Combination of dark- and photo-fermentation to improve hydrogen production from Arthrospira platensis wet biomass with ammonium removal by zeolite

Arthrospira platensis wet biomass was subjected to microwave-assisted dilute H2SO4 pretreatment to improve saccharification by hydrolysis with glucoamylase and hydrogen production from dark-fermentation. When the hydrolyzed biomass from A. platensis was inoculated with hydrogenogens (heat-treated anaerobic sludge) to produce hydrogen during dark-fermentation, the maximum hydrogen yield of 96.6 ml H2/g DW was obtained. Because high concentration of NH4+ (31.6–56.5 mM) in the residual solution (also containing acetate and butyrate) obtained from dark-fermentation can significantly inhibit the activities of photosynthetic bacteria in sequential photo-fermentation, a modified zeolite was used to extract NH4+ by ion exchange to reduce the NH4+ content to 2.2–2.7 mM (91.8%–95.8% of NH4+ removal efficiency). The treated residual solution was reused for hydrogen production in sequential photo-fermentation. The maximum hydrogen yield from A. platensis wet biomass was significantly enhanced from 96.6 to 337.0 ml H2/g DW using a combination of dark- and photo-fermentation. ► Arthrospira platensis wet biomass is microwaved with acid to improve enzymatic hydrolysis. ► Hydrolyzed microalgae is fermented by hydrogenogens to enhance dark H2 yield. ► NH4+ removal by zeolite between the dark- and photo-fermentation improved H2 yield. ► H2 yield is markedly enhanced from microalgae by dark- and photo-fermentation.