Fungal pretreatment to improve digestibility of corn stover for animal feed

Lignin reduces the digestibility of corn stover as animal feed. Fungal pretreatment has proven an effective way to degrade lignin to improve the bioavailability of corn stover. To understand further the dynamics of the fungal pretreatment process, we investigated the effects of three key parameters (i.e., cultivation time, culture inoculum dosage, and sterilization) on pretreatment of corn stover using a white-rot fungus (Ceriporiopsis subvermispora). Corn stover was inoculated with different dosages of C. subvermispora culture and cultivated for 10, 20, and 30 days. The digestibility of the pretreated corn stover was evaluated by both enzymatic hydrolysis and in vitro fermentation with rumen fluid. The lignin degradation in corn stover increased from 0.1% to 20.7% between days 10 and 30. Compared to the raw sample, corn stover pretreated with fungi for 30 days had a significantly greater glucose yield (53.8% compared to 23.3%) and xylose yield (37.9% compared to 13.1%) when enzymatic hydrolysis was conducted (p < 0.05). Increasing the culture inoculum dosage from 4 to 16 mL did not affect the digestibility of corn stover (p > 0.05). Fungal-pretreated corn stover had a greater in vitro fermentation rate than raw corn stover during the first 8 h. Fungal pretreatment of non-sterile corn stover caused a substantially reduced sugar yield and in vitro fermentation rate, indicating that sterilization is an important step before fungal pretreatment. The results of this study provide key information for the future development of fungal pretreatment of corn stover.