Transformation of wheat straw in the course of solid-state fermentation byfour ligninolytic basidiomycetes

Biological upgrading of wheat straw by the white-rot fungi Phanerochaete ch rysosporium, Pleurotus eryngii, Phlebia radiata, and Ceriporiopsis subvermi spora was monitored during 60-day solid-state fermentation. Analysis of str aw included determination of weight loss and lignin content, color analysis , and infrared spectroscopy, whereas the studies on the water-soluble fract ions were carried out by infrared spectroscopy, elementary analyses and qua ntification of the total phenols and reducing sugars. The most selective de gradation of lignin was produced by P. eryngii and especially by IC subverm ispora, the former species releasing the greatest amount of colored water-s oluble products, whereas an increase in straw brightness was caused by C. s ubvermispora. In general, the composition of the water-soluble fraction cor related with the extent of straw transformation. The initial fermentation s tage (0-15 days) was characterized by the accumulation of water-soluble pro ducts from lignin degradation and fungal metabolism, the concentration of w hich tended to stabilize in the second stage (16-60 days). The degree of de lignification at the second stage tended to coincide with the decrease of t he water-soluble nitrogen. (C) 1999 Elsevier Science Inc. All rights reserv ed.