Hydrolysis of soybean isoflavone glycosides by a thermostable β-glucosidase from Paecilomyces thermophila

Characterization of β-glucosidase activity of a Lactiplantibacillus plantarum 6-phospho-β-glucosidase

β-Glucosidases are useful for hydrolysis of glycosidically-bound volatiles (GBV), thereby facilitating the release of aroma chemicals from the fruit matrices. In this study, 10 putative glycosyl hydrolases belonging to GH1 family from Lactiplantibacillus plantarum NCIM 2903 were cloned and recombinantly expressed. Interestingly, only one (LpBgl5) of the nine soluble proteins, previously characterized as a 6-phospho-β-glucosidase showed β-glucosidase activity which was further characterized. The enzyme had an optimum pH and temperature of 6 and 40°C, respectively, and was categorized as aryl-β-glucosidase due to its ability to hydrolyze different natural as well as synthetic glucosides except cellobiose. The enzyme exhibited functional activity across multiple substrates, with relative activity decreasing sequentially from β-xylosidase to β-glucosidase and finally β-mannosidase. The β-xylosidase and β-glucosidase activities of LpBgl5 were stimulated up to 300% and 700% in the presence of 4 M xylose and 4 M glucose, respectively. The enzyme could also hydrolyze GBV from mango. To our knowledge, this is the first recombinant β-glucosidase/β-xylosidase/β-mannosidase from L. plantarum to have potential for aroma enhancement in fruit products. KEY POINTS: • A recombinant β-glycosidase from Lactiplantibacillus plantarum was characterized. • The enzyme showed higher β-xylosidase activity than β-glucosidase activity. • The enzyme could also hydrolyze glycosidically bound volatiles from mango.

New insights of flavonoid glycosidases and their application in food industry

Flavonoids are significant natural nutraceuticals and a key component of dietary supplements. Given that flavonoid glycosides are more plentiful in nature and less beneficial to human health than their aglycone counterparts, they serve as potential precursors for flavonoid production. Glycosidases have shown substantial potential within the food industry, particularly in enhancing the organoleptic properties of juice, wine, and tea. When applied to food resources, glycosidases can amplify their biological activities, thereby improving the performance of functional foods. This review provides up-to-date information on flavonoid glycosidases, including their catalytic mechanisms, biochemical properties, and natural sources, as well as their applications within the food industry. The use of flavonoid glycosidases in improving food quality is also reviewed.

A review on applications of β-glucosidase in food, brewery, pharmaceutical and cosmetic industries

β-glucosidases hydrolyse glycosidic bonds to release non-reducing terminal glucosyl residues from glycosides and oligosaccharides via catalytic mechanisms. It is very well known that the β-glucosidase enzyme is used in biorefineries for cellulose degradation, where β-glucosidases is the rate-limiting enzyme for the final glucose production from cellobiose. The β-glucosidase enzyme is used as a catalyst in other industrial sectors, including pharmaceuticals, breweries, dairy, and food processing. With the aid of β-glucosidase enzymes, cyanogenic glycosides and plant glycosides are transformed into sugar moiety and aglycones. These aglycone compounds are employed as aromatic compounds in the food processing and brewing industries. They are also used as medications and dietary supplements based on their pharmacological qualities. Applications of aglycones and the microbiological sources of β-glucosidase in aglycone production have been discussed in this review.

A study on the catalytic activity of polypeptides toward the hydrolysis of glucoside compounds gastrodin, polydatin and esculin

The self-assembly of a series of catalytically active polypeptides toward hydrolysis of glucoside compounds, namely, gastrodin, polydatin and esculin was investigated. These active peptides are composed of two functional fragments: one is the hydrophobic sequence LHLHLRL, which forms assembling segments in the presence of Zn ions (Zn²⁺); another functional sequence of active peptides are catalytic sites such as Glu (E), Asp (D) and His (H), where carboxylic acids (-COOH) or imidazole groups act like scissors to cleave glucoside bonds of the compounds (according to the acid-base coupling mechanism). The effects of the amino acid sequence of the peptide, Zn²⁺ concentration, pH and the size or steric hindrance of glucoside compounds on the hydrolytic activity were studied. It was found that the crystalline structure of assembled peptides was crucial to provide the peptide with catalytic hydrolytic activity. Noncovalent interaction index was used to analyse the noncovalent interaction of PEs with glucoside compounds, including hydrogen bonds, van der Waals, and steric effect in the complexes. The binding energy of complexes, the direction and site of nucleophilic attack during deglycosylation processes were also investigated by molecular docking and the electron density Laplace function. This revealed that the differences in the hydrolytic activity of peptides toward glucoside compounds with different sizes originated from different hydrogen bond interactions between the peptides and substrates. These active peptides may find application in the preparation of drugs by de-glycosylation of natural compounds.

