A Bi-enzymatic Immobilized Nanobiocatalyst for the Biotransformation of Oleuropein to Hydroxytyrosol

Multi-enzymatic assemblies offer the opportunity of bringing in proximity several enzymes that are enabled to work together for the catalysis of multi-step reactions. Especially, the development of robust nanobiocatalytic systems comprising of several enzymes has gained considerable attention over the last few years for the catalysis of complex reactions and the production of high added-value products. In the present chapter, we describe the methodology for the development of a bi-enzymatic nanobiocatalyst consisting of the enzymes β-glucosidase from Thermotoga maritima and lipase A from Candida antarctica (CalA) co-immobilized on chitosan-coated magnetic nanoparticles. This nanobiocatalyst can be efficiently applied for the biotransformation of oleuropein to hydroxytyrosol, a reaction of increased biotechnological interest. Several techniques, as well as methodologies that are required for the characterization of the structure and the activity of such systems are also comprehensively described.

Improving the Substrate Affinity and Catalytic Efficiency of β-Glucosidase Bgl3A from Talaromyces leycettanus JCM12802 by Rational Design

Improving the substrate affinity and catalytic efficiency of β-glucosidase is necessary for better performance in the enzymatic saccharification of cellulosic biomass because of its ability to prevent cellobiose inhibition on cellulases. Bgl3A from Talaromyces leycettanus JCM12802, identified in our previous work, was considered a suitable candidate enzyme for efficient cellulose saccharification with higher catalytic efficiency on the natural substrate cellobiose compared with other β-glucosidase but showed insufficient substrate affinity. In this work, hydrophobic stacking interaction and hydrogen-bonding networks in the active center of Bgl3A were analyzed and rationally designed to strengthen substrate binding. Three vital residues, Met36, Phe66, and Glu168, which were supposed to influence substrate binding by stabilizing adjacent binding site, were chosen for mutagenesis. The results indicated that strengthening the hydrophobic interaction between stacking aromatic residue and the substrate, and stabilizing the hydrogen-bonding networks in the binding pocket could contribute to the stabilized substrate combination. Four dominant mutants, M36E, M36N, F66Y, and E168Q with significantly lower K_m values and 1.4–2.3-fold catalytic efficiencies, were obtained. These findings may provide a valuable reference for the design of other β-glucosidases and even glycoside hydrolases.

A Novel Neutral and Mesophilic β-Glucosidase from Coral Microorganisms for Efficient Preparation of Gentiooligosaccharides

β-glucosidases can produce gentiooligosaccharides that are lucrative and promising for the prebiotic and alternative food industries. However, the commercial production of gentiooligosaccharides using β-glucosidase is challenging, as this process is limited by the need for high thermal energy and increasing demand for the enzyme. Here, a putative β-glucosidase gene, selected from the coral microbial metagenome, was expressed in Escherichia coli. Reverse hydrolysis of glucose by Blg163 at pH 7.0 and 40 °C achieved a gentiooligosaccharide yield of 43.02 ± 3.20 g·L⁻¹ at a conversion rate of 5.38 ± 0.40%. Transglycosylation of mixed substrates, glucose and cellobiose, by Blg163 consumed 21.6 U/0.5 g glucose/g cellobiose, achieving a gentiooligosaccharide yield of 70.34 ± 2.20 g·L⁻¹ at a conversion rate of 15.63%, which is close to the highest yield reported in previous findings. Blg163-mediated synthesis of gentiooligosaccharides is the mildest reaction and the lowest β-glucosidase consumption reported to date.

Contrasting Effects of Environmental Concentrations of Sulfonamides on Microbial Heterotrophic Activities in Freshwater Sediments

