Comparative degradation of hydrothermal pretreated winery grape wastes by various fungi

Hydrothermal-treated (autoclaved) winery waste was degraded by Trichoderma harzianum, Aspergillus niger, Penicillium chrysogenum and Penicillium citrinum. Quantification of lignins, reducing sugars, pentoses and enzyme assays for cellulase, β-glucosidase and xylanase were performed. Lignin content increased from 36% in untreated waste to 63% in autoclaved substrate. Lignin degradation of 9% and 4.2% was achieved by P. chrysogenum and A. niger, respectively. Reducing sugars decreased by 1.2 and 0.7 kg/m3 in T. harzianum and P. citrinum cultures, respectively. Pentose utilization was also considerable across all cultures. Cellulase and xylanase activities were higher in A. niger cultures at 45 U and 335 U, respectively. It also showed high β-glucosidase activity of 155 U, marginally less than P. citrinum (180 U). Autoclaving hydrolyzed hemicelluloses and crystalline cellulose, converting the latter to a more degradable amorphous form. The results suggest that successive hydrothermal and fungal treatments produce greater lignocellulose degradation than regular fermentation.