Effect of pulsed electric field on soybean isoflavone glycosides hydrolysis by β-glucosidase: Investigation on enzyme characteristics and assisted reaction

This work aimed to investigate how pulsed electric field (PEF) technology as an alternative to enhance the enzymatic hydrolysis of soybean isoflavone glycosides (SIG). To achieve it, the effect of PEF treatment on the activity, kinetics, thermodynamics and structure of β-glucosidase (β-GLU) were evaluated. The parameters for PEF-assisted hydrolysis of soybean isoflavone glycosides were optimized by response surface methodology. The results showed that PEF treatment increased the relative activity and catalytic efficiency of β-GLU with moderate electric field intensity. Furthermore, PEF treatment induced the secondary and tertiary structural change of β-GLU, the α-helix content increased by 4.23% and the β-fold content decreased by 3.70%. The optimum conditions for PEF treatment were established as the highest yield of isoflavone aglycones achieved 94.58%. Therefore, these results indicated that PEF treatment could be used as an efficient process to improve the β-GLU properties, converting soybean isoflavone glycoside to their aglycones form.

Production of Daidzein and Genistein from Seed and Root Extracts of Korean Wild Soybean (Glycine soja) by Thermostable β-Galactosidase from Thermoproteus uzoniensis

Isoflavone glycosides are commonly biotransformed into isoflavone aglycones due to the superior biological activities of the latter. Wild soybeans contain a higher isoflavone content than domesticated soybeans due to their high level of genetic diversity. In this study, we cloned and characterized a thermostable β-galactosidase from the extreme thermophile Thermoproteus uzoniensis for potential application in isoflavone conversion in Korean wild soybeans. The purified recombinant enzyme exhibited a maximum specific activity of 1103 μmol/min/mg at pH 5.0 and 90 °C with a half-life of 46 h and exists as a homodimer of 113 kDa. The enzyme exhibited the highest activity for p-nitrophenyl (pNP)-β-D-galactopyranoside among aryl glycosides and it hydrolyzed isoflavone glycosides in the order genistin > daidzin > ononin > glycitin. The enzyme completely hydrolyzed 2.77 mM daidzin and 3.85 mM genistin in the seed extract of wild soybean after 80 and 70 min with productivities of 1.86 and 3.30 mM/h, respectively, and 9.89 mM daidzin and 1.67 mM genistin in the root extract after 180 and 30 min, with the highest productivities of 3.30 and 3.36 mM/h, respectively, compared to other glycosidases. Our results will contribute to the industrial production of isoflavone aglycone using wild soybean and this is the first report on the enzymatic production of isoflavone aglycones from isoflavone glycosides in wild soybeans.

Characterization of a novel isoflavone glycoside-hydrolyzing β-glucosidase from mangrove soil metagenomic library

For the beneficial pharmacological properties of isoflavonoids and their related glycoconjugates, there is increasingly interest in their enzymatic conversion. In this study, a novel β-glucosidase gene isolated from metagenomic library of mangrove sediment was cloned and overexpressed in Escherichia coli BL21(DE3). The purified recombination β-glucosidase, designated as r-Bgl66, showed high catalytic activity for soy isoflavone glycosides. It converted soy isoflavone flour extract with the productivities of 0.87 mM/h for daidzein, 0.59 mM/h for genistein and 0.42 mM/h for glycitein. The kcat/Km values for daidzin, genistin and glycitin were 208.73, 222.37 and 288.07 mM-1 s-1, respectively. In addition, r-Bgl66 also exhibited the characteristic of glucose-tolerance, and the inhibition constant Ki was 471.4 mM. These properties make it a good candidate in the enzymatic hydrolysis of soy isoflavone glycosides. This study also highlights the utility of metagenomic approach in discovering novel β-glucosidase for soy isoflavone glycosides hydrolysis.

Antioxidant Effect of Soymilk Fermented by Lactobacillus plantarum HFY01 on D-Galactose-Induced Premature Aging Mouse Model

The antioxidant effect of soymilk fermented by Lactobacillus plantarum HFY01 (screened from yak yogurt) was investigated on mice with premature aging induced by D-galactose. In vitro antioxidant results showed that L. plantarum HFY01-fermented soymilk (LP-HFY01-DR) had better ability to scavenge the free radicals 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) diammonium salt (ABTS) than unfermented soymilk and Lactobacillus bulgaricus-fermented soymilk. Histopathological observation showed that LP-HFY01-DR could protect the skin, spleen and liver, reduce oxidative damage and inflammation. Biochemical results showed that LP-HFY01-DR could effectively upregulate glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) levels and decrease malondialdehyde (MDA) content in the liver, brain, and serum. Real-time quantitative reverse transcription polymerase chain reaction further showed that LP-HFY01-DR could promote the relative expression levels of the genes encoding for cuprozinc superoxide dismutase (Cu/Zn-SOD, SOD1), manganese superoxide dismutase (Mn-SOD, SOD2), CAT, GSH, and GSH-Px in the liver, spleen, and skin. High-performance liquid chromatography results revealed daidzin, glycitin, genistin, daidzein, glycitein, and genistein in LP-HFY01-DR. In conclusion, LP-HFY01-DR could improve the antioxidant capacity in mice with premature aging induced by D-galactose.