The sulfonamide antibiotics sulfamethoxazole (SMX) and sulfamethazine (SMZ) are regularly detected in surface sediments of contaminated hydrosystems, with maximum concentrations that can reach tens of μg kg^–1 in stream and river sediments. Little is known about the resulting effects on the exposed benthic organisms. Here we investigated the functional response of stream sediment microbial communities exposed for 4 weeks to two levels of environmentally relevant concentrations of SMX and SMZ, tested individually. To this end, we developed a laboratory channel experiment where natural stream sediments were immersed in water contaminated with nominal environmental concentrations of 500 and 5,000 ng L^–1 of SMX or SMZ, causing their accumulation in surface sediments. The mean maximum concentrations measured in the sediment (about 2.1 μg SMX kg^–1 dw and 4.5 μg SMZ kg^–1 dw) were consistent with those reported in contaminated rivers. The resulting chronic exposure had various effects on the functional potential of the sediment microbial communities, according to the substance (SMX or SMZ), the type of treatment (high or low) and the measured activity, with a strong influence of temporal dynamics. Whereas the SMZ treatments resulted in only transient effects on the five microbial activities investigated, we observed a significant stimulation of the β-glucosidase activity over the 28 days in the communities exposed to the high concentration of SMX. Together with the stimulation of aerobic respiration at low SMX concentrations and the reduced concentration observed in the last days, our results suggest a potential biodegradation of sulfonamides by microbial communities from sediments. Given the key functional role of surface sediment microbial communities in streams and rivers, our findings suggest that the frequently reported contamination of sediments by sulfonamides is likely to affect biogeochemical cycles, with possible impact on ecosystem functioning.

Evaluation of the inhibitory potentials of selected compounds from Costus spicatus (Jacq.) rhizome towards enzymes associated with insulin resistance in polycystic ovarian syndrome: an in silico study

Background

Polycystic ovary syndrome (PCOS) is a chronic endocrine disorder prevalent in premenopausal women and is characterized by a range of physiological and biochemical abnormalities which may include reproductive, endocrine, and metabolic alterations such as insulin resistance. Insulin resistance is the hallmark of PCOS as it predisposes the affected subjects to a higher risk of impaired glucose tolerance and type 2 diabetes mellitus (T2DM). In this study, the inhibitory activities of phytosterols and saccharides from aqueous extract of Costus spicatus rhizome were investigated against phosphoenolpyruvate carboxykinase (PEPCK), α-amylase, β-glucosidase, and fructose 1,6-biphosphatase (FBPase) in silico as potential novel therapeutic targets for T2DM-associated-PCOS. Phytochemical constituents of the plant were determined using gas chromatography-mass spectrophotometry (GC-MS), while molecular docking of the compounds with PEPCK, α-amylase, β-glucosidase, and FBPase was conducted using Vina. Thereafter, the binding modes were determined using Discovery Studio Visualizer, 2020.

Results

GCMS analysis of an aqueous extract of Costus spicatus rhizome revealed the presence of three compounds with a higher binding affinity for all enzymes studied compared to metformin. The compounds also interacted with key amino acid residues crucial to the enzyme’s activities. This study identified Lyxo-d-manno-nononic-1,4-lactone as potential multi-target inhibitors of PEPCK, α-amylase, β-glucosidase, and FBPase with reasonable pharmacokinetic properties and no significant toxicity.

Conclusion

These compounds can be explored as potential therapeutic agents for the management of insulin resistance in PCOS, subject to further experimental validation.

The extracellular β-glucosidase BGL2 has two variants with different molecular sizes and hydrolytic activities in the stipe or pilei of Coprinopsis cinerea

Two variants of extracellular β-glucosidase (BGL2) were purified from the stipe and pilei of Coprinopsis cinerea. In the stipe, BGL2 was a monomeric protein with an apparent molecular mass of approximately 220 kDa, representing a mature full-length peptide of BGL2. However, in the pilei, the apparent molecular mass of BGL2 was only approximately 120 kDa, consisting of the 60 kDa N-terminal fragment and 55 kDa C-terminal fragment. The hydrolytic activities of BGL2 purified from the pilei were higher than those of BGL2 purified from the stipe. No mRNA splice variants of bgl2 were detected. Therefore, the different variants of BGL2 in the stipe and pilei were not formed by differential RNA splicing. Furthermore, in vitro experiments showed that full-length BGL2 could be cleaved by endogenous proteases from pilei or commercial trypsin at a similar site to form an oligomeric protein consisting of the N-terminal fragment and C-terminal fragment similar to BGL2 from pilei. The hydrolytic activity of BGL2 increased after cleavage by those proteases in vitro. We conclude that the 120 kDa variant of BGL2 in the pilei of C. cinerea is formed by posttranslational proteolytic cleavage. Posttranslational proteolytic cleavage is an efficient way to regulate the activity of BGL2 to adapt to the needs of different physiological functions in the elongation stipe and expansion pilei of C. cinerea.

