Monitoring of Methanogenic and Acidogenic Microbial Populations in the Liquefying Compartment of the MELiSSA Loop

The Micro-Ecological Life Support System Alternative (MELiSSA) is a bioregenerative system which basically transforms organic wastes into oxygen and food. In the first of five compartments, insoluble organic matter is liquefied in anaerobic thermophilic conditions. Because volatile fatty acids are needed for biotransformations in downstream compartments, methanogenesis is inhibited by acidification. In the present paper we monitored the stability of the microbial communities by DGGE fingerprinting. Flexible acidogenic populations seemed to relate to stable reactor performance. Organisms present showed high similarity to fecal or cellulolytic or fatty-acid producing bacteria. Methanogenic bacteria remained present and resumed activity when acidification was interrupted.