A small-scale, three-vessel, continuous culture system for quantitative studies of plant fibre degradation by anaerobic bacteria

Abstract

A continuous culture system is described which consists of three all-glass water-jacketted culture vessels of ≈250 ml capacity, linked by electro-pneumatic valves and medium lines of low hold-up volume to a common, spherical medium reservoir. The contents of the reservoir and the culture vessels are agitated by efficient vibratory stirrers to keep the insoluble substrate in homogeneous suspension, and are blanketed against contact with atmospheric O 2 by slow purging with a stream of O 2-free gas mixture containing 5% H 2, 30% CO 2 and 65% N 2. Medium is dosed to the culture vessels by periodic activation of the pneumatic valves, and corresponding volumes of culture are displaced into sterile harvest vessels via lateral exit ports with the aid of a slow flow of anaerobic gas through the culture vessels. Both pH auxostat (as defined by Martin and Hempfling [1]) and chemostat operation are possible. Performance specifications of the system are given and the usefulness of the system for investigations of the kinetics of growth on, and utilization of, solid substrates is illustrated by results obtained with one strain each of Ruminococcus flavefaciens and Fibrobacter (Bacteroides) succinogenes, grown on ball-milled filter paper cellulose.