Screening and characterization of a GH78 α-l-rhamnosidase from Aspergillus terreus and its application in the bioconversion of icariin to icaritin with recombinant β-glucosidase

In this study, a GH78 α-L-rhamnosidase AtRha from Aspergillus terreus CCF3059 was screened and expressed in Pichia pastoris KM71H. The maximum enzyme activity of AtRha was 1000 U/mL after 12 days. AtRha was most active at 65 °C and pH 6.5, displaying excellent thermal stability and pH stability. The kinetic parameters Km, Vmax, kcat and kcat/Km values for pNPR were 0.481 mM, 659 μmol/min·mg, 1065 s-1 and 2214 s-1mM-1, respectively. AtRha could be inhibited by Fe2+, Hg2+ and Cu2+. Moreover, it displayed good tolerance to organic reagents with 52.6% activity in 15%(w/v) methanol. AtRha can hydrolyze icariin containing the α-1 rhamnoside linkage. Furthermore, AtRha and β-glucosidase TthBg3 showed excellent selectivity to cleave the rhamnose at the 3rd position and the glucosyl at the C-7 group of icariin, which established an effective and green method to produce the more pharmacological active icaritin. In addition, the optimal enzyme addition schemes and the reaction conditions were screened and optimized. After a two-stage transformation under optimized conditions, 0.5 g/L of icariin was transformed into 0.25 g/L of icaritin, with a corresponding molar conversion rate of 91.2%. Our findings provide a new, specific and cost-effective method for the production of icaritin in the industry.

Expression of a β-glucosidase from Trichoderma reesei in Escherichia coli using a synthetic optimized gene and stability improvements by immobilization using magnetite nano-support

The enzymatic conversion of lignocellulosic biomass to fermentable sugars is determined by the enzymatic activity of cellulases; consequently, improving enzymatic activity has attracted great interest in the scientific community. Cocktails of commercial cellulase often have low β-glucosidase content, leading to the accumulation of cellobiose. This accumulation inhibits the activity of the cellulolytic complex and can be used to determine the enzymatic efficiency of commercial cellulase cocktails. Here, a novel codon optimized β-glucosidase gene (B-glusy) from Trichoderma reesei QM6a was cloned and expressed in three strains of Escherichia coli (E. coli). The synthetic sequence containing an open reading frame (ORF) of 1491 bp was used to encode a polypeptide of 497 amino acid residues. The β-glucosidase recombinant protein that was expressed (57 kDa of molecular weight) was purified by Ni agarose affinity chromatography and visualized by SDS-PAGE. The recombinant protein was better expressed in E. coli BL21 (DE3), and its enzymatic activity was higher at neutral pH and 30 °C (22.4 U/mg). Subsequently, the β-glucosidase was immobilized using magnetite nano-support, after which it maintained >65% of its enzymatic activity from pH 6 to 10, and was more stable than the free enzyme above 40 °C. The maximum immobilization yield had enzyme activity of 97.2%. In conclusion, β-glucosidase is efficiently expressed in the microbial strain E. coli BL21 (DE3) grown in a simplified culture medium.

Enzymatic control and evaluation of degrees of polymerization of β-(1→2)-glucans

β-(1 → 2)-Glucans can be synthesized by 1,2-β-oligoglucan phosphorylase using β-(1 → 2)-glucooligosaccharides as acceptors and α-d-glucose 1-phosphate as a donor. Using phosphorolysis of sucrose as a source of α-d-glucose 1-phosphate, we generated β-(1 → 2)-glucans with degrees of polymerization (DPs) up to approximately 280. Average DPs up to approximately 1000 were obtained using β-(1 → 2)-glucan with average DP of 160 as an acceptor and pure α-d-glucose 1-phosphate as a donor. A colorimetric assay of the β-glucosidase activity against the β-(1 → 2)-glucan products was used to determine their DPs.

