Degradation of a Lignin–Carbohydrate Substrate by Soil Fungi Producing Laccase and Cellobiose Dehydrogenase

The growth of nonsporulating mycelial fungi INBI 2-26(+), a producer of laccase; INBI 2-26(–), a producer of cellobiose dehydrogenase; and their mixed culture on lignin–carbohydrate substrates under conditions of submerged fermentation was studied. The degrees of degradation of lignin, cellulose, and hemicellulose of cut straw over 23 days amounted to 29.8, 51.4, and 72% for the laccase producer; 15.8, 33.9, and 59.1% for the cellobiose dehydrogenase producer; and 15.8, 39.4, and 64.5% for the mixed culture, respectively. The laccase activity in the medium when strain 2-26(+) was cultivated individually reached its maximum on day 28; the activity of cellobiose dehydrogenase of strain 2-26(–), on days 14–28. A method for determining cellobiose dehydrogenase activity in the presence of laccase was developed. In the mixed culture, both enzymes were formed; however, the level of laccase synthesis was 1.5-fold lower compared to that of strain 2-26(+), while synthesis of cellobiose dehydrogenase was similar to that of the corresponding producer. Cellobiose dehydrogenase failed to boost the action of laccase while degrading the lignin of straw.