Book Description

Vast amounts of organic residues (including wheat straw) are produced as a result of agricultural activities. Because of a lignin content, many of these biomasses cannot be effectively used as feedstuffs. Selective white-rot fungi uniquely degrade lignin and, thereby, can increase the value of lignified biomasses as a feedstuff. A number of important issues need to be solves to allow for application of this biotechnology in practice. Among these are the stability of fungal treated biomass during long term storage, the compounds produced during fungal treatment and storage, and acceptance of fungal treated biomass by ruminant animals. The research reported in the present thesis showed that wheat straw treated by the fungi Ceriporiopsis subvermispora or Lentinula edodes could be anaerobically stored, with or without additives, at 20 °C up to 64 days with minor effect on its composition. Both fungi acidified the wheat straw by producing a number of organic acids and soluble sugars which accumulated during the fungal treatment. Accumulation of specific ceriporic acids were observed during the C. subvermispora treatment. No common mycotoxins were found to be produced in the two fungal cultures, indicating that the treated wheat straw was safe for animals to consume, at least from the perspective of the 34 analysed mycotoxins. Storing fungal treated wheat straw at different temperatures showed small but significant differences in hemicellulose and lignin content at higher temperatures, but did not affect fermentability in rumen fluid. A number of metabolites accumulated with increased storage temperatures and time. Preference studies with goats showed that the fungal treated wheat straw was well accepted as part of a grass silage and corn silage based ration. Storage of fungal treated wheat straw at elevated temperatures increased its palatability. By adding wheat bran before fungal treatment, a more rapid colonization by C. subvermispora, but not L. edodes, occurred but did not affect the extent of lignin degradation.