A Novel β-Glucosidase From Chryseobacterium scophthalmum 1433 for Efficient Rubusoside Production From Stevioside

As a natural sweetening and solubilizing agent, rubusoside has great potential in the application of healthy beverages and pharmaceuticals. However, the direct extraction and purification of rubusoside from raw materials is inefficient. In this work, a novel β-glucosidase (CsBGL) was obtained from Chryseobacterium scophthalmum 1433 through screening of the environmental microorganisms. CsBGL markedly hydrolyzed sophorese (Glcβ1-2Glc) and laminaribiose (Glcβ1-3Glc), but for steviol glycosides, it only hydrolyzed the C-13/C-19-linked sophorese, instead of the C-13/C-19-linked Glcβ1-2[Glcβ1-3]Glc trisaccharide and Glcβ1-monosaccharide. It efficiently hydrolyzed stevioside (240 g/L) to produce rubusoside (99% yield) at 47.5°C for 70 min. Even when using a crude steviol glycosides extract (500 g/L) containing ∼226 g/L stevioside as the substrate, CsBGL could also convert stevioside to rubusoside (99% yield) at 47.5°C for 2 h, in which the rubusoside concentration increased from the initial 42 g/L to the final 222 g/L. These results reveal that CsBGL would be a promising biocatalyst for the industry-scale production of rubusoside from stevioside or/and the crude steviol glycosides extract.

A beta-glucosidase of an insect herbivore determines both toxicity and deterrence of a dandelion defense metabolite

Gut enzymes can metabolize plant defense compounds and thereby affect the growth and fitness of insect herbivores. Whether these enzymes also influence feeding preference is largely unknown. We studied the metabolization of taraxinic acid β-D-glucopyranosyl ester (TA-G), a sesquiterpene lactone of the common dandelion (Taraxacum officinale) that deters its major root herbivore, the common cockchafer larva (Melolontha melolontha). We have demonstrated that TA-G is rapidly deglucosylated and conjugated to glutathione in the insect gut. A broad-spectrum M. melolontha β-glucosidase, Mm_bGlc17, is sufficient and necessary for TA-G deglucosylation. Using cross-species RNA interference, we have shown that Mm_bGlc17 reduces TA-G toxicity. Furthermore, Mm_bGlc17 is required for the preference of M. melolontha larvae for TA-G-deficient plants. Thus, herbivore metabolism modulates both the toxicity and deterrence of a plant defense compound. Our work illustrates the multifaceted roles of insect digestive enzymes as mediators of plant-herbivore interactions.

Plants produce certain substances to fend off attackers like plant-feeding insects. To stop these compounds from damaging their own cells, plants often attach sugar molecules to them. When an insect tries to eat the plant, the plant removes the stabilizing sugar, ‘activating’ the compounds and making them toxic or foul-tasting. Curiously, some insects remove the sugar themselves, but it is unclear what consequences this has, especially for insect behavior.

Dandelions, Taraxacum officinale, make high concentrations of a sugar-containing defense compound in their roots called taraxinic acid β-D-glucopyranosyl ester, or TA-G for short. TA-G deters the larvae of the Maybug – a pest also known as the common cockchafer or the doodlebug – from eating dandelion roots. When Maybug larvae do eat TA-G, it is found in their systems without its sugar. However, it is unclear whether it is the plant or the larva that removes the sugar. A second open question is how the sugar removal process affects the behavior of the Maybug larvae.

Using chemical analysis and genetic manipulation, Huber et al. investigated what happens when Maybug larvae eat TA-G. This revealed that the acidity levels in the larvae’s digestive system deactivate the proteins from the dandelion that would normally remove the sugar from TA-G. However, rather than leaving the compound intact, larvae remove the sugar from TA-G themselves. They do this using a digestive enzyme, known as a beta-glucosidase, that cuts through sugar. Removing the sugar from TA-G made the compound less toxic, allowing the larvae to grow bigger, but it also increased TA-G’s deterrent effects, making the larvae less likely to eat the roots.

Any organism that eats plants, including humans, must deal with chemicals like TA-G in their food. Once inside the body, enzymes can change these chemicals, altering their effects. This happens with many medicines, too. In the future, it might be possible to design compounds that activate only in certain species, or under certain conditions. Further studies in different systems may aid the development of new methods of pest control, or new drug treatments.

Directional bioconversion and optimization of stevioside into rubusoside by Lelliottia sp. LST-1

AIMS

The present study aimed to specifically transform stevioside (ST) into rubusoside (RS) through bioconversion with high efficiency, seeking to endow steviol glycosides (SGs) with subtle flavours for commercial acceptability.

