Article on beta-fructofuranosidases and polyphenols published in Scientific Reports

Enzymatic glycosylation of polyphenols is a tool to improve their physicochemical properties and bioavailability. On the other hand, glycosidic enzymes can be inhibited by phenolic compounds. In this work, we studied the specificity of various phenolics (hydroquinone, hydroxytyrosol, epigallocatechin gallate, catechol and p-nitrophenol) as fructosyl acceptors or inhibitors of the β-fructofuranosidase from Xanthophyllomyces dendrorhous (pXd-INV). Only hydroquinone and hydroxytyrosol gave rise to the formation of glycosylated products. For the rest, an inhibitory effect on both the hydrolytic (H) and transglycosylation (T) activity of pXd-INV was observed. To disclose the binding mode of each compound and elucidate the molecular features determining its acceptor or inhibitor behaviour, ternary complexes of the inactive mutant pXd-INV-D80A with fructose and the different polyphenols were analyzed by X-ray crystallography. All the compounds bind by stacking against Trp105 and locate one of their phenolic hydroxyls making a polar linkage to the fructose O2 at 3.6–3.8 Å from the C2, which could enable the ulterior nucleophilic attack leading to transfructosylation. The acceptor capacity of the different polyphenols seems mediated by their ability to make flexible polar links with the protein.

Ref.: “Deciphering the molecular specificity of phenolic compounds as inhibitors or glycosyl acceptors of β fructofuranosidase from Xanthophyllomyces dendrorhous”. M. Ramirez-Escudero, N. Miguez, M. Gimeno-Perez, A.O. Ballesteros, M. Fernandez-Lobato, F.J. Plou* and J. Sanz-Aparicio* Scientific Reports 9, 17441 (2019), doi:10.1038/s41598-019-53948-y

Production of isomelezitose by Metschnikowia reukaufii cell extracts

Metschnikowia reukaufii is a widespread yeast able to grow in the floral nectaries, an environment of extreme conditions with sucrose concentrations exceeding 400 g l−1, which led us into the search for enzymatic activities involved in this sugar transformation. New oligosaccharides were produced by transglucosylation processes employing M. reukaufii cell extracts in overload‐sucrose reactions. These products were purified and structurally characterized by MS‐ESI and NMR . The reaction mixture included new sugars showing a great variety of glycosidic bonds including α‐(1→1), α‐(1→3) and α‐(1→6) . The main product synthesized was the trisaccharide isomelezitose, whose maximum concentration reached 81 g l−1, the highest amount reported for any unmodified enzyme or microbial extract. In addition, 51 g l−1 of the disaccharide trehalulose was also produced. Both sugars show potential nutraceutical and prebiotic properties. The sugar mixture obtained in the biosynthetic reactions also contained oligosaccharides such as esculose, a rare trisaccharide. as well as erlose, melezitose and theanderose. All the sugars produced are naturally found in honey. These compounds are of biotechnological interest due to their potential food, cosmeceutical and pharmaceutical applications.

Ref.: M. Garcia-Gonzalez, F.V. Cervantes, F.J. Plou, M. Remacha, A. Poveda, J. Jimenez-Barbero and M. Fernandez-Lobato. “Efficient production of isomelezitose by a novel glucosyltransferase activity in Metschnikowia reukaufii cell extracts”. Microbial Biotechnology (2019), doi:10.1111/1751-7915.13490

Production of High Fructose Syrup (HFS) with immobilized glucose isomerase published in Food Chemistry

In collaboration with University of Sfax (Tunisia) and University of Sciences and Technology of Houari Boumediene (Algeria), we have investigated the glucose isomerase (GICA) from Caldicoprobacter algeriensis. The enzyme was immobilized by ionic adsorption on polymethacrylate carriers. The Sepabeads EC-HA yielded the highest recovery of activity (89%). The adsorbed enzyme displayed higher relative activity at acidic pH, greater thermostability, and better storage stability, compared to the free form. Moreover, the immobilized enzyme showed an excellent operational stability, in 15 successive 3h reaction cycles at 85°C under a batch reactor, preserving 83% of its initial activity. Interestingly, a continuous process for High Fructose Syrup (HFS) production was established with the adsorbed GICA using a packed bed reactor during eleven days at 70°C. HPAEC-PAD analysis showed a maximum bioconversion rate of 49% after 48h of operation.

