Preparation of malto-oligosaccharides with specific degree of polymerization by a novel cyclodextrinase from Palaeococcus pacificus

Progress in cyclodextrins as important molecules regulating catalytic processes of glycoside hydrolases

Cyclodextrins (CDs) are important starch derivatives and commonly comprise α-, β-, and γ-CDs. Their hydrophilic surface and hydrophobic inner cavity enable regulation of enzyme catalysis through direct or indirect interactions. Clarifying interactions between CDs and enzyme is of great value for enzyme screening, mechanism exploration, regulation of catalysis, and applications. We summarize the interactions between CDs and glycoside hydrolases (GHs) according to two aspects: 1) CD as products, substrates, inhibitors and activators of enzymes, directly affecting the reaction process; 2) CDs indirectly affecting the enzymatic reaction by solubilizing substrates, relieving substrate/product inhibition, increasing recombinant enzyme production and storage stability, isolating and purifying enzymes, and serving as ligands in crystal structure to identify functional amino acid residues. Additionally, CD enzyme mimetics are developed and used as catalysts in traditional artificial enzymes as well as nanozymes, making the application of CDs no longer limited to GHs. This review concerns the regulation of GHs catalysis by CDs, and gives insights into research on interactions between enzymes and ligands.

N1019D Mutant of Limosilactobacillus reuteri 121 4,6-α-Glucanotransferase GtfB Significantly Improved Catalytic Activity

Limosilactobacillus reuteri 121 4,6-α-glucanotransferase GtfB (Lr 121 GtfB), belonging to glycoside hydrolase family 70 (GH70), synthesizes linear isomalto/malto polysaccharides having (α1→6) linkages attached to the nonreducing ends of (α1→4) linked maltose oligosaccharide segments using starch or maltodextrin as a substrate. Since Lr 121 GtfB has low catalytic activity and efficiency, it leads to substrate regeneration and reduced substrate utilization. In this study, we superimposed the crystal structure of Lr 121 GtfB-ΔNΔV with that of L. reuteri NCC 2613 GtfB-ΔNΔV (Lr 2613 GtfB-ΔNΔV) to identify the acceptor binding subsites +1 to +3 and constructed five single-residue mutants and a random mutagenesis of N1019. Compared with the wild-type, N1019D Lr 121 GtfB-ΔN did not alter the product specificity, increased the catalytic activity and efficiency by 420 and 590%, respectively, and maintained >80% relative activity in the pH 3.5-6.5 interval. The findings will contribute to the industrial application of Lr 121 GtfB and provide new solutions for starch synthesis of higher value derivatives.

Analysis of the action pattern of sequential α-amylases from B. stearothermophilus and B. amyloliquefaciens on highly concentrated soluble starch

Hydrolysis of highly concentrated soluble starch (60%, w/w) was performed using sequential α-amylases from Bacillus stearothermophilus (T, 0.2%, w/w) and Bacillus amyloliquefaciens (B, 0.1%, w/w) to identify their possible action patterns. We found that T reduced the average molecular weight (Mw) of soluble starch from 52,827 Da to 31,914 Da and significantly affected its branched chain length. Compared with soluble starch, the chains with DP 6-12 and DP ≥ 13 in the T samples were diminished by 46% and 96%, respectively. This resulted in an attenuation in the proportions of exterior and inner chains, as well as low iodine binding capacity of the hydrolysates. In contrast, a slower decrease in the average Mw of soluble starch occurred after TB incubation, and the level of DP 6-12 further lowered, causing a gradual decline in the iodine binding capacity of the hydrolysates. Gathered data revealed an unusual action pattern of sequential α-amylase treatment at high substrate concentrations. Bacillus stearothermophilus α-amylase exhibited more pronounced endo-hydrolysis of amylopectin, whereas the attack of Bacillus amyloliquefaciens α-amylase on the exterior chains was enhanced in amylopectin residues. These findings suggest that the synergy of various α-amylases is an effective strategy to promote the dextrinization of highly concentrated starch and finely modify the molecular structure of starch.

