A Study of Biodegradation Kinetics of Cellulose and Its Derivatives Using of the Sturm Test

The biodegradation kinetics of such polysaccharide materials as microcrystalline cellulose, hydrated cellulose (viscose fiber), and native starch (reference sample) was studied. The biodegradation kinetics was evaluated by accumulation of carbon dioxide in the course of mineralization of organic substances under the action of soil microbiota (soil inoculum) using the Sturm test. The degrees of biodegradation of powdered fibrous cellulose and hydrated cellulose were found to be similar: 69.2 and 67.0% in 98 days. Microcrystalline cellulose appeared to be resistant to microbiological degradation (2.0% degradation), which is due to high stability of crystalline formations under the action of microbial metabolism products. After the biodegradation experiments, the strongly degrading cellulose samples had numerous structural defects, their color changed, and signs of the development of micromycetes were revealed. The absorption intensity in the regions corresponding to the O–H and C–O vibrations in the IR spectra decreased, which proves the degradation of polysaccharides. On the other hand, the intensity of the N–H vibration bands increased, which suggests accumulation of chitin, the main component of the cell walls of microscopic fungi fixed and sprouted on the sample surface. Biodegradation leads to a decrease in the molecular mass of powdered cellulose and hydrated cellulose samples, which is confirmed by a decrease in the temperature of thermal oxidative degradation.