DISPERSION OF LIGNIN IN WATER - CHARACTERIZATION OF THE PHENOMENON AND INFLUENCE ON LIGNIN ENZYMATIC DEGRADABILITY

During precipitation of lignin into water from a dimethylformamide (DMF) solution, a fraction of lignin does not sediment and forms a turbid solution. The lignin dispersed in water is called colloidal lignin. The yield of colloidal lignin increases with the final concentration of DMF in water. The whole lignin sample can be converted into the colloidal state with 2% final concentration of DMF in water by successive solubilization/precipitation cycles of the non-colloidal lignin fraction. Compared to precipitated lignin, colloidal lignins do not show significant differences in molecular size distribution and chemical structure, as shown by UV and IR spectra, sugar content and thioacidolysis characterization. The reactivity of colloidal lignins for oxidation by the lignin peroxidase of Phanerochaete chrysosporium is considerably higher that that of native lignins.