Cost-effective and controllable synthesis of isomalto/malto-polysaccharides from β-cyclodextrin by combined action of cyclodextrinase and 4,6-α-glucanotransferase GtfB

Isomalto/malto-polysaccharides (IMMPs) derived from malto-oligosaccharides such as maltoheptaose (G7) are elongated non-branched gluco-oligosaccharides produced by 4,6-α-glucanotransferase (GtfB). However, G7 is expensive and cumbersome to produce commercially. In this study, a cost-effective enzymatic process for IMMPs synthesis is developed that utilizes the combined action of cyclodextrinase from Palaeococcus pacificus (PpCD) and GtfB-ΔN from Limosilactobacillus reuteri 121 to convert β-cyclodextrin into IMMPs with a maximum yield (16.19 %, w/w). The purified IMMPs synthesized by simultaneous or sequential treatments, designated as IMMP-Sim and IMMP-Seq, possess relatively high contents of α-(1 → 6) glucosidic linkages. By controlling the release of G7 and smaller malto-oligosaccharides by PpCD, IMMP-Seq was obtained of DP varying from 12.9 to 29.5. Enzymatic fingerprinting revealed different linkage-type distribution of α-(1 → 6) linked segments with α-(1 → 4) segments embedded at the reducing end and middle part. The proportion of α-(1 → 6) segments containing the non-reducing end was 56.76 % for IMMP-Sim but 28.98 % for IMMP-Seq. Addition of G3 or G4 as specific acceptors resulted in IMMPs exhibiting low polydispersity. This procedure can be applied as a novel bioprocess that does not require costy high-purity malto-oligosaccharides and with control of the average DP of IMMPs by adjusting the substrate composition.

Designing starch derivatives with desired structures and functional properties via rearrangements of glycosidic linkages by starch-active transglycosylases

Modification of starch by transglycosylases from glycoside hydrolase families has attracted much attention recently; these enzymes can produce starch derivatives with novel properties, i.e. processability and functionality, employing highly efficient and safe methods. Starch-active transglycosylases cleave starches and transfer linear fragments to acceptors introducing α-1,4 and/or linear/branched α-1,6 glucosidic linkages, resulting in starch derivatives with excellent properties such as complexing and resistance to digestion characteristics, and also may be endowed with new properties such as thermo-reversible gel formation. This review summarizes the effects of variations in glycosidic linkage composition on structure and properties of modified starches. Starch-active transglycosylases are classified into 4 groups that form compounds: (1) in cyclic with α-1,4 glucosidic linkages, (2) with linear chains of α-1,4 glucosidic linkages, (3) with branched α-1,6 glucosidic linkages, and (4) with linear chains of α-1,6 glucosidic linkages. We discuss potential processability and functionality of starch derivatives with different linkage combinations and structures. The changes in properties caused by rearrangements of glycosidic linkages provide guidance for design of starch derivatives with desired structures and properties, which promotes the development of new starch products and starch processing for the food industry.

Malto-oligosaccharides as critical functional ingredient: a review of their properties, preparation, and versatile applications

Malto-oligosaccharides (MOS) are α-1,4 glycosidic linked linear oligosaccharides of glucose, which have a diverse range of functional applications in the food, pharmaceutical, and other industries. They can be used to modify the physicochemical properties of foods thereby improving their quality attributes, or they can be included as prebiotics to improve their nutritional attributes. The degree of polymerization of MOS can be controlled by using specific enzymes, which means their functionality can be tuned for specific applications. In this article, we review the chemical structure, physicochemical properties, preparation, and functional applications of MOS in the food, health care, and other industries. Besides, we offer an overview for this saccharide from the perspective of prospect functional ingredient, which we feel lacks in the current literature. MOS could be expected to provide a novel promising substitute for functional oligosaccharides.

Maltooligosaccharide forming amylases and their applications in food and pharma industry

Oligosaccharides are low molecular weight carbohydrates with a wide range of health benefits due to their excellent bio-preservative and prebiotic properties. The popularity of functional oligosaccharides among modern consumers has resulted in impressive market demand. Organoleptic and prebiotic properties of starch-derived oligosaccharides are advantageous to food quality and health. The extensive health benefits of oligosaccharides offered their applications in the food, pharmaceuticals, and cosmetic industry. Maltooligosaccharides and isomaltooligosaccharides comprise 2-10 glucose units linked by α-1-4 and α-1-6 glycoside bonds, respectively. Conventional biocatalyst-based oligosaccharides processes are often multi-steps, consisting of starch gelatinization, hydrolysis and transglycosylation. With higher production costs and processing times, the current demand cannot meet on a large-scale production. As a result, innovative and efficient production technology for oligosaccharides synthesis holds paramount importance. Malto-oligosaccharide forming amylase (EC 3.2.1.133) is one of the key enzymes with a dual catalytic function used to produce oligosaccharides. Interestingly, Malto-oligosaccharide forming amylase catalyzes glycosidic bond for its transglycosylation to its inheritance hydrolysis and alternative biocatalyst to the multistep technology. Genetic engineering and reaction optimization enhances the production of oligosaccharides. The development of innovative and cost-effective technologies at competitive prices becomes a national priority.

