effects of postbiotics, especially from probiotic Bacillus strains, are relatively limited. The anti-obesity effects of the cell-free culture supernatant of Bacillus velezensis KMU01 (CFS-B.vele) were evaluated using high-fat-diet (HFD)-induced mice. HFD-induced mice (n = 8 per group) received equal volumes of (1) CFS-B.vele (114 mg/kg) in PBS, (2) Xenical in PBS, or (3) PBS alone by oral gavage daily for 13 weeks. The results demonstrated that CFS-B.vele changed the gut microbiota and showed anti-obesity effects in HFD-induced obese mice. The elevated Firmicutes/Bacteroidota ratio induced by HFD was decreased in the CFS-B.vele group compared to the other groups (p < 0.05). The CFS-B.vele intervention led to the enrichment of SCFA-producers, such as Roseburia and Eubacterium, in the cecum, suggesting their potential involvement in the amelioration of obesity. Due to these changes, the various obesity-related biomarkers (body weight, fat in tissue, white adipose tissue weight and size, serum LDL-cholesterol level, hepatic lipid accumulation, and adipogenesis/lipogenesis-related gene/protein expression) were improved. Our findings suggest that CFS-B.vele has potential as a novel anti-obesity agent through modulation of the gut microbiota.

Heterologous expression and characterization of salt-tolerant β-glucosidase from xerophilic Aspergillus chevalieri for hydrolysis of marine biomass

A salt-tolerant exo-β-1,3-glucosidase (BGL_MK86) was cloned from the xerophilic mold Aspergillus chevalieri MK86 and heterologously expressed in A. oryzae. Phylogenetic analysis suggests that BGL_MK86 belongs to glycoside hydrolase family 5 (aryl-phospho-β-D-glucosidase, BglC), and exhibits D-glucose tolerance. Recombinant BGL_MK86 (rBGL_MK86) exhibited 100-fold higher expression than native BGL_MK86. rBGL_MK86 was active over a wide range of NaCl concentrations [0%-18% (w/v)] and showed increased substrate affinity for p-nitrophenyl-β-D-glucopyranoside (pNPBG) and turnover number (kcat) in the presence of NaCl. The enzyme was stable over a broad pH range (5.5-9.5). The optimum reaction pH and temperature for hydrolysis of pNPBG were 5.5 and 45 °C, respectively. rBGL_MK86 acted on the β-1,3-linked glucose dimer laminaribiose, but not β-1,4-linked or β-1,6-linked glucose dimers (cellobiose or gentiobiose). It showed tenfold higher activity toward laminarin (a linear polymer of β-1,3 glucan) from Laminaria digitata than laminarin (β-1,3/β-1,6 glucan) from Eisenia bicyclis, likely due to its inability to act on β-1,6-linked glucose residues. The β-glucosidase retained hydrolytic activity toward crude laminarin preparations from marine biomass in moderately high salt concentrations. These properties indicate wide potential applications of this enzyme in saccharification of salt-bearing marine biomass.

Characterization of a novel recombinant halophilic β-glucosidase of Trichoderma harzianum derived from Hainan mangrove

BACKGROUND

β-glucosidase is an important biomass-degrading enzyme and plays a vital role in generating renewable biofuels through enzymatic saccharification. In this study, we analyzed the transcriptome of Trichoderma harzianum HTASA derived from Hainan mangrove and identified a new gene encoding β-glucosidase Bgl3HB. And the biochemically characterization of β-glucosidase activity was performed.

RESULTS

Bgl3HB showed substantial catalytic activity in the pH range of 3.0-5.0 and at temperatures of 40 ℃-60 ℃. The enzyme was found quite stable at 50 ℃ with a loss of only 33.4% relative activity after 240 min of heat exposure. In addition, all tested metal ions were found to promote the enzyme activity. The β-glucosidase activity of Bgl3HB was enhanced by 2.12-fold of its original activity in the presence of 5 M NaCl. Surprisingly, Bgl3HB also showed a remarkable ability to hydrolyze laminarin compared to other measured substrates. Enzyme efficiency was examined in the sugarcane bagasse saccharification processes, in which Bgl3HB with 5 M NaCl worked better supplementing Celluclast 1.5L than the commercial Novozyme 188 ascertained it as an admirably suited biocatalyst for the utilization of agricultural waste. In this work, this is the first report of a halophilic β-glucosidase from Trichoderma harzianum, and represents the β-glucosidase with the highest known NaCl activation concentration. And adding 5 M NaCl could enhance saccharification performance even better than commercial cellulase.

