A convenient preparation of maltooctaose and maltononaose by the coupling reaction of cyclomaltodextrinase

Ring-Opening of Cyclodextrins: An Efficient Route to Pure Maltohexa-, Hepta-, and Octaoses

Many preparations of maltooligosaccharides have been described in literature, essentially using enzymatic or biotechnological processes. These compounds, derived from starch, are well-known as prebiotic agents. The use of maltohexa-, hepta-, and octaoses as synthons in organic synthesis was also well documented in literature. They can indeed be obtained as single compounds by the cyclodextrins’ ring-opening. This reaction has been studied for many years, varying the protecting and functional groups and the reaction conditions, leading to functionalized oligomaltoses. These compounds are of wide interest in various fields. They have a strong potential as scaffolds for multivalence in chemobiology, as building blocks for the production of biomimetic pseudo-glycopeptides, as well as monomers for the preparation of materials. In view of the importance of these oligomaltoses, this review focuses on the different methodologies allowing access to them via chemical and enzymatic ring-opening of cyclodextrins.

One-pot production of maltoheptaose (DP7) from starch by sequential addition of cyclodextrin glucotransferase and cyclomaltodextrinase

Maltodextrins (dextrins) are glucose chains normally produced by starch hydrolysis. Maltodextrins are characterized by their degree of polymerization (DP), which indicates the average number of glucose units per chain. Maltoheptaose (DP7), also known as amyloheptaose, is one of the maltodextrin mixtures widely used in foods, cosmetics, and pharmaceutical industries. Recently, the enzymatic synthesis of DP7 has attracted considerable attention, owing to its considerable advantages over chemical methods. In this work, we have designed a one-pot cascade reaction bio-synthesis starting from soluble starch to produce a specific degree of polymerization (DP7). The reaction system was catalyzed by cyclodextrin glucotransferase (GaCGT) from Gracilibacillus alcaliphilus SK51.001CGTase (transglycosylation/cyclization reaction) and cyclomaltodextrinase (BsCD) from Bacillus sphaericus E-244CDase (ring-opening reaction). The one-pot cascade reaction exhibited an optimum temperature of 30 °C and pH 7.0, and the addition of Ca²⁺ enhanced the maltoheptaose production. The optimum enzyme units for the one-pot cascade reaction were 80 U/g of GaCGT and 1 U/g of BsCD. However, the sequential addition of the enzymes exhibited a 5-fold higher conversion rate over simultaneous addition. The one-pot cascade reaction converted 30 g/L of soluble starch to 5.4 g/L of maltoheptaose in 1 h reaction time with a conversion rate of 16 %.

Biochemical and structural features of a novel cyclodextrinase from cow rumen metagenome

A novel enzyme, RA.04, belonging to the alpha-amylase family was obtained after expression of metagenomic DNA from rumen fluid (Ferrer et al.: Environ. Microbiol. 2005, 7, 1996-2010). The purified RA.04 has a tetrameric structure (280 kDa) and exhibited maximum activity (5000 U/mg protein) at 70 degrees C and was active within an unusually broad pH range from 5.5 to 9.0. It maintained 80% activity at pH 5.0 and 9.5 and 75 degrees C. The enzyme hydrolyzed alpha-D-(1,4) bonds 13-fold faster than alpha-D-(1,6) bonds to yield maltose and glucose as the main products, and it exhibited transglycosylation activity. Its preferred substrates, in the descending order, were maltooligosaccharides (C3-C7), cyclomaltoheptaose (beta-CD), cyclomaltohexaose (alpha-CD), cyclomaltooctaose (gamma-CD), soluble starch, amylose, pullulan and amylopectin. The biochemical properties and amino acid sequence alignments suggested that this enzyme is a cyclomaltodextrinase. However, despite the similarity in the catalytic module (with Glu359 and Asp331 being the catalytic nucleophile and substrate-binding residues, respectively), the enzyme bears a shorter N-terminal domain that may keep the active site more accessible for both starch and pullulan, compared to the other known CDases. Moreover, RA.04 lacks the well-conserved N-terminal Trp responsible for the substrate preference typical of CDases/MAases/PNases, suggesting a new residue is implicated in the preference for cyclic maltooligosaccharides. This study has demonstrated the usefulness of a metagenomic approach to gain novel debranching enzymes, important for the bread/food industries, from microbial environments with a high rate of plant polymer turnover, exemplified by the cow rumen.

Enzymatic preparation of maltohexaose, maltoheptaose, and maltooctaose by the preferential cyclomaltooligosaccharide (cyclodextrin) ring-opening reaction of Pyrococcus furiosus thermostable amylase

Specific-length maltooligosaccharides, particularly maltohexaose, maltoheptaose, and maltooctaose, were prepared from cyclomaltooligosaccharides (cyclodextrins, CDs) by the preferential cyclodextrin ring-opening reaction of an amylolytic enzyme from Pyrococcus furiosus. The enzyme primarily produces maltohexaose, maltoheptaose, and maltooctaose by hydrolyzing alpha-, beta-, and gamma-CD, respectively. This study aims to develop a high-efficiency synthesis of specific maltooligosaccharides at high-purity. [formula: see text]