IN-VITRO INVESTIGATION ON THE GLYCEROL TR ANSFORMATION BY RUMEN MICROBES

Rumen fluid from sheep (non adapted to glycerol) was incubated up to s ix hours under anaerobic conditions with buffer and mineral solution. Wheat starch was added as substrate in an amount of 1g DM per vessel. Glycerol was additionally admitted to rumen fluid in amounts of 5 to 5 0% of starch. Carrierfree C-14-glycerol (1,3-labelled) or N-15-labelle d NH4Cl were added to different incubation vessels. The disappearance rate of glycerol depended from the amount of added glycerol and incuba tion time. More than 90% of glycerol disappeared in 2 hours (5% additi on), 4 hours (10% addition) and 6 hours (15 to 25% addition) respectiv ely. The sum of volatile fatty acids elevated significant with a highe r glycerol addition and 6 hours incubation time. The concentration of propionic acid increased also in dependence of the added glycerol amou nt and the longer incubation time. The proportion of acetic acid to pr opionic acid changed from high values (3.5 to 4.0, without glycerol) t o the lowest value from 2.5 after 6 hours incubation time and 25% glyc erol addition. The most radioactivity of added C-14-glycerol was found in propionic acid and only up to 11% in CO2. C-14-radioactivity was n ot detected in methan, lactic acid and acetic acid respectively. The N -15-labelling of TCA-precipitable N-fraction was not influenced by gly cerol supplementation but the N-15-incorporation in the bacterial nitr ogen fraction was lower in the vessels with glycerol.