CONCLUSIONS

These results show that Bgl3HB has great promise as a highly stable and highly efficient cellulase with important future applications in the industrial production of biofuels.

Cloning, biochemical characterization and molecular docking of novel thermostable β-glucosidase BglA9 from Anoxybacillus ayderensis A9 and its application in de-glycosylation of Polydatin

This study reports a novel BglA9 gene of 1345 bp encoding β-glucosidase from Anoxybacillus ayderensis A9, which was amplified and expressed in E. coli BL21 (DE3): pLysS cells, purified with Ni-NTA column having molecular weight of 52.6 kDa and was used in the bioconversion of polydatin to resveratrol. The kinetic parameters values using pNPG as substrate were K_m (0.28 mM), V_max (43.8 μmol/min/mg), k_cat (38.43 s^-1) and k_cat/K_m (135.5 s^-1 mM^-1). The BglA9 was active in a broad pH range and had an activity half-life around 24 h at 50 °C. The de-glycosylation efficiency of BglA9 for polydatin was determined by estimating the amount of glucose released after enzymatic reaction by a dinitrosalicylic acid (DNS) assay. The kinetic parameters of BglA9 for polydatin were 5.5 mM, 20.84 μmol/min/mg, 18.28 s^-1and 3.27 s^-1 mM^-1 for K_m, V_max, k_cat, and k_cat/K_m values, respectively. The K_i value for glucose was determined to be 1.7 M. The residues Gln19, His120, Glu355, Glu409, Glu178, Asn222 may play a crucial role in the deglycosylation as revealed by the 3D structure of enzyme docked with polydatin.

Assessment of potential infectivity of human norovirus in the traditional Korean salted clam product "Jogaejeotgal" by floating electrode-dielectric barrier discharge plasma

This study investigated the antiviral effects of floating electrode-dielectric barrier discharge (FE-DBD) plasma treatment (1.1 kV, 43 kHz, N₂ 1.5 m/s, 5-30 min) against human norovirus (HuNoV) GII.4 in Jogaejeotgal Infectivity was assessed using real-time quantitative-PCR (RT-qPCR) following treatment of samples with propidium monoazide (PMA) and sodium lauroyl sarcosinate (Sarkosyl). This study also investigated the effects of FE-DBD plasma treatment on Jogaejeotgal quality (assessed using pH value and Hunter colors). Following inoculation, the average titers of HuNoV GII.4 in Jogaejeotgal significantly (P < 0.05) decreased with increases in the FE-DBD plasma treatment time in both the non-PMA-treated and PMA + Sarkosyl-treated samples; in the non-PMA and PMA + Sarkosyl treated Jogaejeotgal, HuNoV GII.4 titers (log₁₀ copy number/µL) were to: 3.16 and 2.95 (5 min), 2.90 and 2.48 (10 min), 2.82 and 2.40 (15 min), 2.58 and 2.26 (20 min), 2.48 and 2.06 (25 min), and 2.23 and 1.91 (30 min), respectively. The average titers of HuNoV demonstrated significant (P < 0.05) reductions of 0.35 log₁₀ (55.3%) in PMA + Sarkosyl-treated samples compared with the non-PMA treated samples following exposure to 5-30 min of FE-DBD plasma. Reductions of >1-log for HuNoV in PMA + Sarkosyl- treated Jogaejeotgal required treatments of FE-DBD of 5-30 min. Using the first order kinetic model (R² = 0.95), GII.4 decimal reduction time (D-value) resulting from FE-DBD plasma was 23.75 min. The pH and Hunter colors ("L", "a", and "b") were not significantly different (P > 0.05) between the untreated and FE-DBD plasma-treated Jogaejeotgal. Based on these results, the PMA + Sarkosyl/RT-qPCR method could be assessing HuNoV viability following 5-30 min treatment of FE-DBD plasma. Furthermore, may be an optimal treatment for Jogaejeotgal without altering the food quality (color and pH).

