β-Glucan fragmentation by microfluidization and TNF-α-immunostimulating activity of fragmented β-glucans

Fragmentation of β-glucans secreted by the fungus Ophiocordyceps dipterigena BCC 2073 achieved by microfluidization was investigated. The degree of β-glucan fragmentation was evaluated based on the average number of chain scissions (α). The effects on the α value of experimental variables like solid concentration of the β-glucan suspension, interaction chamber pressure, and number of passes through the microfluidizer were examined. Kinetic studies were conducted using the relationships of the α and suspension viscosity values with the number of passes. Evidence indicated that α increases with the interaction chamber pressure and the number of passes, whereas the solid concentration shows the inverted effect. Kinetic data indicated that the fragmentation rate increases with β-glucan solid concentration and interaction chamber pressure. Furthermore, since β-glucan molecular weight is a key factor determining its biological activity, the effect of β-glucans of different molecular weights produced by fragmentation on tumor necrosis factor (TNF)-α-stimulating activity in THP-1 human macrophage cells was investigated. Evidence suggested that β-glucans have an immunostimulating effect on macrophage function, in the absence of cytotoxic effects. Indeed, β-glucans characterized by a range of molecular weights produced via microfluidization exhibited promise as immunostimulatory agents.