The effect of adding urea, manganese and linoleic acid to wheat straw and wood chips on lignin degradation by fungi and subsequent in vitro rumen degradation

• Manganese stimulated C. subvermispora to degrade more lignin in wheat straw.
• Addition of both manganese and linoleic acid did not have a synergetic effect.
• The effect of manganese and linoleic acid was substrate and fungus dependent.

The aim of this study was optimizing Ceriporiopsis subvermispora and Lentinula edodes pre-treatment of wheat straw and wood chips by adding urea, manganese and linoleic acid. Optimization was defined as more lignin degradation and an increase in in vitro gas production (IVGP), which is a model for rumen degradation, in comparison to fungal treatment without additives. First urea, manganese and linoleic acid were added separately to C. subvermispora or L. edodes treatment of wheat straw and wood chips. Only manganese and linoleic acid addition improved lignin degradation and IVGP compared to the same treatment without additives. Mn (150 μg/g wheat straw) influenced C. subvermispora treatment most. A combination of manganese and linoleic acid was also applied since both act on manganese peroxidase. This combination did indeed increase lignin degradation in wheat straw by C. subvermispora, but IVGP was not changed. None of the additions had a significant effect on the other fungus–substrate combinations tested here.