Renewable algal photo H2 production without S control using acetate enriched fermenter effluents

Abstract

Listen

Translate article

Renewable energy production using microorganisms is one of the challenging issues for environmental sustainability. Algal hydrogen (H2) production has often been achieved by sulfur (S) and chloride ion (Cl−) deprivation in a growth medium; however, it may not be realistic to control S or Cl− concentrations in natural sources (e.g., wastewater). In this study, two different green algal species, Chlamydomonas reinhardtii and Chlorella sorokiniana were selected and their photosynthetic activities were compared with different acetate/Cl− ratios both in batch and continuous modes. At 150 of acetate/Cl− ratio, the H2 production rates were 0.25–0.33 μmol L−1 min−1 for C. sorokiniana and 0.20–0.38 μmol L−1 min−1 for C. reinhardtii, respectively. The hydrogenase (HydA) reactivation and photosystem II (PSII) inhibitor test revealed that biohydrogen production by algae is due to photosynthetic activity. It was found that maintaining acetate/Cl− ratios greater than 60–100 leads to continuous O2 depletion and thus renewable H2 production for both algal species. Molecular dynamics (MD) simulations of hydrogen bonding between Yz and His190 in PSII supported O2 inhibition using acetate. Using fermenter effluents, C. sorokiniana and C. reinhardtii showed a successful continuous H2 production of ~80 μmol L−1 and ~95 μmol L−1, respectively, for 15 days.