METHODS AND RESULTS

An endophytic bacterium named Lelliottia LST-1 was screened and confirmed to specifically convert ST into RS, reaching a conversion rate of 75.4% after response surface optimization. Phylogenetic analysis combined with complete genome sequencing demonstrated that LST-1 was also presumed to be a new species. To further explore the principle and process of biological transformation, the potential beta-glucosidases GH3-1, GH3-2, GH3-3 and GH3-4 were expressed, purified and reacted with SGs. High-performance liquid chromatography revealed that all enzymes hydrolysed ST and generated RS, but substrate specificity analysis indicated that GH3-2 had the highest substrate specificity towards STs and the highest enzyme activity.

CONCLUSION

The potential β-glucosidase GH3-2 in Lelliottia sp. LST-1 was found to specifically and efficiently convert ST to RS.

SIGNIFICANCE AND IMPACT OF STUDY

The efficient biotransformation of ST into RS will be beneficial to its large-scale production and extensive application in the food and pharmaceutical industries.

Effect of fruit thermal processing on ethyl carbamate content in maesil (Prunus mume) liqueur

The thermal effect of maesil on the content of ethyl carbamate and its precursors during one-year ripening of maesil liqueur was investigated. Fresh maesil (control), fruit blanched for 2 min (blanched), and fruit blanched and dried for 15 h at 50 °C (blanched/dried) were soaked in the liquor containing 25% alcohol at a ratio of 1:2 (w/w) for 100 days at 25 °C and the liquid was further ripened for 260 days. Ethyl carbamate ranged from 13.1 to 204.4 μg/kg with the highest value at 210 day. Thermally treated samples had higher ethyl carbamate concentration than the control, suggesting that thermal treatment increased the formation of ethyl carbamate. A positive correlation between ethyl carbamate content and β-glucosidase activity in all samples indicated that enzymatic hydrolysis of amygdalin by β-glucosidase determined ethyl carbamate concentration during the fermentation of maesil liqueur.

Coordinated β-glucosidase activity with the cellulosome is effective for enhanced lignocellulose saccharification

Consolidated bio-saccharification (CBS) technology employs cellulosome-producing bacterial cells, rather than fungal cellulases, as biocatalysts for cost-effective production of lignocellulosic sugars. Extracellular β-glucosidase (BGL) expression in the whole-cell arsenal is indispensable, due to severe cellobiose inhibition of the cellulosome. However, high-level BGL expression in Clostridium thermocellum is challenging, and the optimal BGL production level for efficient cellulose saccharification is currently unknown. Herein, we obtained new CBS biocatalysts by transforming BGL-expressing plasmids into C. thermocellum, which produced abundant BGL proteins and hydrolyzed cellulose effectively. The optimal ratio of extracellular BGL-to-cellulosome activity was determined to be in a range of 5.5 to 21.6. Despite the critical impact of BGL, both excessive BGL expression and its assembly on the cellulosome via type I cohesin-dockerin interaction led to reduced cellulosomal activity, which further confirmed the importance of coordinated BGL expression with the cellulosome. This study will further promote industrial CBS application in lignocellulose conversion.

Study of the olive β-glucosidase gene family putatively involved in the synthesis of phenolic compounds of virgin olive oil

BACKGROUND

Hydrolysis of the fruit phenolic glucosides occurring during the oil extraction process is the main biochemical reaction affecting the biosynthesis and accumulation of secoiridoid compounds in virgin olive oil. An integrated approach at the molecular, biochemical, and metabolic level was used to study the olive β-glucosidase gene family in seven olive cultivars selected by their different phenolic profiles.

RESULTS

Eight β-glucosidase genes have been identified by in silico analysis of an olive transcriptome. Their expression levels were analyzed by reverse transcription quantitative polymerase chain reaction in olive fruits at different ripening stages: I, green fruits, 16-19 weeks after flowering (WAF); II, yellow-green fruits, 22-25 WAF; III, turning fruits, 28-31 WAF; and IV, fully ripe fruits, 35-40 WAF. Gene expression was compared with the level of β-glucosidase activity in the fruit and with the phenolic composition of fruits and oils from different olive cultivars. Phylogenetic analysis of the encoded proteins and differences found among the β-glucosidase genes based on Gene Ontology enrichment analysis data suggests maximum involvement of two genes, OeBGLU1A and OeBGLU1B, in the phenolic composition of virgin olive oil. Positive correlation coefficients were found within each olive cultivar between OeBGLU1A and OeBGLU1B gene expression data and the phenolic content of the oil.

CONCLUSION

The results obtained suggest that the expression pattern of specific β-glucosidase genes may be an accurate predictor for the phenolic content of virgin olive oil that could be used in olive breeding programs. © 2021 Society of Chemical Industry.

