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

Abstract

Nature and survivability of microalgal population during growth and photofermentative hydrogen (H 2) production was evaluated using acid-rich effluents generated from dark-fermentation. Microalgae enriched in presence of glucose showed the dominance of H 2 producing Chlorella sp. (Consortia-A), while consortia under starvation had the dominance of Scenedesmus sp. and Diatoms (Consortia-B) with negligible H 2 production. Further experiments with Consortia-A using acid-rich effluents of designed synthetic wastewater (DSW) and food waste (FW) showed higher H 2 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 H 2 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.