초록
<P><B>Abstract</B></P> <P>Wheat straw and oak wood chips were incubated with <I>Ceriporiopsis subvermispora</I> and <I>Lentinula edodes</I> for 8 weeks. Samples from the fungal treated substrates were collected every week for chemical characterization. <I>L. edodes</I> continuously grew during the 8 weeks on both wheat straw and oak wood chips, as determined by the ergosterol mass fraction of the dry biomass. <I>C. subvermispora</I> colonized both substrates during the first week, stopped growing on oak wood chips, and resumed growth after 6 weeks on wheat straw. Detergent fiber analysis and pyrolysis coupled to gas chromatography/mass spectrometry showed a selective lignin degradation in wheat straw, although some carbohydrates were also degraded. <I>L. edodes</I> continuously degraded lignin and hemicelluloses in wheat straw while <I>C. subvermispora</I> degraded lignin and hemicelluloses only during the first 5 weeks of treatment after which cellulose degradation started. Both fungi selectively degraded lignin in wood chips. After 4 weeks of treatment, no significant changes in chemical composition were detected. In contrast to <I>L. edodes</I>, <I>C. subvermispora</I> produced alkylitaconic acids during fungal treatment, which paralleled the degradation and modification of lignin indicating the importance of these compounds in delignification. Light microscopy visualized a dense structure of wood chips which was difficult to penetrate by the fungi, explaining the relative lower lignin degradation compared to wheat straw measured by chemical analysis. All these changes resulted in an increased in <I>in vitro</I> rumen degradability of wheat straw and oak wood chips. In addition, more glucose and xylose were released after enzymatic saccharification of fungal treated wheat straw compared to untreated material.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Combining chemical, visual and utilization analysis shows fungal delignification. </LI> <LI> Formation of fungal biomass does not always follow degradation of lignocellulose. </LI> <LI> <I>C. subvermispora</I> and <I>L. edodes</I> have a different mechanism of lignin degradation. </LI> <LI> Fungal treatment results in an increased utilization of wheat straw and wood chips. </LI> <LI> Alkylitaconic acids production is important for selective delignification. </LI> <LI> Density of the tissue limits fungal delignification. </LI> </UL> </P>