Long term crop rotation effect on subsequent soybean yield explained by soil and root-associated microbiomes and soil health indicators

Crop rotation is an important management tactic that farmers use to manage crop production and reduce pests and diseases. Long-term crop rotations may select groups of microbes that form beneficial or pathogenic associations with the following crops, which could explain observed crop yield differences with different crop sequences. To test this hypothesis, we used two locations each with four long-term (12–14-year), replicated, rotation treatments: continuous corn (CCC), corn/corn/soybean (SCC), corn/soybean (CSC), and soybean/corn (SCS). Afterwards, soybean was planted, and yield and soil health indicators, bulk soil microbiome, and soybean root-associated microbiome were assessed. Soybean yields, as well as soil protein, and POXC as soil health indicators were higher following CCC than in the other three treatments at both locations. A bacterial taxon in family JG30-KF-AS9 was enriched in CCC, whereas Microvirga, Rhodomicrobium, and Micromonosporaceae were enriched in SCS. Several ascomycetes explain lowered yield as soybean pathogens in SCS. Surprisingly, Tumularia, Pyrenochaetopsis and Schizothecium were enriched in soybean roots after CCC, suggesting corn pathogens colonizing soybean roots as nonpathogens. Our finding of associations between soil health indicators related to microbiomes and soybean yield has wide-ranging implications, opening the possibility of manipulating microbiomes to improve crop yield potential.

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.

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.

Biotransformation processes in soymilk isoflavones to enhance anti-inflammatory potential in intestinal cellular model

The present study investigated, in in vitro cellular model, the modulation of intestinal inflammation by biotransformed soymilk with tannase and probiotic strains. The ability to reduce the generation of intracellular reactive oxygen species (ROS) and the antioxidant power of soy extracts were also evaluated. The results showed changes in isoflavones profile after biotransformation processes, with a significative enhancement in aglycones content. Reduction in intracellular ROS production and improvement in antioxidant capacity were observed. Anti-inflammatory responses in Caco-2 cells were also expressive. A significative decrease in interleukin 8 (IL-8) level was detected for all biotransformed samples, especially for extracts with tannase. The biotransformed soy extracts by tannase have a great potential to improve health conditions, defending the intestinal cells of oxidative damage, and acting as a possible adjuvant in inflammatory process. PRACTICAL APPLICATIONS: Soy isoflavones have been explored owing to health benefits. Only glycosylated forms are found in high concentrations in soybeans. So, microbial and enzymatic biotransformation processes aiming to increase aglycones and metabolites appear as an attractive option to enlarge the bioactivity of soy products. The present study showed a positive impact of biotransformed soymilk on antioxidant defenses systems and modulation of intestinal inflammation and could act as a nutraceutical agent.

Deglycosylation patterns of isoflavones in soybean extracts inoculated with two enzymatically different strains of lactobacillus species

Microorganism selection is critical to deglycosylation in soybean fermentation for producing beneficial phytochemicals. This study investigated isoflavone bioconversion in soybean extract inoculated with Lactobacillus plantarum K2-12 and Lactobacillus curvatus JD0-31 exhibiting different enzyme activities. L. plantarum showed higher esterase (C4), esterase (C8), β-galactosidase, α-glucosidase, β-glucosidase, and N-acetyl-β-glucosaminase activities. We found that isoflavone bioconversion was distinguished into isoflavone backbone structure types. Malonyl- and acetyl- types of isoflavones except for malonyl daidzin were not significantly differed their contents between lactobacilli. Deglycosylating severity was observed in malonyl genistin in both lactobacilli, resulting mass production of genistein. On the other hand, daidzein glycosides were dependable to lactobacilli, in which L. plantarum efficiently degraded malonyl daidzin and daidzin in fast time. Glycitein was most degradable among the three aglycones by fermentation. These results suggest that efficient control of isoflavone deglycosylation by Lactobacillus species should be controlled to the inoculation period and select target isoflavones.

Green construction of recyclable amino-tannic acid modified magnetic nanoparticles: Application for β-glucosidase immobilization

The β-glucosidase (BGL) enzyme in food industry is great interest due to its role in food conversion to produce functional food products. In this study, the BGL was covalently immobilized onto amino-tannic acid modified Fe₃O₄ magnetic nanoparticles (ATA-Fe₃O₄ MNPs) as biocompatible nanoplatform by modified poly-aldehyde pullulan (PAP) as a cross-linker to enhance the ability and strength of the nanoparticle connection to the enzyme. The properties of support were subsequently characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The highest percentage of loading and immobilization yield was obtained with 0.1 mg enzyme/mL citrate buffer (pH 6, 1 M) enzyme solution, carrier solution of 10 mg ATA-Fe₃O₄/3 mL citrate buffer (pH 6, 1 M), and PAP solution of 20% total reaction system volume. Optimum pH and temperature were found for free (pH 5.0 and temperature 30 °C) and immobilized (pH 6.0 and temperature 40 °C) enzyme. The immobilized BGL maintains its activity to 83% after 10 cycles. Therefore, immobilization of BGL by this method is an efficient procedure to improve the properties of enzyme.

