Biohydrogen production from glucose, molasses and cheese whey by suspended and attached cells of four hyperthermophilic Thermotoga strains

BACKGROUND: Bio-hydrogen production from organic residues is an attractive process that combines energy generation with waste treatment. This work describes hydrogen production from molasses and cheese whey by biofilm and suspended-cells of 4 hyperthermophilic Thermotoga spp. For the best performing strain, a preliminary process optimization was performed. RESULTS: In experiments with glucose-fed T. neapolitana, HEPES resulted the best-performing buffer, whereas the highest H2 rate was obtained with the biofilm support exposing the highest specific surface. All the Thermotoga strains tested (T. neapolitana, T. maritima, T. naphtophila, T. petrophila) were able to produce H2 from glucose, molasses and cheese whey under both suspended- and attached-cell conditions. T. neapolitana resulted the best H2 producer with all the three substrates. The best H2 production rate was higher on molasses (1.7 mmol H2 / L medium / h) than on cheese whey (0.94 mmol H2 / L medium / h), whereas the highest H2/substrate yields were similar between the two substrates (2.95 mol H2 / mol monosaccharide consumed on molasses and 2.50 mol H2 / mol monosaccharide consumed on cheese whey). With both wastes, the progressive growth medium simplification allowed a drastic reduction of medium cost, without significant losses of process performance. CONCLUSION: Both molasses and cheese whey are suitable substrates for H2 production by suspended- and attached-cells of Thermotoga species.