3-97: Biological pretreatments of corn stover with filamentous fungi

Filamentous fungi have been used in the biotechnology industry for several years to produce enzymes.  Fungi producing cellulose-degrading and lignin-degrading enzymes can be grown directly on lignocellulosic biomass in solid state fermentation to break lignin bonds and produce glucose from cellulose. The costs involved in enzyme extraction and application can be eliminated through this process.  However, some dry matter loss will be observed due to aerobic conditions, which can aggravate further if the treatment is performed in unsterile conditions. To limit the dry matter loss, anaerobic conditions can be introduced through ensilage of biomass. Ensilage enables lactic acid bacteria to produce organic acids and lower the pH to 4.0. The low pH and anaerobic conditions minimize microbial activity, thereby decreasing dry matter loss.  In the present research, laccase-producing Pluerotus ostreatus and cellulase-producing Trichoderma reesei were grown on corn stover prior to a 10-day ensilage treatment. Dry matter losses of 1.27% +/- 0.13 and 2.56% +/- 0.49 were observed after 7 and 14 days of fungal growth, respectively. The control samples which had no fungal inocula showed dry matter losses of 1.4% +/- 0.07 and 2.26% +/- 0.06 for the same time periods. The pH values of the samples ranged between 4.2 +/- 0.02 and 4.75 +/- 0.03 for 7 and 14 days. The combined fungal treatment resulted in significant sugar production and lignin degradation.