Characterization of a GH3 halophilic β-glucosidase from Pseudoalteromonas and its NaCl-induced activity toward isoflavones

A novel β-glucosidase gene was isolated from Pseudoalteromonas sp. GXQ-1 and heterologously expressed in Escherichia coli. The activity of the encoded enzyme, PABGL, toward p-nitrophenyl-β-D-glucopyranoside was increased 8.74-fold by the presence of 3 M NaCl relative to the absence of added NaCl. PABGL hydrolyzed a variety of soy isoflavone substrates. For the conversion of daidzin to daidzein, the production rate was 1.44 mM/h. The addition of NaCl enhanced the hydrolytic activity of PABGL toward daidzin and genistein; the maximum activation by NaCl was 3.48- and 6.79-fold, respectively. This is the first report of a halophilic β-glucosidase from Pseudoalteromonas spp., and represents the β-glucosidase with the highest multiple of activation by NaCl. PABGL exhibits strong potential for applications in food processing and industrial production.

High-throughput sequence analysis of bacterial communities and their predictive functionalities in traditionally preserved fish products of Sikkim, India

Traditionally preserved fish products viz. suka ko maccha, a smoked fish product, sidra and sukuti, sun-dried fish products are commonly consumed in Sikkim state in India. Bacterial communities in these fish products were analysed by high-throughput sequence (HTS) method supported by bioinformatics tool. Metataxonomic of the overall bacterial communities in samples revealed the abundance of phylum Firmicutes followed by Proteobacteria. Psychrobacter was abundant genus in all traditionally preserved fish products of Sikkim, followed by Bacillus, Staphylococcus, Serratia, Clostridium, Enterobacter, Pseudomonas, Rummeliibacillus, Enterococcus, Photobacterium, Myroides, Peptostreptococcus, Plesiomonas and Achromobacter. Product-wise distribution showed that Bacillus was abundant in suka ko maacha and sidra samples, whereas Psychrobacter was abundant in sukuti samples. Unique genus to each product was observed on the basis of analysis of shared operational-taxonomic-unit (OTU) contents, Alpha diversity indices showed significantly differences among the samples, and also showed maximum coverage as per Good's coverage (0.99). Beta diversity showed clustering of bacterial compositions between suka ko maacha and sidra, whereas sukuti showed scattering pattern among the other samples, indicating a diverse population in suka ko maacha and sidra samples. Non-parametric analysis of abundant genera and predictive functionalities showed the complex bacterial inter-dependencies with predictive functionalities mostly in metabolism (79.88%).

Recombinant Penicillium oxalicum 16 β-Glucosidase 1 Displays Comprehensive Inhibitory Resistance to Several Lignocellulose Pretreatment Products, Ethanol, and Salt

β-Glucosidase (BGL) is a rate-limiting enzyme of lignocellulose hydrolysis for second-generation bioethanol production, but its inhibition by lignocellulose pretreatment products, ethanol, and salt is apparent. Here, the recombinant Penicillium oxalicum 16 BGL 1 (rPO16BGL1) from Pichia pastoris GS115 kept complete activity at 0.2-1.4 mg/mL furan derivatives and phenolic compounds, 50 mg/mL sodium chloride (potassium chloride), or 100 mg/mL ethanol at 40 °C. rPO16BGL1 retained above 50% residual activity at 30 mg/mL organic acid sodium, and 60% residual activity at 40 °C with 300 mg/mL ethanol. Sodium chloride and potassium chloride had a complicated effect on rPO16BGL1, which resulted in activation or inhibition. The inhibition kinetics of the enzyme reaction demonstrated that organic acids and organic acid sodium were non-competitive inhibitors and that ethanol was a competitive inhibitor at < 1.5 mg/mL salicin. Moreover, substrate inhibition of the enzyme was found at > 2 mg/mL salicin, and the Km/KI and Km/KSI average values revealed that the inhibitory strength was ranked as salicin-organic acids > organic acids > salicin-organic acid sodium salt > organic acid sodium salt > salicin > salicin-KCl > salicin-NaCl > salicin-ethanol > ethanol.

Technological roles of microorganisms in fish fermentation: a review

Fermentation is an important way to process and preserve fish. It not only gives the product a unique flavor and texture, but it also contributes to increased nutritional value and better functional properties. The production of fermented fish relies on naturally occurring enzymes (in the muscle or the intestinal tract) as well as microbial metabolic activity. This review focuses on the role of microorganisms on texture change, flavor formation, and biogenic amines accumulation in fermented fish. In addition, the production conditions and the major biochemical changes in fermented fish products are also introduced to help understand the factors influencing the quality of fermented fish. Moreover, prospects for further research of fermented fish are discussed.