Reference: "Immobilization of the glucose isomerase from Caldicoprobacter algeriensis on Sepabeads EC-HA and its efficient application in continuous High Fructose Syrup production using packed bed reactor". S. Neifar, F.V. Cervantes, H. BenHlima, A. Bouanane-Darenfed, A.O. Ballesteros, F.J. Plou, S. Bejar. . Food Chemistry (2019), doi: 10.1016/j.foodchem.2019.125710

Enzymatic synthesis and surfactant properties of tert-butyl α-D-glucopyranosides

While testing the ability of cyclodextrin glucanotransferases (CGTases) to glucosylate a series of flavonoids in the presence of organic cosolvents, we found out that this enzyme was able to glycosylate a tertiary alcohol (tert-butyl alcohol). Two glycosylation products were characterized by mass spectrometry (MS) and nuclear magnetic resonance (NMR) as tert-butyl-α-D-glucoside (major product) and tert-butyl-α-D-maltoside (minor product). Using partially hydrolyzed starch as glucose donor, the yield of transglucosylation was approximately 44%. The synthesized tert-butyl-α-D-glucoside exhibited the typical surfactant behavior (critical micellar concentration, 4.0–4.5 mM) and its properties compared well with those of the related octyl-α-D-glucoside. To the best of our knowledge, this is the first description of an enzymatic α-glucosylation of a tertiary alcohol.

Reference; ''Production and Surfactant Properties of Tert-Butyl α-D-Glucopyranosides Catalyzed by Cyclodextrin Glucanotransferase'' H. Garcia-Arellano, J. L. Gonzalez-Alfonso, C. Ubilla, F. Comelles, M. Alcalde, M. Bernabé, J-L Parra, A. O. Ballesteros and F. J. Plou. Catalysts  (2019), https://doi.org/10.3390/catal9070575

Foundation Ramón Areces Grant

One of the members of GLICOENZ consortium, Prof. María Fernández Lobato, has obtained a grant  by Foundation Ramón Areces  in the XIX Call of Research Grants in Life and Materials Sciences. The project will be focused on bioactive properties of oligosaccharides and glycoderivatives, including biomedical applications.

Enzymatic glucosylation of hesperetin with CGTase.

The regioselective α -glucosylation of hesperetin was achieved by a transglycosylation reaction catalyzed by cyclodextrin glucanotransferase (CGTase) from Thermoanaerobacter sp. using soluble starch as glucosyl donor. By combining mass spectrometry (ESI-TOF) and 2D-NMR analysis, the main monoglucosylated derivative was fully characterized (hesperetin 7-O-α-D-glucopyranoside).
In order to increase the yield of monoglucoside, several reaction parameters were optimized: Nature and percentage of cosolvent, composition of the aqueous phase, glucosyl donor, temperature, and the concentrations of hesperetin and soluble starch. Under the optimal conditions, which included the presence of 30% of bis(2-methoxyethyl) ether as cosolvent, the maximum concentration of monoglucoside was approximately 2 mM, obtained after 24 h of reaction. To our knowledge, this is the first report of direct glucosylation of hesperetin employing free enzymes instead of whole cells.

Ref. J.L. González-Alfonso, N. Míguez, J. D. Padilla, L. Leemans, A. Poveda, J. Jimnez-Barbero, A. O. Ballesteros, G. Sandoval and F. J. Plou. ''Optimization of Regioselective Glucosylation of Hesperetin Catalyzed by Cyclodextrin Glucanotransferase'' . Molecules, 23, 2285, (2018) doi: 10.3390/molecules23112885

Immobilization techniques of the β-fructofuranosidase from Xanthophyllomyces dendrorhous published in Catalysts.

The β-fructofuranosidase (Xd-INV) from the basidiomycota yeast Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma) is unique in its ability to synthesize neo- fructooligosaccharides (neo-FOS). In order to facilitate its industrial application, the recombinant enzyme expressed in Pichia pastoris(pXd-INV) was immobilized by entrapment in polyvinyl alcohol (PVA) hydrogels. The encapsulation efficiency exceeded 80%. The PVA lenticular particles of immobilized pXd-INV were stable up to approximately 40 °C. Using 600 g/L sucrose, the immobilized biocatalyst synthesized 18.9% (w/w) FOS (59.1 g/L of neokestose, 30.2 g/L of 1-kestose, 11.6 g/L of neonystose and 12.6 g/L of blastose). The operational stability of PVA-immobilized biocatalyst was assayed in a batch reactor at 30 °C. The enzyme preserved its initial activity during at least 7 cycles of 26 h.

