To date, practical methods of improving the digestibility of straw are largely confined to treatment with alkalis (Sundstol and Owen, 1984). Though effective, these chemicals can be hazardous for on-farm use and are potential pollutants. Biological methods of upgrading straw using fungi or enzymes (Zadrazil, 1984) would be less hazardous and more acceptable if practical and economic techniques could be developed. The present experiment examined the potential of ligninase enzyme produced from the fungus Phanerochaete ohrysosporium for upgrading straws. The aim was to define treatment conditions required. Treatment with sodium hydroxide was included as a positive control. Treatment effects were assessed by measuring changes in digestibility in vitro and chemical composition.
Seventy two treatments were compared. 10 g samples of milled (1.0 mm) straw were immersed (ambient temperature 15°C) in 100 ml buffered (pH 3.5) solution, with one of four levels of ligninase (zero; 0.1 unit/10 g straw; 1.0 unit; 10 units; one unit of enzyme oxidises 1 μmol veratryl alcohol to veratraldehyde per minute, at pH 2.75), with or without hydrogen peroxide (ligninase depends on H2O2 for its oxidative reaction), veratryl alcohol (used to induce the ligninase production and activity), or both of them.