Identification and functional characterization of a β-glucosidase from Bacillus tequelensis BD69 expressed in bacterial and yeast heterologous systems

Background

The identification and characterization of novel β-glucosidase genes has attracted considerable attention because of their valuable use in a variety of industrial applications, ranging from biofuel production to improved digestibility of animal feed. We previously isolated a fiber-degrading strain of Bacillus tequelensis from buffalo dung samples, and the goal of the current work was to identify β-glucosidase genes in this strain. We describe the cloning and expression of a new β-glucosidase gene (Bteqβgluc) from Bacillus tequelensis strain BD69 in bacterial and yeast hosts. The recombinant Bteqβgluc were used to characterize specificity and activity parameters, and candidate active residues involved in hydrolysis of different substrates were identified through molecular docking.

Methods

The full length Bteqβgluc gene was cloned and expressed in Escherichia coli and Pichia pastoris cultures. Recombinant Bteqβgluc proteins were purified by immobilized metal affinity or anion exchange chromatography and used in β-glucosidase activity assays measuring hydrolysis of ρ-nitrophenyl-β-D-glucopyranoside (pNPG). Activity parameters were determined by testing relative β-glucosidase activity after incubation under different temperature and pH conditions. Candidate active residues in Bteqβgluc were identified using molecular operating environment (MOE) software.

Results

The cloned Bteqβgluc gene belongs to glycoside hydrolase (GH) family 4 and encoded a 54.35 kDa protein. Specific activity of the recombinant β-glucosidase was higher when expressed in P. pastoris (1,462.25 U/mg) than in E. coli (1,445.09 U/mg) hosts using same amount of enzyme. Optimum activity was detected at pH 5 and 50 °C. The activation energy (E _a) was 44.18 and 45.29 kJ/mol for Bteqβgluc produced by P. pastoris and E. coli, respectively. Results from other kinetic parameter determinations, including pK _a for the ionizable groups in the active site, Gibbs free energy of activation (ΔG ^‡), entropy of activation (ΔS ^‡), Michaelis constant (K _m) and maximum reaction velocity (V _max) for pNPG hydrolysis support unique kinetics and functional characteristics that may be of interest for industrial applications. Molecular docking analysis identified Glu, Asn, Phe, Tyr, Thr and Gln residues as important in protein-ligand catalytic interactions.

Identification and molecular characterization of a psychrophilic GH1 β-glucosidase from the subtropical soil microorganism Exiguobacterium sp. GXG2

The products of bacterial β-glucosidases with favorable cold-adapted properties have industrial applications. A psychrophilic β-glucosidase gene named bglG from subtropical soil microorganism Exiguobacterium sp. GXG2 was isolated and characterized by function-based screening strategy. Results of multiple alignments showed that the derived protein BglG shared 45.7% identities with reviewed β-glucosidases in the UniProtKB/Swiss-Prot database. Functional characterization of the β-glucosidase BglG indicated that BglG was a 468 aa protein with a molecular weight of 53.2 kDa. The BglG showed the highest activity in pH 7.0 at 35 °C and exhibited consistently high levels of activity within low temperatures ranging from 5 to 35 °C. The BglG appeared to be a psychrophilic enzyme. The values of K_m, V_max, k_cat, and k_cat/K_m of recombinant BglG toward ρNPG were 1.1 mM, 1.4 µg/mL/min, 12.7 s⁻¹, and 11.5 mM/s, respectively. The specific enzyme activity of BglG was 12.14 U/mg. The metal ion of Ca²⁺ and Fe³⁺ could stimulate the activity of BglG, whereas Mn²⁺ inhibited the activity. The cold-adapted β-glucosidase BglG displayed remarkable biochemical properties, making it a potential candidate for future industrial applications.

Cloning and Molecular Characterization of an Alpha-Glucosidase (MalH) from the Halophilic Archaeon Haloquadratum walsbyi