Isolation of Penicillium citrinum from Roots of Clerodendron cyrtophyllum and Application in Biosynthesis of Aglycone Isoflavones from Soybean Waste Fermentation

Soybeans offer an abundant source of isoflavones, which confer useful bioactivities when existing in aglycone forms. The conversion of isoflavones into aglycones via fermentation of soybean products is often realized by β-glucosidase, an enzyme produced by fungi. In this study, a filamentous fungus, Clerodendron cyrtophyllum, was isolated from root of Clerodendron cyrtophyllum Turcz, which was able to produce the highest activity of β-glucosidase up to 33.72 U/mL at 144 h during fermentation on Potato Dextrose Broth (PDB). The obtained fungus was grown on isoflavones-rich soybean extract to produce genistein and daidzein, achieving the conversion rate of 98.7%. Genistein and daidzein were isolated and purified by column chromatography using hexane/acetone (29:1/1:1), reaching purities of over 90% of total isoflavones, as identified and determined by TLC, LC-MS/MS, and 1H and 13C NMR spectroscopy. These results imply that the isolated P. citrinum is a potential fungal strain for industrial-scale production of genistein and daidzein from isoflavones-containing soybean extracts. These products may serve as potential raw materials for manufacture of functional foods that are based on aglycones.

Simultaneous Characterization and Quantification of Varied Ingredients from Sojae semen praeparatum in Fermentation Using UFLC⁻TripleTOF MS

Systematic comparison of active ingredients in Sojae semen praeparatum (SSP) during fermentation was performed using ultra-fast liquid chromatography (UFLC)-TripleTOF MS and principal component analysis (PCA). By using this strategy, a total of 25 varied compounds from various biosynthetic groups were assigned and relatively quantified in the positive or negative ion mode, including two oligosaccharides, twelve isoflavones, eight fatty acids, N-(3-Indolylacetyl)-dl-aspartic acid, methylarginine, and sorbitol. Additionally, as the representative constituents, six targeted isoflavones were sought in a targeted manner and accurately quantified using extracted ion chromatograms (XIC) manager (AB SCIEX, Los Angeles, CA, USA) combined with MultiQuant software (AB SCIEX, Los Angeles, CA, USA). During the fermentation process, the relative contents of oligoses decreased gradually, while the fatty acids increased. Furthermore, the accurate contents of isoflavone glycosides decreased, while aglycones increased and reached a maximum in eight days, which indicated that the ingredients converted obviously and regularly throughout the SSP fermentation. In combination with the morphological changes, which meet the requirements of China Pharmacopoeia, this work suggested that eight days is the optimal time for fermentation of SSP from the aspects of morphology and content.

Biotransformation of soy flour isoflavones by Aspergillus niger NRRL 3122 β-glucosidase enzyme

β-glucosidase enzyme produced from Aspergillus niger NRRL 3122 has been partially purified and characterised. Its molecular weight was 180 KDa. The optimal pH and temperature were 3.98 and 55 °C, respectively. It promoted the hydrolysis of soy flour isoflavone glycosides to their aglycone. Two-level Plackett-Burman design was applied and effective variables for genistein production were determined. Reaction time had a significant positive effect, and pH had a significant negative effect. They were further evaluated using Box-Behnken model. Accordingly, the optimal combination of the major reaction affecting factors was reaction time, 5 h and pH, 4. The concentration of genistein increased by 11.73 folds using this optimal combination. The antioxidant activity of the non-biotransformed and biotransformed soy flour extracts was determined by DPPH method. It was found that biotransformation increased the antioxidant activity by four folds.

Molecular cloning, characterization and in silico analysis of a thermostable β-glucosidase enzyme from Putranjiva roxburghii with a significant activity for cellobiose

The native Putranjiva roxburghii family 1 glycoside hydrolase enzyme showed β-D-fucosidase activity in addition to β-D-glucosidase and β-D-galactosidase activities reported in our previous study. A single step concanvalin A affinity chromatography for native PRGH1 improved the yield and reduced the purification time. The PRGH1 gene was cloned and overexpressed in E. coli. The full length gene contained an ORF of 1617 bp encoding a polypeptide of 538 amino acids. The amino acid sequence of PRGH1 showed maximum similarities to β-glucosidases and myrosinases. Both native and recombinant protein showed maximum hydrolytic activity for pNP-Fuc followed by pNP-Glc and pNP-Gal. Significant enzyme activity was also observed for cellobiose, however it decreased with increase in chain-length for glycan substrates. The enzyme showed significant resistant to D-glucose concentration up to 500 mM. Mutational studies confirmed the predicted catalytic acid/base Glu173 and nucleophile Glu389 as key residues for its activity. Moreover, Glu446 and Asn172 played essential role in substrate binding by interacting with the -1 subsite of substrates. Bioinformatic analysis suggested the possible reasons for the broad substrate specificity and other properties of the enzyme. PRGH1 had high sequence similarity towards S-glucosidase and may be involved in defence. The broad specificity, catalytic efficiency and thermostability make PRGH1 potentially an important industrial enzyme.

