RESUMO
To identify optimal hydrogen production conditions using growing cultures of Rhodobacter sphaeroides DSM 158 the effects of varying the reactor's volumetric power input (0.01-1.4kWm(-3)) and irradiation intensity (5-2500Wm(-2)) were investigated in batch and continuous production modes. Irradiation intensity had a greater effect on hydrogen production than volumetric power input. Hydrogen production and photofermentative biomass formation were maximized by irradiation at 2250Wm(-2) with a volumetric power input of 0.55kWm(-3). The bacterial dry weight (2.64gL(-1)) and rate of hydrogen production (195mLL(-1)h(-1)) achieved under these conditions were greater than any that have previously been reported for batch-mode hydrogen production by R. sphaeroides. Continuous mode experiments (D=0.1h(-1)) yielded a bacterial dry weight, hydrogen production rate, productivity and hydrogen yield of 2.35±0.18gL(-1), 165±6.2mLL(-1)h(-1), 3.96LL(-1)d(-1) and 36.6%, respectively.
Assuntos
Hidrogênio/metabolismo , Fotobiorreatores/microbiologia , Rhodobacter sphaeroides/metabolismo , BiomassaRESUMO
Based on the p426 series of expression vectors developed by Mumberg et al. (Gene 156, 119-122, 1995), we have generated a set of plasmids that allow the glucose-dependent expression of target genes in the yeast, Saccharomyces cerevisiae. The ADH1 promoter in plasmid p426-ADH1 was replaced by the 1-kb 5'-region from either of the following genes: HXK1, YGR243, HXT4 and HXT7. Expression mediated by the respective 5'-regions was monitored with EGFP, yEGFP3-CLN2pest and TurboGFP as marker genes. Fluorescence is induced 2.7-fold using the HXK1, 2.3-fold using the YGR243-, 5-fold using the HXT7- and 12.6-fold using the HXT4 5'-regions upon depletion of glucose to a concentration of <0.5 g/l.