Ref.: N. Miguez, M. Gimeno-Perez, D. Fernandez-Polo, F.V. Cervantes, A.O. Ballesteros, M. Fernandez-Lobato, M.H. Ribeiro, F.J Plou. "Immobilization of the β-fructofuranosidase from Xanthophyllomyces dendrorhous by entrapment in polyvinyl alcohol and its application to neo-fructooligosaccharides production". Catalysts 8(5), 201 (2018). doi:10.3390/catal8050201

A simple system to produce 6-kestose

The β-fructofuranosidase Ffase from the yeast Schwanniomyces occidentalis produces potential prebiotic fructooligosaccharides with health-promoting properties, making it of biotechnological interest. Ffase is one of the highest and more selective known producers of 6-kestose by transfructosylation of sucrose. In this work, production of 6-kestose was simplified by directly using cultures of S. occidentalis and Saccharomyces cerevisiae expressing both the wild-type enzyme and a mutated Ffase variant including the Ser196Leu substitution (Ffase-Leu196). Best results were obtained using yeast cultures supplemented with sucrose and expressing the Ffase-Leu196, which after only 4 h produced ~ 116 g/L of 6-kestose, twice the amount obtained with the corresponding purified enzyme. The Ser196Leu substitution skewed production of 6-kestose and neofructooligosaccharides resulting in an increase of ~ 2.2- and 1.5-fold, respectively. Modeling neokestose and blastose into the Ffase-active site revealed the molecular basis explaining the peculiar specificity of this enzyme.

Ref.: D. Rodrigo-Frutos, D. Piedrabuena, J. Sanz-Aparicio, M. Fernández-Lobato. "Yeast cultures expressing the Ffase from Schwanniomyces occidentalis, a simple system to produce the potential prebiotic sugar 6-kestose". Applied Microbiology and Biotechnology (2018), doi:10.1007/s00253-018-9446-y

Enzymatic fructosylation of hydroxytyrosol: reaction and mechanism

We have investigated the ability of the β-fructofuranosidase pXd-INV from the yeast Xanthophyllomyces dendrorhous to glycosylate the olive biophenol hydroxytyrosol (HT). Two fructosylated derivatives (Fru-HT1 and Fru-HT2) were synthesized.MS and 2D-NMR analyses showed that the major product (Fru-HT1) was fructosylated at the primary OH of HT. The structure of the complexes with the substrates and the product analyzed by crystallography led to the understanding of the molecular determinants regulating the enzymatic mechanism. Product-soaked crystals revealed that the minor derivative (Fru-HT2) was fructosylated at the phenolic p-OH group.  One of the studied mutants (N342Q) was notably more specific for the fructosylation at the phenolic OH than the wild-type.



Reference:“Fructosylation of hydroxytyrosol by the β-fructofuranosidase from Xanthophyllomyces dendrorhous: Insights into the molecular basis of the enzyme specificity”. N. Míguez, M. Ramírez-Escudero, M. Gimeno-Pérez, A. Poveda, J. Jiménez-Barbero, A. O. Ballesteros, M. Fernández-Lobato, J. Sanz-Aparicio* and F. J. Plou* ChemCatChem, http://dx.doi.org/10.1002/cctc.201801171 (2018)

Enzymatic synthesis of a novel pterostilbene alpha-D-glucoside

The synthesis of a novel α-glucosylated derivative of pterostilbene was performed by a transglycosylation reaction using starch as glucosyl donor, catalyzed by cyclodextrin glucanotransferase (CGTase) from Thermoanaerobacter sp. The reaction was carried out in a buffer containing 20% (v/v) DMSO to enhance the solubility of pterostilbene. Due to the formation of several polyglucosylated products with CGTase, the yield of monoglucoside was increased by the treatment with a recombinant amyloglucosidase (STA1) from Saccharomyces cerevisiae (var. diastaticus). The monoglucoside was isolated and characterized by combining ESI-MS and 2D-NMR methods. Pterostilbene α-d-glucopyranoside is a novel compound. Pterostilbene α-d-glucopyranoside was less toxic than pterostilbene for human SH-S5Y5 neurons, MRC5 fibroblasts and HT-29 colon cancer cells, and similar for RAW 264.7 macrophages.

Ref: J.L. González-Alfonso, D. Rodrigo-Frutos, E. Belmonte-Reche, P. Peñalver, A. Poveda, J. Jimenez-Barbero, A.O. Ballesteros, Y. Hirose, J. Polaina, J.C. Morales, M. Fernández-Lobato and F. J. Plou. Enzymatic synthesis of a novel pterostilbene α-glucoside by the combination of cyclodextrin glucanotransferase and amyloglucosidase. Molecules 23(6), 1271 (2018). https://doi.org/10.3390/molecules23061271