Fermentation of pectin and glucose, and activity of pectin-degrading enzymes in the rabbit caecal bacterium Bacteroides caccae

AIMS: To compare fermentation pattern in cultures of Bacteroides caccae supplied with pectin and glucose, and identify enzymes involved in metabolism of pectin. METHODS AND RESULTS: A strain KWN isolated from the rabbit caecum was used. Fermentation pattern, changes of viscosity and enzyme reactions products were determined. Cultures grown on pectin produced significantly more acetate and less formate, lactate, fumarate and succinate than cultures grown on glucose. Production of cell dry matter and protein per gram of substrate used was the same in pectin- and glucose-grown cultures. The principal enzymes that participated in the metabolism of pectin were extracellular exopectate hydrolase (EC 3.2.1.67), extracellular endopectate lyase (EC 4.2.2.2) and cell-associated 2-keto-3-deoxy-6-phosphogluconate (KDPG) aldolase (EC 4.1.2.14). The latter enzyme is unique to the Entner-Doudoroff pathway. Activities of pectinolytic enzymes in cultures grown on glucose were low. Activity of KDPG aldolase was similar in pectin- and glucose-grown cells. CONCLUSIONS: Metabolites and activities of pectin-degrading enzymes differed in cultures of B. caccae KWN grown on pectin and glucose. Yields of dry matter and protein were the same on both substrates. SIGNIFICANCE AND IMPACT OF THE STUDY: Information on metabolism of pectin in animal strains of Bacteroides is incomplete. This study extends the knowledge on metabolism in bacteria from the rabbit caecum.