Survival of Microencapsulated Probiotic Bacteria after Processing and during Storage: A Review

The use of live probiotic bacteria as food supplement has become popular. Capability of probiotic bacteria to be kept at room temperature becomes necessary for customer's convenience and manufacturer's cost reduction. Hence, production of dried form of probiotic bacteria is important. Two common drying methods commonly used for microencapsulation are freeze drying and spray drying. In spite of their benefits, both methods have adverse effects on cell membrane integrity and protein structures resulting in decrease in bacterial viability. Microencapsulation of probiotic bacteria has been a promising technology to ensure bacterial stability during the drying process and to preserve their viability during storage without significantly losing their functional properties such acid tolerance, bile tolerance, surface hydrophobicity, and enzyme activities. Storage at room temperatures instead of freezing or low temperature storage is preferable for minimizing costs of handling, transportation, and storage. Concepts of water activity and glass transition become important in terms of determination of bacterial survival during the storage. The effectiveness of microencapsulation is also affected by microcapsule materials. Carbohydrate- and protein-based microencapsulants and their combination are discussed in terms of their protecting effect on probiotic bacteria during dehydration, during exposure to harsh gastrointestinal transit and small intestine transit and during storage.

Highly Efficient Enzymatic Preparation of Daidzein in Deep Eutectic Solvents

Daidzein, which is scarce in nature, has gained significant attention due to its superior biological activity and bioavailability compared with daidzin. So far, it has been widely used in the medicine and health care products industries. The enzymatic approach for the preparation of daidzein has prevailed, benefitted by its high efficiency and eco-friendly nature. Our present research aimed at providing a preparation method of daidzein by enzymatic hydrolysis of daidzin in a new "green" reaction medium-deep eutectic solvents (DESs). Herein, the DESs were screened via evaluating enzyme activity, enzyme stability and the substrate solubility, and the DES (ChCl/EG 2:1, 30 vol %) was believed to be the most appropriate co-solvent to improve the bioconversion efficiency. Based on the yield of daidzein, response surface methodology (RSM) was employed to model and optimize the reaction parameters. Under these optimum process conditions, the maximum yield of 97.53% was achieved and the purity of daidzein crude product reached more than 70%, which is more efficient than conversions in DESs-free buffer. Importantly, it has been shown that DESs medium could be reused for six batches of the process with a final conversion of above 50%. The results indicated that this procedure could be considered a mild, environmentally friendly, highly efficient approach to the economical production of daidzein, with a simple operation process and without any harmful reagents being involved.

Functional beverage from fermented soymilk with improved amino nitrogen, β-glucosidase activity and aglycone content using Bacillus subtilis starter

The bioactivity of soymilk was enhanced by fermentation with three strains of β-glucosidaseproducing Bacillus subtilis for 36 h at 37oC. The results indicated that protease, cellulase, and β-glucosidase activities were significantly (p<0.05) increased with increasing fermentation time. In addition, the amino-type nitrogen content in B. subtilis-fermented soymilk was increased to 121.1-140.7 mg% after 36 h of fermentation. Among the isoflavones in soymilk, the contents of β-glucosides or acetyl-glucosides were decreased, while aglycone content was increased by fermentation. In particular, the soymilk fermented with B. subtilis HJ18-9 had highest β-glucosidase activity and the largest increase in aglycone content. The total aerobic and anaerobic cell counts were increased with increasing fermentation time. Therefore, this study suggests that soy beverages fermented with β-glucosidase-producing B. subtilis have the potential to enhance the health and nutritional status of consumers.

Characterization of β-glucosidase from Aspergillus terreus and its application in the hydrolysis of soybean isoflavones

An extracellular β-glucosidase produced by Aspergillus terreus was identified, purified, characterized and was tested for the hydrolysis of soybean isoflavone. Matrix-assisted laser desorption/ionization with tandem time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF MS) revealed the protein to be a member of the glycosyl hydrolase family 3 with an apparent molecular mass of about 120 kDa. The purified β-glucosidase showed optimal activity at pH 5.0 and 65 °C and was very stable at 50 °C. Moreover, the enzyme exhibited good stability over pH 3.0-8.0 and possessed high tolerance towards pepsin and trypsin. The kinetic parameters Km (apparent Michaelis-Menten constant) and Vmax (maximal reaction velocity) for p-nitrophenyl-β-D-glucopyranoside (pNPG) were 1.73 mmol/L and 42.37 U/mg, respectively. The Km and Vmax for cellobiose were 4.11 mmol/L and 5.7 U/mg, respectively. The enzyme efficiently converted isoflavone glycosides to aglycones, with a hydrolysis rate of 95.8% for daidzin, 86.7% for genistin, and 72.1% for glycitin. Meanwhile, the productivities were 1.14 mmol/(L·h) for daidzein, 0.72 mmol/(L·h) for genistein, and 0.19 mmol/(L·h) for glycitein. This is the first report on the application of A. terreus β-glucosidase for converting isoflavone glycosides to their aglycones in soybean products.