The Impact of the Fermentation Strategy on the Flavour Formation of Ilzer Rose (Malus domestica Borkh.) Apple Wine

The flavour and the volatilome of apple wines made from the Austrian heritage variety Ilzer Rose was in the scope of this study. The apple wines were produced by adopting oenological practises that are not commonly used in fruit wine production. Different fermentation strategies including the addition of enzymes with β-glucosidase activity, addition of a fining agent, maceration of the mash along with mash fermentation were applied. The volatile compounds of the juices as intermediates and the resulting apple wines were analysed using headspace-SPME GC-MS. CATA technique with a well-trained panel was applied for sensory evaluation. The results show that the flavour of single-variety apple wine can be significantly altered by taking oenological measures. High correlations were found between the results of the analytical investigation and the sensory evaluation. Maceration of the mash leads to an increase in the fruity character of the products, also reflected by significantly higher fruit ester quantities in the wine. During mash fermentation, spontaneous malolactic fermentation was induced leading to a product with new, but thoroughly interesting sensory properties of the apple wine. The results of this study demonstrate that the integration of oenological measures may open a wide field to the development of a high diversity in apple wine flavour.

Conditions of enzyme-assisted extraction to increase the recovery of flavanone aglycones from pectin waste

The citrus pectin by-product (CPB), generated from pectin industry, is a rich-source of flavanones, but not explored until now. As most of these compounds are inside vacuoles or bound to cell wall matrix, enzymatic hydrolysis was applied on their recovery, followed by hydroalcoholic and ultrasound extraction. Different parameters were studied: enzymes (β-glucosidase, tannase, and cellulase), their concentration (5, 10, and 20 U g^-1 CPB), and reaction time (6, 12, and 24 h). Extracts were characterized in total phenolic content (TPC), antioxidant capacity (ORAC and DPPH assays), and polyphenolic profile (HPLC-DAD). All enzymatic treatments significantly improved CPB antioxidant capacity and TPC, compared with hydroalcoholic and ultrasound extraction. β-glucosidase (5 U) for 24 h was the most effective in polyphenol extraction and bioconversion, followed by β-glucosidase (5 U) for 12 h and tannase (5 U) for 24 h. Thus, the concentration of these enzymes was increased (10 and 20 U) to improve flavanones extraction. β-glucosidase at 20 U offered the highest amount of naringenin (77.63 mg 100 g^-1 of CPB) and hesperetin (766.44 mg 100 g^-1) obtained so far by biological processes. According to Person's correlation analysis, TPC and antioxidant activity were highly correlated with CPB contents of hesperetin and naringenin. The aglycone flavanones are rarely found in natural sources and have higher biological potential than their glycosylated forms. Our results indicated enzyme-assisted extraction as a good choice for recovering aglycone flavanones from CPB, and increased knowledge on the biological activity of this agroindustrial waste, amplifying their application in food and pharmaceutical field.

Enzyme activities in a sandy soil of Western Bahia under cotton production systems: short-term effects, temporal variability, and the FERTBIO sample concept

Enzyme activities (EAs) and the FERTBIO sample concept have been increasingly adopted as a novel approach to estimate the soil quality in Brazil. However, the performance of this strategy in sandy soils of the Cerrado biome remains unclear. During 2 years, in a Cerrado's sandy soil, the short-term effects of ten different cropping systems (conventional tillage or no-tillage associated with monoculture, rotations, and/or successions) on the activities of β-glucosidase, acid phosphatase, and arylsulfatase were studied. Issues related to annual variability and the feasibility of using the FERTBIO sample concept for soil enzymes activities were also evaluated. Soil samples were collected at three different depths (0-10 cm, 10-20 cm, and 20-40 cm) in March 2017 and February 2018. Five years since the beginning of the experiment, the presence of cover crops and no-till promoted improvements in EAs evidencing the importance of regenerative management practices for the sustainability of agroecosystems in sandy soils. Regardless of the cropping systems and depths evaluated, soil organic carbon and EAs showed low temporal variation during the 2 years of monitoring. Our results also showed that it is possible to use the FERTBIO sample concept for the Quartzipsament soils of Western Bahia, Brazil.

