The white rot fungus Irpex lacteus CD2 was incubated on corn stover under solid-state fermentation conditions for different durations, from 5 days up to 120 days.
Lignocellulose component loss,
enzyme production and Fe3+-reducing activity were studied. The average
weight loss ranged from 1.7% to 60.5% during the period of 5-120 days. In contrast to
lignin,
hemicellulose and
cellulose were degraded during the initial time period. After 15 days, 63.0% of
hemicellulose was degraded.
Cellulose was degraded the most during the first 10 days, and 17.2% was degraded after 10 days.
Lignin was significantly degraded and modified, with
acid insoluble
lignin loss being nearly 80% after 60 days. That
weight loss, which was lower than the total component loss, indicated that not all of the lost
lignocellulose was converted to
carbon dioxide and water, which was indicated by the increase in soluble reducing
sugars and
acid soluble
lignin. Filter paper activity, which corresponds to total
cellulase activity, peaked at day 5 and remained at a high level from 40 to 60 days. High
hemicellulase activity appeared after 30 days. No ligninases activity was detected during the incipient stage of
lignin removal and only low
lignin peroxidase activity was detected after 25 days. Apparently, neither of the enzymatic peaks coincided well with the highest amount of component loss. Fe3+-reducing activity could be detected during all the decay periods, which might play an important role in
lignin biodegradation by I. lacteus CD2.