Molecular Mechanism of Mature Honey Formation by GC-MS- and LC-MS-Based Metabolomics

Honey maturity is an important factor in evaluating the quality of honey; however, there are few studies on the molecular mechanism of the formation of mature honey (MH). In this study, the different metabolites of stomach honey (SH), immature honey (IMH), and MH samples during the same rapeseed flower season were analyzed by an UPLC-QTOF-MS-based metabolomics approach. MH was found to have a distinct metabolic profile to IMH, and a total of 9 different metabolites were obtained, 3 of which, including decenedioic acid, were accumulated in MH. Decenedioic acid as a bee-originated fatty acid (FA) was further verified in rape, acacia, and jujube honey by GC-MS, making it a potential marker to discriminate IMH and MH (P < 0.01). Besides, MH showed higher FAs concentrations; in particular, 3 FAs were significantly richer in MH than IMH (P < 0.05). This study reveals the molecular mechanism from IMH to MH from a FA perspective.

Synergetic modification of waxy maize starch by dual-enzyme to lower the in vitro digestibility through modulating molecular structure and malto-oligosaccharide content

Cyclodextrinase (CDase) and cyclodextrin glucosyltransferase (CGTase) were synergistically used to provide a novel enzymatic method in lowing in vitro digestibility of waxy maize starch. The molecular structure, malto-oligosaccharide composition, and digestibility properties of the generated products were investigated. The molecular weight was reduced to 0.3 × 10⁵ g/mol and 0.2 × 10⁵ g/mol by simultaneous and sequential treatment with CDase and CGTase, while the highest proportion of chains with degree of polymerization (DP) < 13 was obtained by simultaneous treatment. The resistant starch contents were increased to 27.5% and 36.9% by simultaneous and sequential treatments respectively. Dual-enzyme treatment significantly promoted the content of malto-oligosaccharides (MOSs) by hydrolyzing cyclodextrins from CGTase with CDase. However, the replacement of cyclodextrins by MOSs did not obviously influence the digestibility of the products. The starch digestion kinetics further revealed the hydrolysis pattern of these two enzymes on the starch hydrolysate. It was proved that the starch digestibility could be lowered by modulating the molecular structure and beneficial MOSs content by this dual-enzyme treatment.

Biomass-degrading glycoside hydrolases of archaeal origin

During the last decades, the impact of hyperthermophiles and their enzymes has been intensively investigated for implementation in various high-temperature biotechnological processes. Biocatalysts of hyperthermophiles have proven to show extremely high thermo-activities and thermo-stabilities and are identified as suitable candidates for numerous industrial processes with harsh conditions, including the process of an efficient plant biomass pretreatment and conversion. Already-characterized archaea-originated glycoside hydrolases (GHs) have shown highly impressive features and numerous enzyme characterizations indicated that these biocatalysts show maximum activities at a higher temperature range compared to bacterial ones. However, compared to bacterial biomass-degrading enzymes, the number of characterized archaeal ones remains low. To discover new promising archaeal GH candidates, it is necessary to study in detail the microbiology and enzymology of extremely high-temperature habitats, ranging from terrestrial to marine hydrothermal systems. State-of-the art technologies such as sequencing of genomes and metagenomes and automated binning of genomes out of metagenomes, combined with classical microbiological culture-dependent approaches, have been successfully performed to detect novel promising biomass-degrading hyperthermozymes. In this review, we will focus on the detection, characterization and similarities of archaeal GHs and their unique characteristics. The potential of hyperthermozymes and their impact on high-temperature industrial applications have not yet been exhausted.

