Composites of bacterial cellulose and alginate produced in situ: The impact of viscosity and temperature on the microscale morphology

Abstract

The scope of this work was to study the impact of viscosity and temperature on the microscale morphology of bacterial cellulose (BC) membranes grown on cultivation media containing sodium alginate (SA). The membranes were successfully produced by stationary cultivation of Gluconacetobacter hansenii at 25 °C and 28 °C in modified Hestrin-Schramm (HS) medium, containing various amounts of added SA. It was shown that cross-linking with Ca²⁺ ions prior to washing was mandatory for alginate retention in the BC matrix. The loading of alginate in resulting composites depended on the SA content in the cultivation medium and reached the saturation value of ca. 40 % at 2 % concentration. The introduction of alginate in the BC membrane interfered with the liquid crystalline-like (LC-like) ordering of fibrils. The helical half-pitch was reduced from 65 μm for SA-free medium to 25–30 μm at the SA concentration of 2 %. For higher SA concentrations in the medium, the portions of membrane with LC-like ordering were strongly reduced, and more pores were formed.