INFLUENCE OF CARBON-DIOXIDE ON LIGNIN DEGRADATION AND DIGESTIBILITY OF LIGNOCELLULOSICS TREATED WITH PLEUROTUS-SAJOR-CAJU

This study investigates the effect of different CO2 concentrations on lignin degradation and in vitro digestibility of wheat straw used as g rowth substrate for Pleurotus sajor-caju. The degradation of wheat str aw lignin by P. sajor-caju increased under the influence of CO2 (0-20% ) in the atmosphere and then started declining at higher levels. The m aximum loss of lignin (39.7%) was found in cultures grown with passive air exchange through cotton plugs while digestibility was higher in c ultures actively aerated with 0-30% CO2. Aside from gases, the period of incubation, i.e. 40 days rather than 20 days, seems to be the most important variable for improving the digestibility of the product. Gen erally, the process efficiency for change in digestibility per gram lo ss of organic matter enhanced from 0 to 30% CO2 at a fixed level of O2 (20%) in the gaseous phase.