Analysis of a highly efficient methanogenic consortium producing biogas from whey

Abstract

Ninety % of the bacterial population of an anaerobic whey digester were isolated and characterized. Fifty-five % of the isolates were fermentative, 5% acetogenic and 40% methanogenic organisms. Of the fermentative isolates, one strain of Lactobacillus , three strains of Eubacterium and 2 strains that could not be assigned to any known genus were predominant, accounting for 45% of the culturable population. The remaining 10% of the fermentative strains comprised Clostridia, Fusobacterium and Bacteroides . Each of these isolates represented less than 2% of the culturable population. The isolates probably belonging to the acetogenic stage could be assigned to Desulfovibrio and constituted approximately 5% of the culturable population. The methanogens consisted of 5 morphologically different groups. One group had the characteristic morphology of Methanospirilium , but no strains were isolated. Isolates of the other 4 groups were identified as strains of Methanobacterium formicicum, Methanobrevibacter arboriphilus, Methanothrix soehngenii and Methanocorpusculum parvum ( Zellner et al., 1987). On the basis of the metabolic capabilities of the isolates a microbial food chain for the degradation of the whey components to methane and CO 2 is proposed, fitting the theoretical model of Bryant (1979).