INHIBITION OF METHANOGENESIS BY SEVERAL HEAVY-METALS USING PURE CULTURES

The effect of different concentrations of nickel, copper and zinc on m ethanogenesis using pure cultures of Methanobacterium formicicum, Meth anobrevibacter arboriphilicus, Methanosarcina thermophila and Methanos pirillum hungatei over time (1, 15 and 30 d) was evaluated. Methanobac terium formicicum showed the highest resistance to all the metals test ed, while Methanospirillum hungatei was the most sensitive strain. All strains were sensitive to copper and zinc (10-250 mg l(-1)), but were much more resistant to nickel (200-1200 mg l(-1)). An adaptation proc ess of the methanogenic pure cultures with the toxicants was observed over time, which indicates that the inhibitory effect of heavy metals may be reverted in optimal anaerobic conditions.