It was reported that Laminaria japonica, one of the brown alga, contains mannitol and alginate in the ratio of 8 and 7% (to the gross wet weight), respectively. Therefore,15% of Laminaria biomass can be used as the substrate of fermentative hydrogen production. Furthermore, mannitol is readily taken by bacteria because of its hexose resemble structure. Mannitol has two more hydrogen molecules than glucose. From these features, mannitol has a good potential of H₂ production. However, alginate, polysaccharide, is a hard resolution material. It is necessary to make it low molecule to be taken by bacteria.
In this study, some new bacteria for hydrogen production from mannitol were screened and these capabilities of hydrogen production were measured. About 200 samples were included on the manitol containing plates. 25 samples formed colony on that plate. Secondly, batch cultivation from mannitol was carried out with these samples by using 500ml fermenter. The volume of medium was 450ml. The medium component is mannitol and ABCM SEMISOLID AGAR. And hydrogen production yield and amount of produced H₂ were investigated. From results, 3 samples were selected out of 25 samples. H₂ yield of newly screened bacteria was 2.3 mol-H₂/mol-mannitol while that of E. aerogenes was 1.6 mol-H₂/mol-mannitol.