Formation of polysaccharide depolymerase and glycoside hydrolase enzymes byBacteroides ruminicola subsp.ruminicola grown in batch and continuous culture

Abstract

The activity of ten polysaccharide depolymerase and glycoside hydrolase enzymes was monitored inBacteroides ruminicola subsp.ruminicola throughout the growth cycle and over a range of dilution rates in carbon-limited continuous (chemostat) culture. The enzymes were principally cell associated, and the specific activities increased throughout the growth cycle to reach maximum levels in the late exponential and stationary growth phases. In chemostat-grown cells the activities were growth rate dependent and were highest at the lowest dilution rates examined (0.025/h), but remained constant over a wide range of growth rates (D=0.05–0.15/h). The specific activities were lower in cells with a generation time of 3 h (D=0.225/h). The major metabolites formed from xylose, in batch and continuous culture, were lactic, acetic, and succinic acids, with traces (∼1%–2% of total acid production) of branched and straight-chain C3−C5 volatile fatty acids. The proportions of the metabolites produced varied with the stage and rate of growth.