Heterologous expression of a GH3 β-glucosidase from Neurospora crassa in Pichia pastoris with high purity and its application in the hydrolysis of soybean isoflavone glycosides

Previous studies have shown isoflavone aglycones to have more biological effects than their counterparts, isoflavone glycones. Some β-glucosidases can hydrolyze isoflavone glucosides to release aglycones, and discovery of these has attracted great interest. A glycoside hydrolase (GH) family 3 β-glucosidase (bgl2) gene from Neurospora crassa was heterologously expressed in Pichia pastoris with high purity. The recombinant BGL2 enzyme displayed its highest activity at pH 5.0 and 60 °C, and had its maximum activity against p-nitrophenyl-β-d-glucopyranoside (pNPG) (143.27 ± 4.79 U/mg), followed by cellobiose (74.99 ± 0.78 U/mg), gentiobiose (47.55 ± 0.15 U/mg), p-nitrophenyl-β-d-cellobioside (pNPC) (40.07 ± 0.87 U/mg), cellotriose (12.31 ± 0.36 U/mg) and cellotetraose (9.04 ± 0.14 U/mg). The kinetic parameters of Km and Vmax were 0.21 ± 0.01 mM and 147.93 ± 2.77 μM/mg/min for pNPG. The purified enzyme showed a heightened ability to convert the major soybean isoflavone glycosides (daidzin, genistin and glycitin) into their corresponding aglycone forms (daidzien, genistein and glycitein). With this activity against soybean isoflavone glycosides, BGL2 shows great potential for applications in the food, animal feed, and pharmaceutical industries.

High production of succinyl isoflavone glycosides by Bacillus licheniformis ZSP01 resting cells in aqueous miscible organic medium

To achieve efficient production of succinyldaidzin and succinylgenistin, resting cells of a solvent-stable strain Bacillus licheniformis ZSP01 were used to react with pure isoflavones or soybean flour extract in a reaction medium with 10% dimethyl sulfoxide. Strikingly, 0.8 mM daidzein, 0.8 mM genistein, 2.0 mM daidzin, and 2.0 mM genistin were transformed to succinyl isoflavone glycosides in 27 H (yield >90%). The soybean flour extract (6.1%, w/v) contained 0.32 mM daidzein, 0.84 mM daidzin, 0.38 mM genistein, and 1.04 mM genistin. Over 95% of total isoflavones (daidzein, daidzin, genistein, and genistin) in the soybean flour extract were converted to succinyl isoflavone glycosides after 27 H. Strain ZSP01 shows both high glycosylation and succinylation activities. These results suggest that B. licheniformis ZSP01 could be useful for the efficient production of succinyl soybean isoflavone glycosides.

Characterization of a novel β-glucosidase from Gongronella sp. W5 and its application in the hydrolysis of soybean isoflavone glycosides

A novel β-glucosidase named BglW5 from Gongronella sp. was isolated, purified, and characterized for the first time. Under solid state fermentation, the yield of BglW5 was 49.9 U/g fermented medium. BglW5 was stable over a wide pH range of 3.0-8.5 and retained more than 50% of its maximal activity after incubation at 25 °C for 96 h. The half-lives of BglW5 were 20 h at 60 °C, and 1 h at 70 °C. The activity of BglW5 was stimulated by xylose and fructose at concentrations up to 500 mM, with maximal stimulatory effect of 1.6-fold and 2.2-fold, respectively. BglW5 converted isoflavone glycosides to aglycones, with a hydrolysis rate of 96.2% for daidzin and 96.7% for genistin. The productivities were 1.5 mmol L(-1) h(-1) for daidzein and 1.23 mmol L(-1) h(-1) for genistein, respectively. These features suggest that BglW5 has great application potential in the hydrolysis of soybean isoflavone glycosides.

