Fig. 4

Amount of released humic acids during the enzymatic biodegradation of liquefied coal after 1 h and 24 h of the process. A. liquefied coal (pH 4.2) and laccase preparation, B. liquefied coal (pH 3) and laccase preparation, C. liquefied coal (pH 4.2), laccase preparation and 1 mM ABTS, D. liquefied coal (pH 4.2), laccase preparation and 5 mM ABTS, E. liquefied coal (pH 4.2), laccase preparation and 1 mM sinapic acid (SA), F. liquefied coal (pH 4.2), laccase preparation and 5 mM sinapic acid. Each variant had its own control—instead of enzyme sterile water was added. Control values were subjected from sample values