β-Glucans: Relationships between Modification, Conformation and Functional Activities

Abstract

β-glucan is a type of polysaccharide which widely exists in bacteria, fungi, algae, and plants, and has been well known for its biological activities such as enhancing immunity, antitumor, antibacterial, antiviral, and wound healing activities. The conformation of β-glucan plays a crucial role on its biological activities. Therefore, β-glucans obtained from different sources, while sharing the same basic structures, often show different bioactivities. The basic structure and inter-molecular forces of polysaccharides can be changed by modification, which leads to the conformational transformation in solution that can directly affect bioactivity. In this review, we will first determine different ways to modify β-glucan molecules including physical methods, chemical methods, and biological methods, and then reveal the relationship of the flexible helix form of the molecule chain and the helix conformation to their bioactivities. Last, we summarize the scientific challenges to modifying β-glucan's conformation and functional activity, and discuss its potential future development.

Keywords: conformation transformation; functional activities; modification; β-glucans.

Figure 1

Scheme of possible polysaccharide chain conformations in aqueous solution.

Figure 2

Atomic Force Microscope (AFM) image (a) and schematic representation of the lentinan solution at 25 °C (b). Adapted from [5], with permission from the American Chemical Society, Copyright 2008.

Figure 3

The AFM topology graph of Pleurotus geesteranus β-d-glucan at different magnifications at 4 °C (a) and 22 °C (b) (reproduced from [18] with permission from John Wiley and Sons, Copyright 2009).

Figure 4

Schematic representation of the different types of helical structures of Pleurotus geesteranus β-d-glucan (reproduced from [18] with permission from John Wiley and Sons, Copyright 2009).

Figure 5

Schematic depiction of the interaction between the phosphorylated pachymaran P-PCS3-II chain and receptors on the immune cell (reprinted from Carbohydr. Polym., 78, Chen, X.; Xu, X.; Zhang, L.; Zeng, F., Chain conformation and anti-tumor activities of phosphorylated (1→3)-β-d-glucan from Poria cocos, pp. 581–587, Copyright (2009), with permission from Elsevier [15]).