Expression of heat-resistant β-glucosidase in Escherichia coli and its application in the production of gardenia blue

Gardenia blue is a natural blue pigment that is environmentally friendly, non-toxic, and stable. The hydrolysis of geniposide, catalyzed by β-glucosidase, is a critical step in the production process of gardenia blue. However, β-glucosidase is not resistant to high temperatures, limiting the production of gardenia blue. In this study, we investigated the effectiveness of a heat-resistant glucosidase obtained from Thermotoga maritima in the production of gardenia blue. The enzyme exhibited a maximum activity of 10.60 U/mL at 90 °C. Single-factor and orthogonal analyses showed that exogenously expressed heat-resistant glucosidase reacted with 470.3 μg/mL geniposide and 13.5 μg/mL glycine at 94.2 °C, producing a maximum yield of 26.2857 μg/mL of gardenia blue after 156.6 min. When applied to the dyeing of denim, gardenia blue produced by this method yielded excellent results; the best color-fastness was achieved when an iron ion mordant was used. This study revealed the feasibility and application potential of microbial production of gardenia blue.

Silencing of Oleuropein β-Glucosidase Abolishes the Biosynthetic Capacity of Secoiridoids in Olives

Specialized metabolism is an evolutionary answer that fortifies plants against a wide spectrum of (a) biotic challenges. A plethora of diversified compounds can be found in the plant kingdom and often constitute the basis of human pharmacopeia. Olive trees (Olea europaea) produce an unusual type of secoiridoids known as oleosides with promising pharmaceutical activities. Here, we transiently silenced oleuropein β-glucosidase (OeGLU), an enzyme engaged in the biosynthetic pathway of secoiridoids in the olive trees. Reduction of OeGLU transcripts resulted in the absence of both upstream and downstream secoiridoids in planta, revealing a regulatory loop mechanism that bypasses the flux of precursor compounds toward the branch of secoiridoid biosynthesis. Our findings highlight that OeGLU could serve as a molecular target to regulate the bioactive secoiridoids in olive oils.

Oenological Characteristics of Four Non-Saccharomyces Yeast Strains With β-Glycosidase Activity

Non-Saccharomyces yeast with β-glucosidase activity might positively contribute to the flavor and quality of wines. The contribution of four non-Saccharomyces yeast strains Issatchenkia terricola SLY-4, Pichia kudriavzevii F2-24, P. kudriavzevii F2-16, and Metschnikowia pulcherrima HX-13 with β-glucosidase activity to the flavor and quality of wine making was studied. Compared with those of S. cerevisiae single fermentation, the four non-Saccharomyces yeast strains could grow and consume sugar completely with longer fermentation periods, and with no significantly negative effect on chemical characteristics of wines. Moreover, they produced lower content of C6 compounds, benzene derivative, and fatty acid ethyl ester compounds and higher content of terpene, β-ionone, higher alcohol, and acetate compounds. Different yeast strains produced different aroma compounds profiles. In general, the sensory evaluation score of adding non-Saccharomyces yeast-fermented wine was better than that of S. cerevisiae, and I. terricola SLY-4 fermentation received the highest one, followed by P. kudriavzevii F2-24, P. kudriavzevii F2-16, and M. pulcherrima HX-13 from high to low. The research results provide a theoretical basis for the breeding of non-Saccharomyces yeast and its application in wine making.

Effects of novel flavonoid-enriched yogurt on the diversity of intestinal microbiota in mice

Soy isoflavone glycoside cannot be effectively absorbed by the human intestinal tract, but probiotics with related hydrolases can transform it into aglycone to promote its absorption. In this study, a novel flavonoid-enriched yogurt was developed using an isolated β-glucosidase-producing strain (Lactiplantibacillus plantarum GY). The flavonoid aglycone-enhanced yogurt was fed to ICR mice for 21 days, and its effects were observed. The yogurt can affect the gut microbial diversity of mice, especially increasing the abundance of Parasutterella, the Bacteroidales S24-7 group, and Phascolarctobacterium in the intestinal tract of mice. Meanwhile, the ratio of Bacteroidetes/Firmicutes in the intestinal tract of mice fed with the flavonoid aglycone-enriched yogurt increased. The difference in the content of butyric acid between the L-GY + IS and the control groups was significant (P < 0.05). Therefore, milk fermentation with β-glucosidase-producing strains is a promising approach for developing flavonoid glycoside-enriched yogurt products.

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

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

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

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

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

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