H 2 -CO 2 Recirculation and pH Control for Growth of Methanogens in Mass Culture

Abstract

We modified a fermentor (10-liter liquid volume) for the growth of anaerobic, H(2)-CO(2)-catabolizing bacteria. Gas in the fermentor (ca. 10% CO(2), 50% H(2), 40% CH(4)) was recirculated by a diaphragm pump. During growth, the gas composition was maintained by the addition of a mixture of 80% H(2) and 20% CO(2), and this addition was controlled by a pH auxostat. During gas addition, gas was discharged from the recirculating gas stream and was collected by the displacement of an acidified salt solution.