Towards practical application of fungal-treated lignocellulosic biomass as ruminant feed

Summary

Lignocellulosic biomass represents the most abundant global source of renewable biomass. White-rot fungi can effectively break down lignin in lignocellulosic biomass and, thereby, improve its suitability as a ruminant feed. The general aim of the research described in this thesis was to study a number of challenges associated with practical application of the white-rot fungal biotechnology: selecting optimal fungus-biomass combinations, testing fungal colonized substrates (fresh and preserved) as spawn and investigating conditions to facilitate new storage methods.It is important to screen excellent fungus-biomass combinations before practical application. In Chapter 2, wheat straw, barley straw, oat straw, rapeseed straw, miscanthus, new reed, spent reed, and cocoa shells were treated with Ceriporiopsis subvermispora, Lentinula edodes, and Pleurotus eryngii. Given the unavailability of grain spawn in certain parts of the world, in Chapter 3, C. subvermispora and L. edodes colonized wheat straw was tested as spawn to inoculate new batches of sterile wheat straw. Chapter 4, C. subvermispora and L. edodes colonized wheat straw was anaerobically stored at 20 or 30°C for 2 or 4 weeks, after which the anaerobically stored colonized wheat straw was used to inoculate a new batch of sterile wheat straw. To potentially make the pelleting of fungal-treated wheat straw possible, in Chapter 5, C. subvermispora and L. edodes were inoculated on sterile wheat straw with different moisture contents to determine growth rate in race tubes as well as IVGP and chemical composition in boxes.Biomass with low quality (in terms of rumen fermentability) has a higher net improvement, indicating that low-quality biomass has greater economic potential for conversion to ruminant feed. Both C. subvermispora and L. edodes colonized wheat straw can repeatedly be used to inoculate new batches of wheat straw, with stable improvement in nutritional value as ruminant feed. Anaerobically stored C. subvermispora, unlike L. edodes colonized wheat straw can also be used as spawn for wheat straw, as effective as sorghum spawn. Finally, fungal growth, lignin degradation, and nutritional value improvement are not directly related and their relationships vary with moisture content.