Analysis of Transglucosylation Products of Aspergillus niger α-Glucosidase that Catalyzes the Formation of α-1,2- and α-1,3-Linked Oligosaccharides

Insights into the transglucosylation activity of α-glucosidase from Schwanniomyces occidentalis

The α-glucosidase from Schwanniomyces occidentalis (GAM1p) was expressed in Komagataella phaffii to about 70 mg/L, and its transferase activity studied in detail. Several isomaltooligosaccharides (IMOS) were formed using 200 g/L maltose. The major production of IMOS (81.3 g/L) was obtained when 98% maltose was hydrolysed, of which 34.8 g/L corresponded to isomaltose, 26.9 g/L to isomaltotriose, and 19.6 g/L to panose. The addition of glucose shifted the IMOS synthesis towards products containing exclusively α(1 → 6)-linkages, increasing the production of isomaltose and isomaltotriose about 2-4 fold, enabling the formation of isomaltotetraose, and inhibiting that of panose to about 12 times. In addition, the potential of this enzyme to glycosylate 12 possible hydroxylated acceptors, including eight sugars and four phenolic compounds, was evaluated. Among them, only sucrose, xylose, and piceid (a monoglucosylated derivative of resveratrol) were glucosylated, and the main synthesised products were purified and characterised by MS and NMR. Theanderose, α(1 → 4)-D-glucosyl-xylose, and a mixture of piceid mono- and diglucoside were obtained with sucrose, xylose, and piceid as acceptors, respectively. Maximum production of theanderose reached 81.7 g/L and that of the glucosyl-xylose 26.5 g/L, whereas 3.4 g/L and only 1 g/L were produced of the piceid mono- and diglucoside respectively. KEY POINTS: • Overexpression of a yeast α-glucosidase producing novel molecules. • Yeast enzyme producing the heterooligosaccharides theanderose and glucosyl-xylose. • Glycosylation of the polyphenol piceid by a yeast α-glucosidase.

Structural insights into starch-metabolizing enzymes and their applications

Starch is a polysaccharide produced exclusively through photosynthesis in plants and algae; however, is utilized as an energy source by most organisms, from microorganisms to higher organisms. In mammals and the germinating seeds of plants, starch is metabolized by simple hydrolysis pathways. Moreover, starch metabolic pathways via unique oligosaccharides have been discovered in some bacteria. Each organism has evolved enzymes responsible for starch metabolism that are diverse in their enzymatic properties. This review, focusing on eukaryotic α-glucosidases and bacterial α-glucoside-hydrolyzing enzymes, summarizes the structural aspects of starch-metabolizing enzymes belonging to glycoside hydrolase families 15, 31, and 77 and their application for oligosaccharide production.

Plant polysaccharide degradation-related enzymes in Aspergillus oryzae

Plants synthesize large amounts of stored and structural polysaccharides. Aspergillus oryzae is used in traditional Japanese fermentation and produces many types of plant polysaccharide degradation-related enzymes. The carbohydrate-active enzymes of A. oryzae are important in the fermentation process and biotechnological applications. Because plant polysaccharides have a complex structure, cooperative and synergistic actions of enzymes are crucial for the degradation of plant polysaccharides. For example, the cooperative action of isoprimeverose-producing oligoxyloglucan hydrolase, β-galactosidase, and α-xylosidase is important for the degradation of xyloglucan, and A. oryzae coordinates these enzymes at the expression level. In this review, I focus on the plant polysaccharide degradation-related enzymes identified in A. oryzae.

Biochemical characterization of glycoside hydrolase family 31 α-glucosidases from Myceliophthora thermophila for α-glucooligosaccharide synthesis

The transglucosidase activity of GH31 α-glucosidases is employed to catalyze the synthesis of prebiotic isomaltooligosaccharides (IMOs) using the malt syrup prepared from starch as substrate. Continuous mining for new GH31 α-glucosidases with high stability and efficient transglucosidase activity is critical for enhancing the supply and quality of IMO preparations. In the present study, two α-glucosidases (MT31α1 and MT31α2) from Myceliophthora thermophila were explored for biochemical characterization. The optimum pH and temperature of MT31α1 and MT31α2 were determined to be pH 4.5 and 65 °C, and pH 6.5 and 60 °C, respectively. Both MT31α1 and MT31α2 were shown to be stable in the pH range of 3.0 to 10.0. MT31α1 displayed a high thermostability, retaining 60 % of activity after incubation for 24 h at 55 °C. MT31α1 is highly active on substrates with all types of α-glucosidic linkages. In contrast, MT31α2 showed preference for substrates with α-(1→3) and α-(1→4) linkages. Importantly, MT31α1 was able to synthesize IMOs and the conversion rate of maltose into the main functional IMOs components reached over 40 %. Moreover, MT31α2 synthesizes glucooligosaccharides with (consecutive) α-(1→3) linkages. Taken together, MT31α1 and MT31α2, showing distinct substrate and product specificity, hold clear potential for the synthesis of prebiotic glucooligosaccharides.

