Microalgal community and their growth conditions influence biohydrogen production during integration of dark-fermentation and photo-fermentation processes

Nature and survivability of microalgal population during growth and photofermentative hydrogen (H2) production was evaluated using acid-rich effluents generated from dark-fermentation. Microalgae enriched in presence of glucose showed the dominance of H2 producing Chlorella sp. (Consortia-A), while consortia under starvation had the dominance of Scenedesmus sp. and Diatoms (Consortia-B) with negligible H2 production. Further experiments with Consortia-A using acid-rich effluents of designed synthetic wastewater (DSW) and food waste (FW) showed higher H2 production in the former than the latter in both dark (DSW, 1.21 mmol; FW, 0.16 mmol) and photo (DSW, 5.22 mmol; FW, 1.24 mmol) fermentation. High acetate concentrations in DSW effluents favored H2 production over FW effluents. Substrate degradation was also higher in case of DSW than the FW sets. Microalgal population that dominanted in Consortia-B appears to have opted the lipid storing metabolic pathway evidencing 2% lipid that can be converted to biodiesel. The data represent a novel approach to exploiting microalgae for biohydrogen production at the expense of cheaper raw material like dark-fermentation effluents.

► Integration process of dark-fermentation with photo-fermentations was evaluated based on microalgal community analysis. ► Effluents with higher acetate showed higher hydrogen production during photo fermentation. ► Cultures enriched with glucose showed dominance of hydrogen producing Chlorella sp. ► Cultures under starvation, favored growth of Senedesmus sp and diatoms with lipid accumulation pathway.