Graphene/hydroxyapatite nano-composite for enhancement of hydrogen productivity from delignified duckweed

The incredible growth of the duckweed (DW) in the water ecosystem causes severe environmental problems and reduces biodiversity. Harvesting and valorization of such plants represents a challenge due to its richness with organics. Hydrogen productivity (HP) from dark fermentation of delignified duckweed (DDW) is the main objective of current research. The anaerobes cultures were immobilized on the Graphene/hydroxyapatite nano-composite (nG/HAP) for enhancement of hydrogen yield (HY) and enzymes activities. The HP of 13.5 ± 0.78 mL was obtained from the fermentation of native DW and significantly increased up to 208.9 ± 12.6 mL for delignified one. This was linked to an increase of the hydrogenase enzyme (HE) activities from 0.02 ± 0.0003 to 0.109 ± 0.004 mg M.B reduced/min. The HP was further increased up to 387.1 ± 13.6 mL for batches containing 80 mg/gVS of nG/HAP. nG/HAP inhibited the competitors and promoted the cooperators for the Firmicutes hydrogen producers.