Molecular characterization of a highly-active thermophilic β-glucosidase from Neosartorya fischeri P1 and its application in the hydrolysis of soybean isoflavone glycosides

Isoflavone occurs abundantly in leguminous seeds in the form of glycoside and aglycone. However, isoflavone glycoside has anti-nutritional effect and only the free type is beneficial to human health. In the present study we identified a β-glucosidase from thermophilic Neosartorya fischeri P1, termed NfBGL1, capable of efficiently converting isoflavone glycosides into free isoflavones. The gene, belonging to glycoside hydrolase family 3, was successfully overexpressed in Pichia pastoris at high cell density in a 3.7-l fermentor. Purified recombinant NfBGL1 had higher specific activity (2189 ± 1.7 U/mg) and temperature optimum (80 °C) than other fungal counterparts when using p-nitrophenyl β-D-glucopyranoside as the substrate. It retained stable at temperatures up to 70 °C and over a broad pH range of 3.0-10.0. NfBGL1 had broad substrate specificity including glucosidase, cellobiase, xylanase and glucanase activities, and displayed preference for hydrolysis of β-1,2 glycosidic bond rather than β-1,3, β-1,4, β-1,6 bonds. The enzyme showed high bioconversion ability for major soybean isoflavone glycosides (daidin, gensitin and glycitin) into free forms. These properties make NfBGL1 potential for the wide use in the food, feed, pharmacy and biofuel industries.

Cellulolytic and xylanolytic potential of high β-glucosidase-producing Trichoderma from decaying biomass

Availability, cost, and efficiency of microbial enzymes for lignocellulose bioconversion are central to sustainable biomass ethanol technology. Fungi enriched from decaying biomass and surface soil mixture displayed an array of strong cellulolytic and xylanolytic activities. Strains SG2 and SG4 produced a promising array of cellulolytic and xylanolytic enzymes including β-glucosidase, usually low in cultures of Trichoderma species. Nucleotide sequence analysis of internal transcribed spacer 2 (ITS2) region of rRNA gene revealed that strains SG2 and SG4 are closely related to Trichoderma inhamatum, Trichoderma piluliferum, and Trichoderma aureoviride. Trichoderma sp. SG2 crude culture supernatant correspondingly displayed as much as 9.84 ± 1.12, 48.02 ± 2.53, and 30.10 ± 1.11 units mL(-1) of cellulase, xylanase, and β-glucosidase in 30 min assay. Ten times dilution of culture supernatant of strain SG2 revealed that total activities were about 5.34, 8.45, and 2.05 orders of magnitude higher than observed in crude culture filtrate for cellulase, xylanase, and β-glucosidase, respectively, indicating that more enzymes are present to contact with substrates in biomass saccharification. In parallel experiments, Trichoderma species SG2 and SG4 produced more β-glucosidase than the industrial strain Trichoderma reesei RUT-C30. Results indicate that strains SG2 and SG4 have potential for low cost in-house production of primary lignocellulose-hydrolyzing enzymes for production of biomass saccharides and biofuel in the field.

Hydrolysis of soybean isoflavones by Debaryomyces hansenii UFV-1 immobilised cells and free β-glucosidase

An intracellular β-glucosidase from Debaryomyceshansenii UFV-1 was produced in an YP medium with cellobiose as the carbon source. This enzyme was purified, characterised and presented a Mr of 65.15kDa. Yeast cells containing the intracellular β-glucosidase were immobilised in calcium alginate. The free β-glucosidase and immobilised cells containing the enzyme presented optima values of pH and temperature of 6.0 and 45°C and 5.5 and 50°C, respectively. The free enzyme maintained 62% and 47% of its original activity after 90days at 4°C and after 15days at room temperature, respectively. The immobilisation process resulted in higher enzyme thermostability at 45 and 50°C. Soy molasses treatment with the free enzyme and the immobilised cells containing β-glucosidase, for 2h at 40°C, promoted efficient hydrolysis of isoflavone glicosides to their aglycon forms. The results suggest that this enzyme could be used in the food industry, in the free or immobilised forms, for a safe and efficient process to hydrolyse isoflavone glycosides in soy molasses.

Exploration of a cheaper carbon source for extracellular β-glucosidase synthesis from Debaryomyces pseudopolymorphus NRRL YB-4229

In the present work, interactions between common media components and fermentation conditions were explored to come up with a simple media recipe for extracellular β-glucosidase (Dβ-gl) synthesis from Debaryomyces pseudopolymorphus to substitute cellobiose, which is currently used as a sole carbon source. Taguchi L25 orthogonal array design was used to screen factors influencing Dβ-gl synthesis (carbon, organic nitrogen, inorganic nitrogen, trace elements, inoculum volume, and fermentation time). A significant influence of xylose, peptone, and potassium nitrate as carbon, organic nitrogen, and inorganic nitrogen sources, respectively, on Dβ-gl synthesis was identified by Taguchi. These factors were further optimized using central composite rotatable design (CCRD) of response surface methodology (RSM). The results showed that in the range studied, potassium nitrate had insignificant effect while xylose, peptone, and xylose-peptone interaction had a significant effect on Dβ-gl synthesis. Peptone/xylose ratio of 1.33 was found to be an important parameter for inducing Dβ-gl synthesis. The regression coefficient (R (2)) of 0.915 and P value of <0.0003 for the model indicated that it was highly significant. The maximum activity obtained after RSM (32.2 U/ml) was comparable with that obtained (68.8 U/ml) when cellobiose (20 g/l) was used as a sole carbon source. Considering the cost difference between xylose and cellobiose, a 16-fold cost reduction could be obtained for equivalent Dβ-gl yield. Fed-batch fermentations were carried out wherein peptone/xylose ratio of 1.33 was maintained and continuous Dβ-gl synthesis was observed.