A comprehensive review on the properties, production, and applications of functional glucobioses

Glucobiose is a range of disaccharides consisting of two glucose molecules, generally including trehalose, kojibiose, sophorose, nigerose, laminaribiose, maltose, cellobiose, isomaltose, and gentiobiose. The difference glycosidic bonds of two glucose molecules result in the diverse molecular structures, physiochemical properties and physiological functions of these glucobioses. Some glucobioses are abundant in nature but have unconspicuous roles on health like maltose, whereas some rare glucobioses display remarkable biological effects. It is unpractical process to extract these rare glucobioses from natural resources, while biological synthesis is a feasible approach. Recently, the production and application of glucobiose have attracted considerable attention. This review provides a comprehensive overview of glucobioses, including their natural sources and physicochemical properties like structure, sweetness, digestive performance, toxicology, and cariogenicity. Specific enzymes used for the production of various glucobioses and fermentation production processes are summarized. Additionally, their versatile functions and broad applications are also introduced.

Structural characterization of slow digestion dextrin synthesized by a combination of α-glucosidase and cyclodextrin glucosyltransferase and its prebiotic potential on the gut microbiota in vitro

Starch-based dietary fibers are at the forefront of functional ingredient research. In this study, a novel water-soluble slow digestion dextrin (SDD) was synthesized by synergy of α-glucosidase and cyclodextrin glucosyltransferase and characterized. Results showed that SDD exhibited high solubility, low viscosity, and resistance to digestive enzymes, and also showed an increased dietary fiber content of 45.7% compared with that of α-glucosidase catalysis alone. Furthermore, SDD was used as the sole carbon source to ferment selected intestinal strains and human fecal microflora in vitro to investigate its prebiotic effects. It was found that SDD could markedly enriched the abundance of Bifidobacterium, Veillonella, Dialister, and Blautia in human gut microflora and yielded higher total organic acid. The combination of α-glucosidase and cyclodextrin glucosyltransferase in this study showed valuable potential for the preparation of a novel slow digestion dextrin with good physicochemical properties and improved prebiotic effects.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.

The bifidogenic effects and dental plaque deformation of non-digestible isomaltooligosaccharides synthesized by dextransucrase and alternansucrase

Non-digestible isomaltooligosaccharides (NDIMOS) are functional food and beverage ingredients that contributed to human health benefits through metabolism of gastrointestinal microorganism. In this study, NDIMOS were synthesized by combine dextransucrase from Leuconostoc mesenteroides B512F/KM and alternansucrase from L. mesenteroides NRRL 1355CF10/KM using sucrose as substrate and maltose as acceptor. Their digestibility was confirmed by using digestive enzymes including α-amylase and amyloglucosidase. NDIMOS inhibited insoluble glucan formation through mutansucrase from Streptococcus mutans. The bifidogenic effect of NDIMOS was investigated by growth of four strains of Bifidobacterium in MRS broth containing NDIMOS, compared with MRS broth contain glucose and negative control. Additionally, Bifidobacterium bifidum or Bifidobacterium adolescentis inhibited the growth of Salmonella enterica serovar typhimurium when they were co-cultivation in MRS broth containing NDIMOS. These results suggested that NDIMOS is potential functional ingredient for food, beverage, and pharmaceutical application.

Modification of the transglucosylation properties of α-glucosidases from Aspergillus oryzae and Aspergillus sojae via a single critical amino acid replacement

We constructed enzyme variants of the α-glucosidases from Aspergillus oryzae (AoryAgdS) and Aspergillus sojae (AsojAgdL) by mutating the amino acid residue at position 450. AoryAgdS_H450R acquired the ability to produce considerable amounts of α-1,6-transglucosylation products, whereas AsojAgdL_R450H changed to produce more α-1,3- and α-1,4-transglucosylation products than α-1,6-products. The 450th amino acid residue is critical for the transglucosylation of these α-glucosidases.