Enhanced hydrogen production by a newly described heterotrophic marine bacterium, Vibrio tritonius strain AM2, using seaweed as the feedstock

To achieve more stable bio-hydrogen (bioH sub(2)) production from non-food feedstocks, stable feedstock preparations of marine biomass and an efficient bioH sub(2) system using marine bacteria under saline conditions are two important key technologies that needed to be developed. Vibrio tritonius strain AM2, which was isolated from the gut of a marine invertebrate, was cultured under various conditions in marine broth (at initial 2.25% (w/v) NaCl) supplemented with mannitol, a seaweed carbohydrate, to evaluate its hydrogen production. The maximum molar yield of bioH sub(2) was recorded as 1.7 mol H sub(2)/mol mannitol at pH 6 and 37 degree C. The mannitol-grown cells had higher yields of bioH sub(2) than the glucose-grown cells in the pH range 5.5-7.5. Compared to glucose, mannitol might be a better substrate for bioH sub(2) production using strain AM2. Fermentation product profiling revealed that strain AM2 might be utilising the formate-hydrogen pathway for bioH sub(2) production. Furthermore, strain AM2 was able to produce hydrogen from powdered brown macroalgae containing 31.1% dry weight of mannitol. The molar yield of hydrogen reached 1.6 mol H sub(2)/mol mannitol contained in the seaweed feedstock. In conclusion, strain AM2 has the ability to produce hydrogen from mannitol with high yields even under saline conditions.