Sorption capacity of chitin-glucan complex obtained from industrial waste <i>Aspergillus niger</i>
The introduction specifies the mechanisms of metal accumulation by the fungal biomass, the relevance of using the waste microbiological synthesis of citric acid - biomass of the mycelium <i>Aspergillus niger</i> fungus grown during deep cultivation on beet molasses as a promising source of chitin-glucan complex, which is economically and environmentally sound. The main part of the work presents the results on the sorption capacity of the chitin-glucan complex, isolated during the sequential acid-base hydrolysis from <i>Aspergillus niger</i> biomass. For isolation of purified chitin-glucan complex it is required a certain sequence of treatments with solutions of sodium hydroxide, hydrochloric acid and hydrogen peroxide. The use of harsh thermal and chemical treatment for the treatment of biomass contributes to the removal of proteins, melanoids, and minerals which presence in chitin-glucan complex is undesirable. For the characteristics and comparative analysis of the sorption capacity of the obtained samples of the chitin-glucan complex, the following indicators are used: adsorption activity (sorption capacity), distribution coefficient, and specific surface. The conclusion shows that the sorption capacity of chitin-glucan complex largely depends on both the moisture level of the biomass and the number of stages of acid-base hydrolysis. In the obtained samples of chitin-glucan complex, dried at + 20 °C, with a decrease in humidity, a noticeable decrease in the sorption capacity is observed. A three-stage scheme for the isolation of chitin-glucan complex with an additional depigmentation stage contributes to its complete whitening and a significant increase in its adsorption activity. Chitin-glucan complex is characterized by high sorption capacity with respect to metals. The investigated metal ions, according to the degree of absorption R, form the Co<sup>2+</sup> > Ni<sup>2+</sup> > Mn<sup>2+</sup> > Zn<sup>2+</sup> > Cu<sup>2+</sup> series.