Structural changes in wheat straw components during decay by lignin‐degrading white‐rot fungi in relation to improvement of digestibility for ruminants

Abstract

Structural changes and resulting in-vitro dry matter digestibility (IVDMD) were determined during the course of solid-state fermentation of wheat straw using the lignin-degrading white-rot fungi Sporotrichum pulverulentum, Pycnoporus cinnabarinus and Cyathus stercoreus. The first fungus grew very rapidly on straw but degraded hemicelluloses and cellulose non-selectively resulting in very low IVDMD increases (50% after 35% weight loss). P. cinnabarinus and C. stercoreus preferentially degraded hemicelluloses achieving high improvements in IVDMD (maximum increase of 63 and 94%, respectively) with limited dry weight losses (12 and 18% after 7 and 13 days, respectively). The three fungi exhibited some selectivity among the individual hemicellulose components: 0-acetyls were removed essentially at the same rate as xylan, while uronic acids accumulated as incubation proceeded. Conversely, the arabinose content decreased rapidly, especially with C. stercoreus and P. cinnabarinus, suggesting that removal of this pentose was partly responsible for digestibility improvement. Esterified phenolic acids were rapidly degraded during the first stages of decay by all three fungi although P. cinnabarinus and C. stercoreus degraded ferulic acid faster than p-coumaric acid. Lignin was preferentially degraded compared to polysaccharides by all three fungi. The amount of lignin removed, as determined by Klason, correlated well with IVDMD improvement (r= -0.97), while acid detergent lignin (ADL) showed a lower correlation (r= -0.86). Acidolysis yields of decayed lignin pointed to preferential degradation of 8 -0 -4 ether linked units by the fungi. Syringyl units were removed faster than guaiacyl units only after 5 to 10% weight loss was obtained.

Avaliação das alterações bromatológicas e de degradabilidade do resíduo de lixadeira do algodão após tratamento biológico com Pleurotus sajor-caju

“…O Pleurotus sajor-caju, como outros fungos causadores da podridão-branca da madeira, mostrou-se eficiente em reduzir as frações FDN e FDA (P < 0,05) e em aumentar o teor de PB (P < 0,05) dos substratos C1 e C2 em relação ao resíduo-testemunha (ZANDRAZIL, 1977;AGOSIN et al, 1985;WOOD e SCHMIT, 1987;AGOSIN et al, 1990;BUSWELL et al, 1996;BISARIA et al, 1996). Schmidt (2002) afirmou que fungos do gênero Pleurotus não incorporam nitrogênio atmosférico; as elevações verificadas no teor de PB dos substratos após tratamentos são relativas e devidas à perda de outros nutrientes.…”

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

“…Chitin is a basic structural component of the fungal cell wall. Fungal mycelial growth and infiltration into the substrate thus increases the chitin content (Agosin et al 1985). Fungal chitin content depends upon the species and growing conditions (Arora and Sharma 2009).…”

“…White-rot fungi are very specific and differ in their capabilities of delignification from one source to another (Tripathi et al 2008). Increases in delignification and digestibility by fungi largely depend on the substrate and fungal strain (Agosin et al 1985;Tuyen et al 2013). Therefore, the present study was carried out to investigate the effects of C. subvermispora, L. edodes, and P. acerina on nutrients losses, chemical composition, and rumen fermentation characteristics of rape straw.…”

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

“…Many fungal species have been screened for their potential to degrade cereal residues. White rot fungi are the most studied and degrade lignin effi ciently by using their ligninolytic enzyme system (Agosin et al, 1985;Arora et al, 2002). Lignin is bound to cellulose and hemicellulose and makes these components inaccessible for microbial attack.…”