EFFECTS OF CELL-WALL PHENOLICS AND FUNGAL METABOLITES ON METHANE AND ACETATE PRODUCTION UNDER IN-VITRO RUMEN CONDITIONS

The effects of cell wall phenolics, lignins and fungal metabolites on end products of simulated rumen fermentations were studied. Monomeric phenolics, selected to represent the products of aerobic oxidation of lignin by fungi, slightly enhanced carbon dioxide output at low concen trations (0.05%) but had no stimulatory effect on acetate production. Higher concentrations (0.5%) of industrial and Klason lignin decreased carbon dioxide, methane, acetate and propionate production. Secondary metabolites from toxigenic strains of Aspergillus flavus, which were used to simulate the presence of contaminated feedstuff arising from n on-sterile fungal bioconversion systems (fermentations), stimulated ca rbon dioxide, methane, acetate and propionate production but not when extracts were boiled or autoclaved. Acetate, propionate, methane and c arbon dioxide production were only slightly reduced in the presence of purified aflatoxin. With spruce sawdusts pretreated with fungi, it wa s found that accumulation of soluble compounds from lignin and polysac charide depolymerisations in rumen simulations were markedly higher wi th sawdusts pretreated with fungi under non-sterile conditions. It was concluded that fungal pretreatment of lignocellulosic substrates had no adverse effects on the end products of rumen fermentations.