Optimization of Cultivation Conditions for Azotobacter vinelandii D-08, Producer of the Polysaccharide Levan, for Obtaining Biocomposite Materials

Abstract

A prospective binder composed of a microbial polysaccharide levan present in the culture fluid was obtained. The synthesis of levan was carried out by an Azotobacter vinelandii bacteria strain using molasses, distillery stillage, and milk whey as the nutrient medium. The maximum amount of levan produced in these experiments was 14.5 g/L. Composite materials were obtained based on wood waste and biological binder. Depending on the pressing behaviour, materials were obtained within a density range of 1083 to 1443 kg/m3 and a tensile strength of 7.2 to 32.4 MPa. Water absorption and thickness swelling were 7.2% and 14.9%, respectively. During hot pressing, the resulting materials changed in their attenuated total reflection-frustrated total reflection (ATR-FTR) spectra at frequencies of 930, 1000, and 1750 cm-1, indicating the occurrence of chemical and structural changes in individual components of the lignocellulosic raw materials and changes in the composition of biological binding agent. Analysis of the physico-mechanical properties and other results of the composite materials using scanning electron microscopy (SEM) and X-ray microtomography suggested that composite materials based on the microbial polysaccharide levan-containing binder are advanced, new, and eco-friendly substances.

Keywords

• Levan
• Azotobacter vinelandii D – 08
• Particleboard
• Polysaccharide binders
• Biocomposite material