Production of Hydrogen from α-1,4- and β-1,4-Linked Saccharides by Marine Hyperthermophilic Archaea

Abstract

ABSTRACT Nineteen hyperthermophilic heterotrophs from deep-sea hydrothermal vents, plus the control organism Pyrococcus furiosus , were examined for their ability to grow and produce H 2 on maltose, cellobiose, and peptides and for the presence of the genes encoding proteins that hydrolyze starch and cellulose. All of the strains grew on these disaccharides and peptides and converted maltose and peptides to H 2 even when elemental sulfur was present as a terminal electron acceptor. Half of the strains had at least one gene for an extracellular starch hydrolase, but only P. furiosus had a gene for an extracellular β-1,4-endoglucanase. P. furiosus was serially adapted for growth on CF11 cellulose and H 2 production, which is the first reported instance of hyperthermophilic growth on cellulose, with a doubling time of 64 min. Cell-specific H 2 production rates were 29 fmol, 37 fmol, and 54 fmol of H 2 produced cell −1 doubling −1 on α-1,4-linked sugars, β-1,4-linked sugars, and peptides, respectively. The highest total community H 2 production rate came from growth on starch (2.6 mM H 2 produced h −1 ). Hyperthermophilic heterotrophs may serve as an important alternate source of H 2 for hydrogenotrophic microorganisms in low-H 2 hydrothermal environments, and some are candidates for H 2 bioenergy production in bioreactors.