Effect of growth rate on the lipase activity of a rumen bacterium.

Abstract

IN 1961 Hobson and Mann1 reported the isolation of lipolytic bacteria from the sheep rumen. The predominant lipolytic bacteria were anaerobic, Gram-negative, vibrio-shaped organisms which were not named. Since this time other strains of these bacteria have been isolated and one (strain 5S) is being used in a detailed investigation of the lipolytic enzymes. Lipase activity was found to be associated with growing cells in batch culture and so the enzyme activity of the cells grown in continuous culture was tested so that the optimum activity might be obtained for further investigations. The bacterium was grown anaerobically in a medium as previously described2 and in a chemostat essentially similar to that described by Hobson3, but of larger vessel volume and fitted with a pH control system. In the results described here fructose (concentration 29 µmol/ml.) was the limiting nutrient, and the culture pH was controlled at 6.1–6.2, but similar results were found when glycerol was the limiting nutrient. The organism had previously been shown to hydrolyse glycerol esters of short-chain and long-chain fatty acids (tributyrin, triolein and linseed oil) but a more rapid enzyme assay was obtained using the method of Nachlas and Seligman4 in which hydrolysis of the naphthyl esters of acetic, lauric and stearic acids is followed. The results are taken from a continuous culture run of 1,100 h, and when the culture had stabilized at each growth rate a sample (10 ml.) was taken from the culture vessel and centrifuged to compact the cells. The supernatant was pipetted off and the cells resuspended in 1.0 ml. of Veronal buffer, pH 6.8, containing 0.02 per cent (w/v) sodium sulphide.