Effect of white rot basidiomycetes on chemical composition and in vitro digestibility of oat straw and alfalfa stems

Abstract

Five white rot basidiomycetes were evaluated for their potential to improve ruminal degradation of oat straw and alfalfa stems. Phanerochaete chrysosporium (PC), Scytinostroma galactinum (SG), Phlebia tremellosa (PT), Phellinus pini (PP), and Pholiota mutabilis (PM) were incubated on oat straw and alfalfa stems for 30 d at 28 degrees C and 90% relative humidity. Detergent fiber and total fiber components (neutral sugars, uronic acids, Klason lignin [KL], and ester- and ether-linked non-core lignin phenolics), core lignin nitrobenzene oxidation products, and IVDMD were determined. Electron microscopy of KMnO4-stained and cellulase/colloidal gold-labeled sections was used to monitor fungal activity. Large losses of DM were noted for all fungal species on both substrates. Lignin (KL and ADL) was removed (P less than .05) from oat straw by PC and PT treatment, but no net loss of lignin was observed for fungal treatment of alfalfa stems. Cell-wall polysaccharides were removed from both substrates by fungal activity. Only PC increased (P less than .05) IVDMD of oat straw, and SG, PT, PP, and PC treatment decreased (P less than .05) IVDMD of alfalfa stems, presumably because the fungi removed the most readily fermentable polysaccharides. Transmission electron microscopy using KMnO4 staining showed a nonselective white rot attack. Cytochemical studies using colloidal gold-labeled exo- and endocellulases were used to map the location of cellulose in the cell wall before and after decay by the white rot fungi. All the white rot fungi tested had eroded and thinned cell walls. Residual cell walls were well-labeled; both endo- and exocellulose-colloidal gold identified the cellulosic wall material that remained.(ABSTRACT TRUNCATED AT 250 WORDS)

Variety effect on composition, kinetics of fermentation and <i>in vitro</i> digestibility of oat (<i>Avena sativa</i> L.) straw and its neutral detergent fibre

“…The IVOMD ranged from 400 to 539 g/kg DM. The in vitro DM digestibility of oat straws (from 397 to 529 g/kg DM) was similar to the values reported by Lopez et al (2005) and higher than the values reported by Brown & Almodares (1976) and Jung et al (1992). Differences in the digestibility of straws from different varieties may be due, not only to the chemical composition (Dias-da-silva & Guedes, 1990) but also to stem, leaf and seed ratios (Bhargava et al, 1988).…”

Effect of Fungal Treatments of Rape Straw on Chemical Composition and in vitro Rumen Fermentation Characteristics

“…Inhibition of IVDMD with fungal treatment has also been previously reported, but the mechanism of inhibition is not understood (Jung et al 1992;Karunanandaa and Varga 1996). One possible explanation may be due to the chitin remaining in rape straw after incubation with fungi.…”

Comparative ligninolytic potential of <i>Phlebia</i> species and their role in improvement of <i>in vitro</i> digestibility of wheat straw

“…The loss of these components from the feed is not economically desirable because less biomass is available for animal feed. In an earlier study Phanerocheate chrysosporium, a common and widely studied fungus, degraded lignin but also caused a high loss in total organic matter (TOM) (Jung et al, 1992). To overcome this problem, selective ligninolysis needs to be carried out.…”

“…However, loss of total organic matter is very high during the degradation of lignocellulosics, which limits its practical use and necessitates looking towards selective ligninolytic organisms (Jung et al, 1992). Phlebia species are known selective lignin degraders (Arora and Gill, 2000) and thus may possess the potential capability for improvement of digestibility of agro-residues.…”