Deglycosylation of isoflavones in isoflavone-rich soy germ flour by Aspergillus oryzae KACC 40247

Aspergillus oryzae KACC 40247 was selected as an efficient daidzein-producing fungus from strains of the genus Aspergillus by using 5% (w/v) soy germ flour (SGF) as an isoflavone-glycoside-rich medium. The culture conditions, including SGF concentration, agitation speed, initial pH, temperature, and time, were optimized as follows: 7% (w/v) SGF, initial pH 6.0, 33 °C, 300 rpm, and 24 h in a 100 mL baffled flask. The determined amount of isoflavone aglycons in SGF using 50% ethyl acetate was the highest among the solvent systems tested and it was 3.7-fold higher than that using 70% methanol. Under the optimized conditions, the content and concentration of daidzein were 134 mg/g of SGF and 9.4 g/L, respectively, with a productivity of 391 ± 2.8 mg/L/h, and those of isoflavone aglycons were 165 mg/g of SGF and 11.5 g/L, respectively, with a productivity of 479 mg/L/h. Optimization of culture conditions increased the content, concentration, and productivity of isoflavone aglycons by 3.1-, 3.0-, and 3.7-fold, respectively. To our knowledge, this is the highest production of isoflavone aglycons reported to date.

Role and significance of beta-glucosidases in the hydrolysis of cellulose for bioethanol production

One of the major challenges in the bioconversion of lignocellulosic biomass into liquid biofuels includes the search for a glucose tolerant beta-gulucosidase. Beta-glucosidase is the key enzyme component present in cellulase and completes the final step during cellulose hydrolysis by converting the cellobiose to glucose. This reaction is always under control as it gets inhibited by its product glucose. It is a major bottleneck in the efficient biomass conversion by cellulase. To circumvent this problem several strategies have been adopted which we have discussed in the article along with its production strategies and general properties. It plays a very significant role in bioethanol production from biomass through enzymatic route. Hence several amendments took place in the commercial preparation of cellulase for biomass hydrolysis, which contains higher and improved beta-glucosidase for efficient biomass conversion. This article presents beta-glucosidase as the key component for bioethanol from biomass through enzymatic route.

Molecular cloning and characterization of a novel β-glucosidase with high hydrolyzing ability for soybean isoflavone glycosides and glucose-tolerance from soil metagenomic library

A novel β-glucosidase (Bgl1269) was identified from a metagenomic library of mangrove soil by activity-based functional screening. Sequence analysis revealed that Bgl1269 encodes a protein of 422 amino acids. After being overexpressed in Escherichia coli and purified, the enzymatic properties of Bgl1269 were investigated. The recombinant enzyme displayed a pH optimum of 6.0 and a temperature optimum of 40°C, and the addition of most common metal ions (1 or 10mM) increased the enzymatic activity evidently. In addition, the enzyme showed high hydrolyzing ability for soybean isoflavone glycosides, and 0.8unit of enzyme could completely converted daidzin and genistin (0.5mg/mL) to daidzein and genistein at 40°C for 0.5h. Interestingly, Bgl1269 also exhibited a very high glucose-tolerance, with the highest inhibition constant K(i) (4.28M) among β-glucosidases reported so far. These properties make it a good candidate in the production of soybean isoflavone aglycones after further study.

Biochemical properties of a novel glycoside hydrolase family 1 β-glucosidase (PtBglu1) from Paecilomyces thermophila expressed in Pichia pastoris

A novel β-glucosidase gene (PtBglu1) from the thermophilic fungus, Paecilomyces thermophila, was cloned and expressed in Pichia pastoris. PtBglu1 contained an open reading frame of 1440-bp nucleotides and encoded a protein of 479 amino acids which showed significant similarity to other fungal β-glucosidases from glycoside hydrolase (GH) family 1. The recombinant β-glucosidase (PtBglu1) was secreted at high level of 190.2 U mL(-1) in high cell density fermentor (5L). PtBglu1 was purified to homogeneity, and was found to be a glycoprotein with molecular mass of 56.7 kDa. The purified PtBglu1 showed optimum catalytic activity at pH 6.0 and 55 °C. The enzyme exhibited broad substrate specificity with highest activity toward pNP-β-D-glucopyranoside, followed by pNP-β-D-galactopyranoside and cellobiose. The K(m) values for pNP-β-D-glucopyranoside, cellobiose, gentiobiose and salicin were 0.55 mM, 1.0 mM, 1.74 mM and 6.85 mM, respectively. These properties make PtBglu1 a potential candidate for various industrial applications.