Hydrogen Production in Anaerobic Biofilms

Abstract

Anaerobic syntrophic associations and microbially-induced hydrogen damage to metals depend on production and consumption of hydrogen. In both instances, hydrogen-producing bacteria such as homoacetogens and other fermentors are present. In syntrophy, hydrogen is directly transferred to bacteria such as methanogens which, by the consumption of hydrogen, permit the otherwise thermodynamica1ly unfavorable hydrogen production reaction to occur. Hydrogen damage to metal results from entry of atomic hydrogen into the metal lattice. The atomic hydrogen recombines at irregularities in the metal to form gaseous molecular hydrogen. Cracks then propagate, leading to loss of ductility and premature failure of metal structures. In both cases, gaseous and dissolved hydrogen concentrations are found to be lower than predicted by rates of methanogenesis¹ and metal corrosion. To our knowledge, no techniques have yet been developed to measure hydrogen production within the tightly coupled community of anaerobic biofilms.