Cyclodextrinase from Thermococcus sp expressed in Bacillus subtilis and its application in the preparation of maltoheptaose

Background

Maltoheptaose as malto-oligosaccharides with specific degree of polymerization, has wide applications in food, medicine and cosmetics industries. Currently, cyclodextrinase have been applied as prepared enzyme to prepare maltoheptaose. However, the yield and proportion of maltoheptaose was lower, which is due to limited substrate and product specificity of cyclodextrinase (CDase). To achieve higher maltoheptaose yield, cyclodextrinase with high substrate and product specificity should be obtained.

Results

In this study, cyclodextrinase derived from Thermococcus sp B1001 (TsCDase) was successfully expressed and characterized in Bacillus subtilis for the first time. The specific activity of TsCDase was 637.95 U/mg under optimal conditions of 90 °C and pH 5.5, which exhibited high substrate specificity for cyclodextrins (CDs). When the concentration of β-CD was 8%, the yield of maltoheptaose achieved by TsCDase was 82.33% across all reaction products, which exceeded the yields of maltoheptaose in other recent reports. Among malto-oligosaccharides generated as reaction products, maltoheptaose was present in the highest proportion, about 94.55%.

Conclusions

This study provides high substrate and product specificity of TsCDase. TsCDase is able to prepare higher yield of maltoheptaose through conversion of β-CD in the food industry.

Thermophilic 4-α-Glucanotransferase from Thermoproteus Uzoniensis Retards the Long-Term Retrogradation but Maintains the Short-Term Gelation Strength of Tapioca Starch

Gelation of starch is a process during short-term retrogradation. However, long-term retrogradation always leads to the quality deterioration of starch-based food. In this work, a new type of modified tapioca starch (MTS) gel with maintained short-term gelation strength and retarded long-term retrogradation was prepared using a novel recombinantly produced and characterized 4-α-glucanotransferase (TuαGT). In the resulting MTS, the exterior chains of the amylopectin part were elongated and the content of amylose was reduced because of the disproportionation activity of TuαGT. The retrogradation analysis demonstrated that the MTS possessed highly weakened long-term retrogradation characteristics as compared to the native starch. Most importantly, the strength of the gel formed by regelatinized MTS is very close to that of gelatinized native tapioca starch when storing below 30 °C. These findings provide a starting point for developing a novel method for the enzymatic modification of the starch-based gels.

A Cyclodextrin-Based Controlled Release System in the Simulation of In Vitro Small Intestine

A novel cyclodextrin (CD)-based controlled release system was developed in the small intestine to control the rate of drug release, on the premise of enteric-coated tablets. The system was designed based on the enzymes exogenous β-cyclodextrin glycosyltransferase (β-CGTase) and endogenous maltase-glucoamylase (MG), wherein MG is secreted in the small intestine and substituted by a congenerous amyloglucosidase (AG). The vanillin-/curcumin-β-CD complexes were prepared and detected by Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), and host CD degradation was measured based on the glucose yield. The combination of β-CGTase and AG was also functional in the CD complex system. The variations in the concentrations of added β-CGTase, with AG constantly in excess, could effectively alter the rate of host CD degradation and guest release by monitoring glucose production and color disappearance, thus, demonstrating that guest release in the CD complex system could be precisely controlled by changing the amount of β-CGTase used. Thus, the in vitro simulation of the system indicated that a novel controlled release system, based on endogenous MG, could be established in the small intestine. The CD-based controlled release system can be potentially applied in drug delivery and absorption in the small intestine.

Application of cyclodextrinase in non-complexant production of γ-cyclodextrin

The production of γ-cyclodextrin usually includes the utilization of organic complexants. However, the non-complexant production of γ-cyclodextrin is always being explored due to the defects of organic complexants. However, in non-complexant production, the separation of γ-cyclodextrin from α- and β-cyclodextrin is still a challenge. Here, the selective hydrolysis ability of a cyclodextrinase designated PpCD (cyclodextrinase from Palaeococcus pacificus) on α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin was proved. The k_cat /K_m values of PpCD for α-cyclodextrin and β-cyclodextrin were roughly 12-fold and 5-fold higher than that of γ-cyclodextrin. It was proved that PpCD had selective hydrolysis ability and its γ-cyclodextrin purification performance was apparent on various simulated cyclodextrin mixtures with reported proportions derived from different CGTases. Besides, the hydrolysis temperature was optimized and it could be seen that 85°C was appropriate for the production of γ-cyclodextrin. In addition, the production of γ-cyclodextrin was achieved by using PpCD in the γ-CGTase reaction products.