High-productivity hydrogen production via bioaugmentation of exogenous Clostridium species using a red algal biomass (Eucheuma spinosum)

Abstract

This study demonstrated the high-productivity hydrogen production via Clostridium pasteurianum bioaugmentation from algal biomass (Eucheuma spinosum) using a dynamic membrane bioreactor (DMBR). During the algal biomass supplementation without bioaugmentation, bio-H₂ production rate (HPR) and bio-H₂ yield (HY) were significantly decreased from 59.4 ± 3.0 L H₂/L-d and 2.35 ± 0.14 mol H₂/mol hexose_consumed to 15.6 ± 2.8 L H₂/L-d and 0.73 ± 0.13 mol H₂/mol hexose_consumed, respectively. This result indicated that algal biomass contributed to the extracellular polymeric substances (EPS) composition from polysaccharide-EPS to protein-EPS, and shifted the metabolic flux from H₂-producing pathways toward H₂-consuming and non-H₂-producing pathways. On the other hand, fermenter deterioration was significantly mitigated during the algal biomass supplementation with bioaugmentation, achieving an HPR and HY of 33.3 ± 3.3 L H₂/L-d and 1.57 ± 0.15 mol H₂/mol hexose_consumed, respectively. This result demonstrated that the bioaugmentation not only significantly enhanced polysaccharide-EPS formation but also substantially suppressed propionate- and formate-producing pathway under algal biomass conditions. Furthermore, this study observed that the deteriorated fermenter could be effectively recovered by bioaugmentation along with the synthetic substrate supplementation, owing to enhanced polysaccharide-EPS formation and the suppression of competitors. This study would offer a promising strategy to achieve the high-productivity hydrogen production via Clostridium pasteurianum bioaugmentation using algal biomass. This outcome would provide practical implications for the design and operation of dark fermentative hydrogen production from a red algal biomass, and further optimization of bioaugmentation strategies targeting EPS composition and competitors may enable more robust and scalable bio-H₂ production from algal biomass.