Analyses of fungal fermentation of lignocellulosic substrates using continuous culture rumen simulation.

In vitro rumen digestibility of five lignocellulosic materials (rice bran, ryegrass-hay, barley straw, birch and spruce sawdusts) were assessed before and after solid substrate fermentations with Coriolus versicolor, Pleurotus sajo-caju, Phanerochaete chrysosporium, Chaetomium cellulolyticum, and Trichoderma harzianum. In studies with spruce sawdust, marked reductions in gas and volatile acid production were observed after 4 days of simulated rumen fermentation. With the fermented sawdusts, increases in digestibility and daily carbon dioxide production were observed as the fermentation proceeded. Chitin and D(+)-glucosamine, major components of fungal cell walls enhanced digestibility, acetate output and total gas production except at concentrations >30% w/w chitin or >1% w/v glucosamine which gave adverse results. The presence of high levels of mycelial biomass observed visually in fungal fermented rice bran, hay and barley straw did not appear to enhance digestibility.