Hydroxyapatite for Enhancing Biohydrogen Production from Dark Fermentation

Hydroxyapatite (HA) was synthesized by co-precipitation and characterized for biohydrogen (BioH2) production. The highest BioH2 yield obtained was 182.33±2.41 mL/g glucose, amended with an optimal dosage of 400 mg/L HA, which was 55.80% higher BioH2 yield compared with the control group without any addition (p<0.05). The results indicated that HA facilitated the deterioration of organic substances and increased the concentration of soluble microbial products (SMPs). Microbial community analysis revealed that HA significantly increased the abundance of Firmicutes from 35.27% (0 mg/L, HA) to 76.41% (400 mg/L, HA), which play an essential role in BioH2 generation. In particular, the abundance of Clostridium sensu stricto 1 increased from 15.33% (0 mg/L HA) to 45.17% (400 mg/L HA), and became the dominant bacteria. This also revealed appropriate concentrations of HA could significantly improve BioH2 production.