We report the heterologous expression and molecular characterization of the first extremely halophilic alpha-glucosidase (EC 3.2.1.20) from the archaeon Haloquadratum walsbyi. A 2349 bp region (Hqrw_2071) from the Hqr. walsbyi C23 annotated genome was PCR-amplified and the resulting amplicon ligated into plasmid pET28b(+), expressed in E. coli Rosetta cells, and the resulting protein purified by Ni-NTA affinity chromatography. The recombinant protein showed an estimated molecular mass of 87 kDa, consistent with the expected value of the annotated protein, and an optimal activity for the hydrolysis of α-PNPG was detected at 40 °C, and at pH 6.0. Enzyme activity values were the highest in the presence of 3 M NaCl or 3-4 M KCl. However, specific activity values were two-fold higher in the presence of 3-4 M KCl when compared to NaCl suggesting a cytoplasmic localization. Phylogenetic analyses, with respect to other alpha-glucosidases from members of the class Halobacteria, showed that the Hqr. walsbyi MalH was most similar (up to 41%) to alpha-glucosidases and alpha-xylosidases of Halorubrum. Moreover, computational analyses for the detection of functional domains, active and catalytic sites, as well as 3D structural predictions revealed a close relationship with an E. coli YicI-like alpha-xylosidase of the GH31 family. However, the purified enzyme did not show alpha-xylosidase activity. This narrower substrate range indicates a discrepancy with annotations from different databases and the possibility of specific substrate adaptations of halophilic glucosidases due to high salinity. To our knowledge, this is the first report on the characterization of an alpha-glucosidase from the halophilic Archaea, which could serve as a new model to gain insights into carbon metabolism in this understudied microbial group.

Bioprospecting of novel thermostable β-glucosidase from Bacillus subtilis RA10 and its application in biomass hydrolysis

BACKGROUND

Saccharification is the most crucial and cost-intensive process in second generation biofuel production. The deficiency of β-glucosidase in commercial enzyme leads to incomplete biomass hydrolysis. The decomposition of biomass at high temperature environments leads us to isolate thermotolerant microbes with β-glucosidase production potential.

RESULTS

A total of 11 isolates were obtained from compost and cow dung samples that were able to grow at 50 °C. On the basis of qualitative and quantitative estimation of β-glucosidase enzyme production, Bacillus subtilis RA10 was selected for further studies. The medium components and growth conditions were optimized and β-glucosidase enzyme production was enhanced up to 19.8-fold. The β-glucosidase from B. subtilis RA10 retained 78% of activity at 80 °C temperature and 68.32% of enzyme activity was stable even at 50 °C after 48 h of incubation. The supplementation of β-glucosidase from B. subtilis RA10 into commercial cellulase enzyme resulted in 1.34-fold higher glucose release. Furthermore, β-glucosidase was also functionally elucidated by cloning and overexpression of full length GH1 family β-glucosidase gene from B. subtilis RA10. The purified protein was characterized as thermostable β-glucosidase enzyme.

CONCLUSIONS

The thermostable β-glucosidase enzyme from B. subtilis RA10 would facilitate efficient saccharification of cellulosic biomass into fermentable sugar. Consequently, after saccharification, thermostable β-glucosidase enzyme would be recovered and reused to reduce the cost of overall bioethanol production process.

Oral administration of lactobacilli isolated from Jeotgal, a salted fermented seafood, inhibits the development of 2,4-dinitrofluorobenzene-induced atopic dermatitis in mice

Certain strains of lactobacilli have been reported to exert favorable effects on atopic dermatitis (AD). Jeotgal, a traditional Korean food, is a salted fermented seafood known to harbor many lactic acid bacteria. In the present study, two novel lactobacillus strains were isolated from Jeotgal, and their anti-AD effects were investigated. Lactobacilli isolated from Jeotgal were identified, according to conjugated linoleic acid-producing activity, as Lactobacillus plantarum (JBCC105645 and JBCC105683). AD-like skin lesions were induced in BALB/c mice using dinitrofluorobenzene (DNFB). Ear swelling, histological analysis and serum immunoglobulin E (IgE) levels in mice were evaluated to investigate the anti-AD effects of lactobacilli. Cytokine production of ex vivo cluster of differentiation (CD)4⁺ T cells, and interleukin (IL)-12 production of in vitro macrophages were also evaluated to establish a putative mechanism of the action of lactobacilli. Administration of JBCC105645 or JBCC105683 suppressed ear swelling and serum IgE levels in DNFB-treated mice (P<0.05). Notably, JBCC105645 was more effective than JBCC105683 (P<0.05). Treatment with the lactobacilli also induced a significant decrease in IL-4 production with concomitant increase in interferon (IFN)-γ production in DNFB-exposed CD4⁺ T cells, and an increase in IL-12 production in macrophages (P<0.05). Taken together, the lactobacilli isolated from Jeotgal may suppress the development of AD-like skin inflammation in mice by modulating IL-4 and IFN-γ production in CD4⁺ T cells, presumably via enhancing IL-12 production by macrophages.