Fermentation of Acetate

Abstract

It was 100 years after the discovery of “combustible air” by Alessandro Volta in 1776 that acetate was first implicated as a substrate for methanogenesis. In 1876, Hoppe-Seyler demonstrated that sewage sludge produced methane when amended with acetate. Later, Hoppe-Seyler (1887) showed that enrichment cultures converted the substrate to equimolar amounts of methane and carbon dioxide. Nearly 40 years later, Söehngen (1906) described Gram-negative sarcina and a filamentous rod-shaped microorganism in acetate-utilizing enrichment cultures. However, nearly another 40 years elapsed before Schnellen (1947) described the first pure cultures (of Methanosarcina barken) which grew on acetate. Growth was slow and subsequent isolates also produced methane from acetate at rates which were considered too low to account for methanogenesis in the environment. As a result, it was hypothesized that cocultures were required for the rapid conversion of acetate to methane. During the 1960s, it became evident that most of the methane in freshwater environments is derived from acetate (Jeris and McCarty, 1965; Smith and Mah, 1966), a development which created a renewed interest in methanogenic acetotrophs. In the late 1970s and early 1980s, it was shown that pure cultures of Methanosarcina converted acetate to methane and carbon dioxide in defined media and at rates much greater than previously reported (Mah et al., 1978; Weimer and Zeikus, 1978; Smith and Mah, 1980).