An anaerobic chemostat that permits the collection and measurement of fermentation gases.

A chemostat was designed to allow anaerobic growth in the culture vessel in the absence of a continuous stream of O 2 -free gas. Produced gases were collected within the culture and collection vessels, and pressure build-up was prevented by allowing gases to expand into a collapsed football bladder. The culture overflow was collected in a flask, held at 0 C, that was emptied by applying a positive CO 2 pressure to the system. Ruminococcus albus , a H 2 and CO 2 -producing anaerobe, was used to test the operation of the apparatus. H 2 production was measured by sampling the various gas spaces of known volume and measuring H 2 concentration by gas chromatography. Measurement of accumulated fermentation gases and the effects of the accumulation on fermentations can be studied with the apparatus.