SOLUBILIZATION OF CELLULOSE BY MESOPHILIC CELLULOLYTIC CLOSTRIDIA ISOLATED FROM A MUNICIPAL SOLID-WASTE DIGESTER

Six cellulolytic mesophilic clostridia, isolated from a municipal solid-waste digester, were studied on cellobiose and on three different celluloses (filter paper, MN.300 and Avicel cellulose powder) as energy and carbon sources. Doubling times during growth on cellobiose and cellulose were 3 h and 13-26 h, respectively. In all cases, a large percentage of the cellulose was metabolized, averaging 70% of initial cellulose (7.5 g litre-1). All strains produced a high activity of CMCases in the three cellulose media. The main fermentation products were acetate, ethanol and CO2. Less than 0.25 g litre-1 of reducing sugars was accumulated, with glucose accounting for 5-10%.