Compositions and properties of microbial residues formed by three single species fungi and mixed strains in cellulose-containing liquid media

摘要

The microbial residues, due to their closely connection with humic substances (HS), aroused our considerable interest. The method of shake-flask in liquid culture was adopt to accumulate them, in which the cellulose served as the sole C source. The microbial suspensions including Trichoderma viride (Tv), Aspergillus niger (An), Penicillium (P) and mixed strains (Ms) were inoculated into the cellulose culture fluid respectively. The incubation was performed for 70 days at a constant temperature of 28 °C. The results showed that different microbial treatments had different effects on the C turnover in the cellulose fluid, among which Ms performed the most effective role in accumulating microbial residue and consuming organic C of cell metabolic product, Tv followed. As compared to cellulose, large amounts of inorganic N in the fluid could be transferred into the organic N components of residue. In the mean time, the proportion of aromatic rings could be increased at the cost of losing O-containing groups. Specifically, the degrees of condensation were enhanced by Tv and An, however their degrees of oxidation were inhibited. On the contrary, the P and Ms treatments had a significant advantage in the oxydative degradation of cellulose. Although some intermediate products (polysaccharides, phenolic compounds, carboxylic groups and syringyl units etc.) of HS could be detected in the microbial residues treated by Tv and An, their organic molecules did not still achieve the polymerization degree of real HS.