Production of isomalto-oligosaccharides using dextransucrase immobilized in alginate fibres

Different strategies to co-immobilize dextransucrase and dextranase onto agarose based supports: Operational stability study

Co-immobilization is a groundbreaking technique for enzymatic catalysis, sometimes strategic, as for dextransucrase and dextranase. In this approach, dextranase hydrolytic action removes the dextran layer that covers dextransucrase reactive groups, improving the immobilization. Another advantage is the synergic effect of the two enzymes towards prebiotic oligosaccharides production. Thus, both enzymes were co-immobilized onto the heterobifunctional support Amino-Epoxy-Glyoxyl-Agarose (AMEG) and the ion exchanger support monoaminoethyl-N-ethyl-agarose (Manae) at pH 5.2 and 10, followed or not by glutaraldehyde treatment. This work is the first attempt to immobilize dextransucrase under alkaline conditions. The immobilized dextransucrase on AMEG support at pH 10 (12.78 ± 0.70 U/g) presents a similar activity of the biocatalyst produced at pH 5.2 (14.95 ± 0.82 U/g). The activity of dextranase immobilized onto Manae was 5-fold higher than the obtained onto AMEG support. However, the operational stability test showed that the biocatalyst produced on AMEG at pH 5.2 kept >60% of both enzyme activities for five batches. The glutaraldehyde treatment was not worthwhile to improve the operational stability of this biocatalyst.

Fermentation properties of isomaltooligosaccharides are affected by human fecal enterotypes

Isomaltooligosaccharides (IMOs) are enzymatically synthesized oligosaccharides that have potential prebiotic effects. Five IMO substrates with 2-16° of polymerization (DP) were studied for their fermentation capacities using human microbiomes in an in vitro batch fermentation model. Eleven fecal slurries belonging to three enterotypes, including the Bacteroides-, Prevotella- and Mixed-type, exhibited different degradation rates for long chain IMOs (DP 7 to 16). In contrast, the degradation rates for short chain IMOs (DP 2 to 6) were not affected by enterotypes. Both 16S rRNA gene sequencing and quantitative PCR demonstrated that, after fermentation, the Bifidobacterium growth with IMOs was primarily detected in the Bacteroides- and Mixed-type (non-Prevotella-type), and to a lesser degree in the Prevotella-type. Interestingly, the Prevotella-type microbiome had higher levels of propionic acid and butyric acid production than non-Prevotella-type microbiome after IMOs fermentation. Moreover, principal coordinate analysis (PCoA) of both denaturing gradient gel electrophoresis (DGGE) profiling and 16S rRNA sequencing data demonstrated that the microbiome community compositions were separately clustered based on IMO chain length, suggesting significant impact of DP on the bacterial community structure. The current results clearly demonstrated that the IMO chain length could modulate the structure and composition of the human colonic microbiome. Different responses to short and long chain IMOs were observed from three human enterotypes, indicating that IMOs may be used as therapeutic substrates for directly altering human colonic bacteria.

Immobilization of Glycoside Hydrolase Families GH1, GH13, and GH70: State of the Art and Perspectives

Glycoside hydrolases (GH) are enzymes capable to hydrolyze the glycosidic bond between two carbohydrates or even between a carbohydrate and a non-carbohydrate moiety. Because of the increasing interest for industrial applications of these enzymes, the immobilization of GH has become an important development in order to improve its activity, stability, as well as the possibility of its reuse in batch reactions and in continuous processes. In this review, we focus on the broad aspects of immobilization of enzymes from the specific GH families. A brief introduction on methods of enzyme immobilization is presented, discussing some advantages and drawbacks of this technology. We then review the state of the art of enzyme immobilization of families GH1, GH13, and GH70, with special attention on the enzymes β-glucosidase, α-amylase, cyclodextrin glycosyltransferase, and dextransucrase. In each case, the immobilization protocols are evaluated considering their positive and negative aspects. Finally, the perspectives on new immobilization methods are briefly presented.

Enzymatic synthesis using immobilized Enterococcus faecalis Esawy dextransucrase and some applied studies

Dextrans enzymatic synthesis by immobilized Enterococcus faecalis Esawy dextransucrase was studied. Different parameters, such as: enzyme protein concentration (EPC), substrate concentration (SC), temperature and reaction time were evaluated. EPC played a fundamental role in controlling dextran molecular size with 0.1% dextran in reaction mixture. Dextran 38,397 and 125,471Da were yielded at EPC 4.78 and 5.78mg, respectively. Proper dextrans (73,378 and 117,521Da) demanded in pharmaceutical applications were achieved at 6% and 12% sucrose concentrations and at 4.78 and 5.78mg EPC, respectively. Optimum temperature for conversion of glucose to dextran was 30°C (73% and 80% at 5.78 and 4.78mg EPC, respectively). Varieties of maltooligosaccharides (MOS) were yielded by synergistic cooperation between sucrose and maltose. Six MOS and three dextrans samples in vitro have prebiotic effect on Lactobacillus casei with degree of variation. Two samples of MOS with different degree of polymerization (DP) and three samples of dextran with different molecular weight (MW) reported different fibrinolytic activity.

