Secretion of a bundle of (1→3)-β-glucan hollow fibrils from protoplasts of callus suspension under a Ca²⁺-rich and acidic stressed condition

A fiber bundle composed of hollow fibrils is secreted from protoplasts of white birch (Betula phatyphylla Sukatcher var. japonica Kan No. 8) leaves callus and the secretion is more efficient in an acidic medium containing high concentration of Ca²⁺. The influence of the Ca²⁺ concentration and pH has been investigated concerning the number of cells secreted. The secreted hollow fibers were very thin. The ¹³C nuclear magnetic resonance spectra indicated that the fibers are composed of linear (1→3)-β-glucan without branches (callose). The potential utilization of such unique callose fibers and their optimized production needs more investigation.