Influence of substrate concentration on the stability and yield of continuous biohydrogen production

G. Kyazze*, N. Martinez-Perez, R. Dinsdale, G. C. Premier, F. R. Hawkes, A. J. Guwy, D. L. Hawkes

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review


    The effect of substrate concentration (sucrose) on the stability and yield of a continuous fermentative process producing hydrogen was studied. High substrate concentrations are attractive from an energy standpoint as they would minimise the energy required for heating. The reactor was a CSTR; temperature was maintained at 35°C; pH was controlled between 5.2 and 5.3, and the hydraulic retention time (HRT) was 12 h. Online measurements were taken for ORP, pH, temperature, %CO2, gas output and %H2, and data logged using a MatLAB® data acquisition toolbox. Steady-state operation was obtained at 10, 20 and 40 g/L of sucrose in the influent, but a subsequent step change to 50 g/L was unsustainable. The hydrogen content ranged between 50% and 60%. The yield of hydrogen decreased as the substrate concentration increased from 1.7 ± 0.2 mol/mol hexose added at 10 g/L, to 0.8 ± 0.1 mol/mol at 50 g/L. Sparging with nitrogen improved the hydrogen yield by at least 35% at 40 g/L and at least 33% at 50 g/L sucrose. Sparging also enabled steady-state operation at 50 g/L sucrose. Addition of an extra 4 g/L of n-butyric acid to the reactor operating at 40 g/L sucrose increased the butyrate concentration from 9,830 to 18,900 mg/L, immediately stopping gas production and initiating the production of propionate, whilst the addition of 2 g/L taking the butyrate concentration to 12,200 mg/L did not do so. It was shown that operation at 50 g/L sucrose in a CSTR in butyrate fermentation is possible.

    Original languageEnglish
    Pages (from-to)971-979
    Number of pages9
    JournalBiotechnology and Bioengineering
    Issue number5
    Publication statusPublished - 5 Apr 2006


    • Biological hydrogen production
    • Butyrate inhibition
    • Hydrogen yield
    • Sparging
    • Stability
    • Substrate concentration


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