Synthesis of Oligosaccharides Derived from Lactulose (OsLu) Using Soluble and Immobilized Aspergillus oryzae β-Galactosidase

β-Galactosidase from Aspergillus oryzae offers a high yield for the synthesis of oligosaccharides derived from lactulose (OsLu) by transgalactosylation. Oligosaccharides with degree of polymerization (DP) ≥ 3 have shown to possess higher in vitro bifidogenic effect than di- and tetrasaccharides. Thus, in this work, an optimization of reaction conditions affecting the specific selectivity of A. oryzae β-galactosidase for synthesis of OsLu has been carried out to enhance OsLu with DP ≥ 3 production. Assays with β-galactosidase immobilized onto a glutaraldehyde–agarose support were also carried out with the aim of making the process cost-effective and industrially viable. Optimal conditions with both soluble and immobilized enzyme for the synthesis of OsLu with DP ≥ 3 were 50 °C, pH 6.5, 450 g/L of lactulose, and 8 U/mL of enzyme, reaching yields of ca. 50% (w/v) of total OsLu and ca. 20% (w/v) of OsLu with DP 3, being 6′-galactosyl-lactulose the major one, after a short reaction time. Selective formation of disaccharides, however, was favored at 60 °C, pH 4.5, 450 g/L of lactulose and 8 U/mL of enzyme. Immobilization increased the enzymatic stability to temperature changes and allowed to reuse the enzyme. We can conclude that the use, under determined optimal conditions, of the A. oryzae β-galactosidase immobilized on a support of glutaraldehyde–agarose constitutes an efficient and cost-effective alternative to the use of soluble β-galactosidases for the synthesis of prebiotic OsLu mixtures.

Immobilization of glucansucrase for the production of gluco-oligosaccharides from Leuconostoc mesenteroides

Glucansucrase from Leuconostoc mesenteroides was immobilized in 1 % (w/v) with sodium alginate to produce oligosaccharides. Glucansucrase gave three activity bands of approx. 240, 178, and 165 kDa after periodic acid-Schiff staining with sucrose. The immobilized enzyme had 40 % activity after ten batch reactions at 30 °C and 75 % activity after a month of storage at 4 °C, which is six times more stable than the free enzyme. Immobilized enzyme was more stable at lower (3.5-4.5) and higher (6.5-7.0) pH ranges and higher temperatures (35-40 °C) compared with the free enzyme. Immobilized and free glucansucrase were employed in the acceptor reaction with maltose and each produced gluco-oligosaccharide ranging from trisaccharides to homologous pentasaccharides.

Will isomalto-oligosaccharides, a well-established functional food in Asia, break through the European and American market? The status of knowledge on these prebiotics

This critical review article presents the current state of knowledge on isomalto-oligosaccharides, some well known functional oligosaccharides in Asia, to evaluate their potential as emergent prebiotics in the American and European functional food market. It includes first a unique inventory of the different families of compounds which have been considered as IMOs and their specific structure. A description has been given of the different production methods including the involved enzymes and their specific activities, the substrates, and the types of IMOs produced. Considering the structural complexity of IMO products, specific characterization methods are described, as well as purification methods which enable the body to get rid of digestible oligosaccharides. Finally, an extensive review of their techno-functional and nutritional properties enables placing IMOs inside the growing prebiotic market. This review is of particular interest considering that IMO commercialization in America and Europe is a topical subject due to the recent submission by Bioneutra Inc. (Canada) of a novel food file to the UK Food Standards Agency, as well as several patents for IMO production.

Enhanced production of exocellular glucansucrase from Leuconostoc dextranicum NRRL B-1146 using response surface method

Statistically-based experimental designs were applied to optimize the fermentation for the production of glucosyltransferase by Leuconostoc dextranicum NRRL B-1146. Eleven medium components were examined for their significance on enzyme production using Plackett-Burman factorial design. Tween 80, sucrose and K2HPO4 significantly improved the enzyme production process. The combined effect of these nutrients on glucansucrase production were studied using a 2 2 full-factorial central composite design, a second-order polynomial was established to identify the relationship between the enzyme output and the three medium components. The optimal concentration of variables for maximum glucansucrase production were Tween 80 (0.55%, v/v); sucrose (5.6%, w/v) and K2HPO4 (1%, w/v). The maximum enzyme activity by predicted model was 6.53 U/ml that was in perfect agreement with the actual experimental value (6.40 U/ml).

