Efficient biotransformation and synergetic mechanism of dual-enzyme cascade reaction in nonreducing maltoheptaose synthesis

Permeabilized whole cells containing co-expressed cyclomaltodextrinase and maltooligosyltrehalose synthase facilitate the synthesis of nonreducing maltoheptaose (N-G7) from β-cyclodextrin

BACKGROUND

Maltodextrin is an important bulk ingredient in food and other industries; however, drawbacks such as uneven polymerization and high reducibility limit its utilization. Nonreducing maltoheptaose (N-G7) is a good substitute for maltodextrin owing to its single degree of polymerization and its nonreducing properties. In this study, in vitro cell factory biotransformation of β-cyclodextrin (β-CD) to N-G7 is demonstrated using coexpressed cyclomaltodextrinase (CDase, EC 3.2.1.54) and maltooligosyltrehalose synthase (MTSase, EC 5.4.99.15). However, the cell membrane prevents β-CD from entering the cell owing to its large diameter.

RESULTS

The amylase-deficient permeabilized host ΔycjM-ΔmalS-ΔlpxM is utilized for the coexpression of recombinant CDase and MTSase. Deletion of lpxM effectively allows the entry of β-cyclodextrin into the cell, despite its large diameter, without requiring any relevant cell membrane permeability-promoting reagent. This results in a 28.44% increase in the efficiency of β-CD entry into the cell, thus enabling intracellular N-G7 synthesis without the extracellular secretion of recombinant CDase and MTSase. After reacting for 5.5 h, the highest purity of N-G7 (65.50%) is obtained. However, hydrolysis decreases the purity of N-G7 to 49.30%, thus resulting in a conversion rate of 40.16% for N-G7 when the reaction lasts 6 h. Precise control of reaction time is crucial for obtaining high-purity N-G7.

CONCLUSION

Whole-cell catalysis avoids cell fragmentation and facilitates the creation of an eco-friendly, energy-efficient biotransformation system; thus, it is a promising approach for N-G7 synthesis. © 2023 Society of Chemical Industry.

Physicochemical properties of a non-reducing maltoheptaose prepared by dual-enzyme cascade reaction from starch

The existence of a reducing end in the structure of maltodextrin can limit its applications as undesirable Maillard reaction would occur in some food processing steps. Consequently, a non-reducing maltoheptaose (N-G7) with a single degree of polymerisation was prepared through a cascade reaction of cyclodextrinase and maltooligosyltrehalose synthase, using β-cyclodextrin as substrate. The physicochemical properties of N-G7 were investigated. N-G7 exhibited low moisture absorption ability (8.91 and 18.02% at 43 and 81% relative humidity, respectively), excellent pH stability and thermostability (less than 10% N-G7 was hydrolysed between pH 4 and 10, even at 100°C), and a melting point higher than that of maltodextrin, as well as a typical gel-like behaviour. Most importantly, the results of Maillard reaction indicated that N-G7 was considered to be non-reducing, which suggested that it could be used in food processing where Maillard reaction should be avoided. Overall, the present work may provide important implications for the development and application of N-G7 in food products.

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.