초록
Hydrogen gas (H<SUB>2</SUB>) production was studied in bacteria cultured at different pH conditions, and on different carbon substrates. H<SUB>2</SUB> production by Escherichia coli was first studied during glycerol fermentation when external formate (10 mM) was supplemented. Changes in H<SUB>2</SUB> production rate (V<SUB>H2</SUB>) were determined when in the assays glycerol and/or formate were supplemented at pH 7.5 and pH 6.5, using single and double mutants coding large subunits of different hydrogenases (Hyd-1, Hyd-2 and Hyd-3) as well as selC (coding for formate dehydrogenases), hyaB hybC (coding for large subunits of Hyd-1 and Hyd-2, respectively) selC or hyaB hybC hycE (coding for large subunit of Hyd-3) triple mutants at both pHs. The results point out that Hyd-3 becomes mainly responsible for H<SUB>2</SUB> production by E. coli during glycerol fermentation when external formate is added; Hyd-4 can also contribute to H<SUB>2</SUB> production. Besides, in the glycerol supplemented assays, three hydrogenases can work in H<SUB>2</SUB> producing mode and only deletion of three of them decreases the production of H<SUB>2</SUB> which might be due to disturbance of H<SUB>2</SUB> cycling. This is of significance in application of different carbon sources in renewable energy production technology using bacteria.