Enzymatic modification of dihydromyricetin by glucosylation and acylation, and its effect on the solubility and antioxidant activity.

Although dihydromyricetin exhibits strong potential for pharmaceutical applications, its limited aqueous solubility, permeability and stability restrict its use. In this work, we have synthesized a series of glucosides and acyl-glucosides of dihydromyricetin that could increase the bioavailability of this molecule. First, the R134A variant of sucrose phosphorylase from catalyzed the formation of three monoglucosides, and the major one was identified as dihydromyricetin 4'--α-D-glucopyranoside (>75% conversion yield).

Strategy for the Enzymatic Acylation of the Apple Flavonoid Phloretin Based on Prior α-Glucosylation.

The acylation of flavonoids serves as a means to alter their physicochemical properties, enhance their stability, and improve their bioactivity. Compared with natural flavonoid glycosides, the acylation of nonglycosylated flavonoids presents greater challenges since they contain fewer reactive sites. In this work, we propose an efficient strategy to solve this problem based on a first α-glucosylation step catalyzed by a sucrose phosphorylase, followed by acylation using a lipase.

Selective Synthesis of Galactooligosaccharides Containing β(1→3) Linkages with β-Galactosidase from (Saphera).

The transglycosylation activity of a novel commercial β-galactosidase from (Saphera) was evaluated. The optimal conditions for the operation of this enzyme, measured with -nitrophenyl-β-d-galactopyranoside, were 40 °C and pH around 6.0.

Deciphering the molecular specificity of phenolic compounds as inhibitors or glycosyl acceptors of β-fructofuranosidase from Xanthophyllomyces dendrorhous.

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).

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.

The glucose isomerase GICA from Caldicoprobacter algeriensis was immobilized by ionic adsorption on polymethacrylate carriers (Sepabeads EC-EA and EC-HA) or covalent attachment to glyoxal agarose. The Sepabeads EC-HA yielded the highest recovery of activity (89%). The optimum temperature and pH of immobilized GICA were 90 °C and 7.

Effect of α-Glucosylation on the Stability, Antioxidant Properties, Toxicity, and Neuroprotective Activity of (-)-Epigallocatechin Gallate.

(-)-Epigallocatechin gallate (EGCG), the predominant catechin (≥50%) in green tea (), displays several bioactive properties but its stability and bioavailability are low. In this work, the properties of two α-glucosyl derivatives of EGCG (3'- and 7-O-α-D-glucopyranoside), obtained by enzymatic synthesis, were assessed. The α-glucosylation enhanced the pH and thermal stability of EGCG.

Optimization of Regioselective α-Glucosylation of Hesperetin Catalyzed by Cyclodextrin Glucanotransferase.

The regioselective α-glucosylation of hesperetin was achieved by a transglycosylation reaction catalyzed by cyclodextrin glucanotransferase (CGTase) from 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--α-d-glucopyranoside).

Lipase-Catalyzed Synthesis of Fatty Acid Esters of Trisaccharides.

Carbohydrate fatty acid esters have a broad spectrum of applications in the food, cosmetic, and pharmaceutical industries. The enzyme-catalyzed acylation is significantly more selective than the chemical process and is carried out at milder conditions. Compared with mono- and disaccharides, the acylation of trisaccharides has been less studied.

Efficient α-Glucosylation of Epigallocatechin Gallate Catalyzed by Cyclodextrin Glucanotransferase from Thermoanaerobacter Species.

The glycosylation of plant polyphenols may modulate their solubility and bioavailability and protect these molecules from oxygen, light degradation, and during gastrointestinal transit. In this work, the synthesis of various α-glucosyl derivatives of (-)-epigallocatechin gallate, the predominant catechin in green tea, was performed in water at 50 °C by a transglycosylation reaction catalyzed by cyclodextrin glycosyltransferase from Thermoanaerobacter sp. The molecular weight of reaction products was determined by high-performance liquid chromatography coupled to mass spectrometry.

Enzymatic Synthesis of a Novel Pterostilbene α-Glucoside by the Combination of Cyclodextrin Glucanotransferase and Amyloglucosidase.

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 sp. The reaction was carried out in a buffer containing 20% (/) 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 var.

Micro-scale procedure for enzyme immobilization screening and operational stability assays.

Objective: A simple and inexpensive methodology, based on the use of micro-centrifuge filter tubes, is proposed for establishing the best enzyme immobilization conditions.

Results: The immobilized biocatalyst is located inside the filter holder during the whole protocol, thus facilitating the incubations, filtrations and washings. This procedure minimizes the amount of enzyme and solid carrier needed, and allows exploring different immobilization parameters (pH, buffer concentration, enzyme/carrier ratio, incubation time, etc.

Galactooligosaccharides formation during enzymatic hydrolysis of lactose: towards a prebiotic-enriched milk.

The formation of galactooligosaccharides (GOS) in skim milk during treatment with several commercial β-galactosidases (Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae) was analysed in detail, at 4 and 40°C. The maximum GOS concentration was obtained at a lactose conversion of approximately 40-50% with B. circulans and A.

Analysis of fermentation selectivity of purified galacto-oligosaccharides by in vitro human faecal fermentation.

The in vitro fermentation of several purified galacto-oligosaccharides (GOS), specifically the trisaccharides 4'-galactosyl-lactose and 6'-galactosyl-lactose and a mixture of the disaccharides 6-galactobiose and allolactose, was carried out. The bifidogenic effect of GOS at 1% (w/v) was studied in a pH-controlled batch culture fermentation system inoculated with healthy adult human faeces. Results were compared with those obtained with a commercial GOS mixture (Bimuno-GOS).

Widening the pH activity profile of a fungal laccase by directed evolution.

Unnatural selection: A fungal laccase was tailored by directed evolution to be active at neutral/alkaline pH. After five generations, the final mutant showed a broader pH profile while retaining 50 to 80 % of its activity at neutral pH.

Detailed analysis of galactooligosaccharides synthesis with β-galactosidase from Aspergillus oryzae.

The synthesis of galactooligosaccharides (GOS) catalyzed by β-galactosidase from Aspergillus oryzae (Enzeco) was studied. Using 400 g/L of lactose and 15 U/mL, maximum GOS yield, measured by HPAEC-PAD, was 26.8% w/w of total carbohydrates, obtained at approximately 70% lactose conversion.

Galacto-oligosaccharide synthesis from lactose solution or skim milk using the β-galactosidase from Bacillus circulans.

The synthesis of galacto-oligosaccharides (GOS) catalyzed by a novel commercial preparation of β-galactosidase from Bacillus circulans (Biolactase) was studied, and the products were characterized by MS and NMR. Using 400 g/L lactose and 1.5 enzyme units per milliliter, the maximum GOS yield, measured by HPAEC-PAD analysis, was 165 g/L (41% w/w of total carbohydrates in the mixture).

Laboratory evolution of high-redox potential laccases.

Thermostable laccases with a high-redox potential have been engineered through a strategy that combines directed evolution with rational approaches. The original laccase signal sequence was replaced by the α-factor prepro-leader, and the corresponding fusion gene was targeted for joint laboratory evolution with the aim of improving kinetics and secretion by Saccharomyces cerevisiae, while retaining high thermostability. After eight rounds of molecular evolution, the total laccase activity was enhanced 34,000-fold culminating in the OB-1 mutant as the last variant of the evolution process, a highly active and stable enzyme in terms of temperature, pH range, and organic cosolvents.