Design of immobilised dextransucrase for fluidised bed application

Immobilisation of dextransucrase from Leuconostoc mesenteroides NRRL B-512F in alginate is optimised for applications in a fluidised bed reactor with high concentrated sugar solutions, in order to allow a continuous formation of defined oligosaccharides as prebiotic isomalto-oligosaccharides. Efficient design of fluidised bed immobilised biocatalyst in high density solutions requires particles with elevated density, high effectiveness and both thermal and mechanical stability. Inert silica flour/sand (Mikrosil 300) as supplement turned out to be best suited for increasing the density up to 1400 kg m(-3) of the alginate beads and generating a stable expanded bed without diffusional restrictions. Kinetic investigations demonstrate that low effectiveness of immobilised enzyme due to close association to dextranpolymers (dextran content of enzyme preparation >90%) is compensated by reducing the particle size and/or by decreasing the dextran content. A low dextran content (5%) is sufficient to immobilise and stabilise the enzyme, thus diffusional limitation is reduced essentially while operational stability is maintained. Fluidisation behaviour and bed expansion proved to be appropriate for the intended application. Both calculated and measured expansion coefficients showed good agreement for different conditions.

Synthesis of isomaltooligosaccharides and oligodextrans in a recycle membrane bioreactor by the combined use of dextransucrase and dextranase

A recycle ultrafiltration membrane reactor was used to develop a continuous synthesis process for the production of isomaltooligosaccharides (IMO) from sucrose, using the enzymes dextransucrase and dextranase. A variety of membranes were tested and the parameters affecting reactor stability, productivity, and product molecular weight distribution were investigated. Enzyme inactivation in the reactor was reduced with the use of a non-ionic surfactant but its use had severe adverse effects on the membrane pore size and porosity. During continuous isomaltooligosaccharide synthesis, dextransucrase inactivation was shown to occur as a result of the dextranase activity and it was dependent mainly on the substrate availability in the reactor and the hydrolytic activity of dextranase. Substrate and dextranase concentrations (50-200 mg/mL(-1) and 10-30 U/mL(-1), respectively) affected permeate fluxes, reactor productivity, and product average molecular weight. The oligodextrans and isomaltooligosaccharides formed had molecular weights lower than in batch synthesis reactions but they largely consisted of oligosaccharides with a degree of polymerization (DP) greater than 5, depending on the synthesis conditions. No significant rejection of the sugars formed was shown by the membranes and permeate flux was dependent on tangential flow velocity.

Glucosyltransferases acting on starch or sucrose for the synthesis of oligosaccharides

In this work we review the extraordinary biotechnological potential of two glycosyltransferases, cyclodextrin glucanotransferase and dextransucrase, especially their utility in the synthesis of oligosaccharides. Both enzymes are non-Leloir transferases that require neither co-factors nor activated substrates, as they directly employ the free energy of cleavage of starch and sucrose, respectively. Cyclodextrin glucanotransferase is able to produce cyclodextrins from starch. In the presence of appropriate acceptors (e.g., carbohydrates), this enzyme furnishes oligosaccharides containing α(1[Formula: see text]4) bonds. Thus, we have found that glucose, maltose, and sucrose readily serve as acceptors to form the corresponding [Glc-α(1[Formula: see text]4)]n- oligosaccharides, with the degree of polymerization being controlled by the starch:acceptor ratio. The ability of other sugars and related compounds to act as acceptors is also reviewed. Dextransucrase is a glycansucrase that synthesizes dextran using sucrose as glucosyl donor. The formation of dextrans can be quantitatively replaced with the formation of novel oligosaccharides by adding alternative carbohydrate acceptors to the reaction medium. With the dextransucrase from Leuconostoc mesenteroides B-1299, we have investigated the synthesis of gluco- oligosaccharides containing α(1[Formula: see text]2) bonds using methyl 1-O-α-D-glucopyranoside as the acceptor. These products constitute a class of nondigestible nutraceutical oligosaccharides with prebiotic properties relating to the stabilization and enhancement of gastrointestinal tract flora, and are being increasingly used by the food industry.Key words: glycansucrases, cyclodextrin glucanotransferase, cyclodextrin glucosyltransferase, dextransucrase, acceptor products, gluco-oligosaccharides, malto-oligosaccharides, coupling sugar, nutraceuticals, functional foods, prebiotics.