Synergistic action of novel maltohexaose-forming amylase and branching enzyme improves the enzymatic conversion of starch to specific maltooligosaccharide

• Published in: Carbohydrate polymers Vol. 347; p. 122753
• Main Authors: Zhong, Lingli, Wang, Peiwen, Jiang, Min, Zheng, Yitong, Xu, Xiaofan, Ye, Xianfeng, Huang, Yan, Ji, Yanling, Cui, Zhongli, Li, Zhoukun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2025
• Subjects: Asynchronous conversion; Corn starch; Glucan branching enzyme; Maltohexaose-forming amylase; Maltooligosaccharides; Glucan branching enzyme; Asynchronous conversion; Maltooligosaccharides; Corn starch; Maltohexaose-forming amylase
• ISSN: 0144-8617; 1879-1344; 1879-1344
• DOI: 10.1016/j.carbpol.2024.122753

As attractive functional ingredients, maltooligosaccharides (MOS) are typically prepared by controlled enzymatic hydrolysis of starch. However, the random attack mode of amylase often leads to discrete product distribution, thereby reducing yields and purities. In this study, a novel glycoside hydrolase family 13 amylase AmyEs from marine myxobacteria Enhygromyxa salina was identified efficient maltohexaose (G6)-forming ability (40 %, w/w). By deciphering external chain length, we found that the high density of α-1,6-branching points benefits the G6 formation of AmyEs with high purity (71–82 %), indicating the substrate selectivity of AmyEs toward high-branched starch. Based on this, asynchronous conversion strategy was designed to enhance specific MOS yield from corn starch by exploiting branching enzymes and AmyEs, and the purity and yield of G6 respectively increased by 9.5 % and 5 % compared to single AmyEs treatment. Our results demonstrate that combinatorial catalysis of MOS-forming amylases and branching enzymes provides a favorable industrial preparation of specific MOS. The established asynchronous conversion strategy to improve the purity and yield of specific MOS is divided into the following two steps. The first step is to modify starch through glucan branching enzymes, which enhances the content of starch short outer chains and decreases its long inner chain length with high α-1,6-glycosidic bond density. The modification of starch markedly increases the specific exo-cleavage points in starch instead of random endo-cleavage points, which is favorable for product specific. Thus, in the second step, specific MFAses, such as G5-, G6- or G7-amylase, convert the modified starch into high purity MOS with different DP (like G5, G6 or G7) and dextran with special molecular structures. The schematic diagram does not aim to represent the natural conformation of starch. [Display omitted]