Abstract
BackgroundThe present work investigated the influence of lignin content and composition in the fungal treatment of lignocellulosic biomass in order to improve rumen degradability. Wheat straw and wood chips, differing in lignin composition, were treated with Lentinula edodes for 0, 2, 4, 8 and 12 wk and the changes occurring during fungal degradation were analyzed using pyrolysis-gas chromatography-mass spectrometry and detergent fiber analysis.ResultsL. edodes preferentially degraded lignin, with only limited cellulose degradation, in wheat straw and wood chips, leaving a substrate enriched in cellulose. Syringyl (S)-lignin units were preferentially degraded than guaiacyl (G)-lignin units, resulting in a decreased S/G ratio. A decreasing S/G ratio (wheat straw: r = −0.72, wood chips: r = −0.75) and selective lignin degradation (wheat straw: r = −0.69, wood chips: r = −0.88) were correlated with in vitro gas production (IVGP), a good indicator for rumen degradability.ConclusionsL. edodes treatment increased the IVGP of wheat straw and wood chips. Effects on IVGP were similar for wheat straw and wood chips indicating that lignin content and 3D-structure of cell walls influence in vitro rumen degradability more than lignin composition.
Highlights
The present work investigated the influence of lignin content and composition in the fungal treatment of lignocellulosic biomass in order to improve rumen degradability
Lignin composition is different for each plant species, for example, lignin in grasses and herbaceous plants consists of S, G, and p-hydroxyphenyl unit (H-unit), whereas softwoods present mainly G-lignin units and hardwoods present S- and G-units in different proportions [15]
During pyrolysis the plant material is heated at high temperatures in an oxygen-free environment to break down the macromolecular components of plant cell walls to smaller compounds, which are subsequently analyzed in a GC/MS system
Summary
The present work investigated the influence of lignin content and composition in the fungal treatment of lignocellulosic biomass in order to improve rumen degradability. Wheat straw and wood chips, differing in lignin composition, were treated with Lentinula edodes for 0, 2, 4, 8 and 12 wk and the changes occurring during fungal degradation were analyzed using pyrolysis-gas chromatography-mass spectrometry and detergent fiber analysis. Carbohydrates in plant cell walls can be an important source of nutrients for ruminants These carbohydrates are bound to lignin, which can be degraded only under aerobic conditions by fungi and some bacteria [1], and as such cannot be broken down in the low oxygen environment of the rumen. Py-GC/MS is a useful tool to monitor the extent of fungal degradation of lignocellulosic constituents, which cannot be straightforwardly detected with the standard gravimetric methods, such as the detergent fiber method [16,17,18]
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